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İSTANBUL TECHNICAL UNIVERSITY « INSTITUTE OF SCIENCE AND TECHNOLOGY
M.Sc. Thesis by Bülent ERİMAN
Department : Polymer Science and Technology
Programme: Polymer Science and Technology
May 2008
EFFECT OF THE POLYETHYLENE GRAFT COPOLYMER TO STRUCTURES AND
MECHANICAL PROPERTIES OF POLYETHYLENE/CLAY NANOCOMPOSITES
II
ACKNOWLEDGEMENT
First and foremost I would like to express my indebtedness to my advisor Prof. Dr.
Nurseli Uyanık who has supported and encouraged me from the very beginning of
this study and shared her deep knowledge and experience.
I would like to thank to Prof.Dr. Mine Yurtsever and her Ph.D. Student Erol Yıldırım
during the study of our project.
I would like to thank to Prof. Dr. Hulusi Özkul to allow us to use tensile testing
device.
I would like to thank to Gülnur Başer and my other lab. collaborator for their
contribution during the study.
The authors wish to thank Süd-Chemie Inc. for supplying Na MMT, Nanofil 757
used. This research was supported from The Scientific and Technological Research
Council of Turkey (Grant No. 105M049).
Finally, I would like to offer the most gratitude to my brother, my parents and my
fiancee who have always supported me during my whole life.
May 2008 Bülent Eriman
III
TABLE OF CONTENTS
ACKNOWLEDMENT……………………………………………………… ii
TABLE OF CONTENTS…………………………………………………… iii
LIST OF TABLES ……………………………………………………….… vi
LIST OF FIGURES ………………………………………………….……... vii
LIST OF SYMBOLS …………………………………………………….…. ix
SUMMARY …………………………………………………………………. xi
ÖZET ……………………………………………………………..………….. xviii
1.INTRODUCTION.................................................................................…… 1
2.THEORETICAL PART...........................................................................… 3
2.1. Clay Minerals………………………………………………………….. 3
2.1.1. Slicate Mineral Structures………….………….……………..…….. 4
2.1.2. Classification of Clay Minerals…...………..…..………...………… 5
2.1.2.1. Caolinit Group……………………….………………………… 6
2.1.2.2. Illit group …….……..…………………………………………. 6
2.1.2.3. Clorit group…...….…………………………………………….. 6
2.1.2.4. Smectite group…………………………………………………. 6
2.1.3. Cation Exchange Capacity…….…………………………………… 9
2.1.3.2. Inter layer Formation……..………….………………………... 10
2.2. Polyolefines…………………………………………………………… 12
2.2.1. Polyethylenes……………….……………………………………… 12
2.2.1.1. Low Density Polyethylene (LDPE) ..…..……………………… 12
2.2.1.2. Linear Low Density Polyethylene (LLDPE) ………………..… 13
2.2.1.3. Other Polyolefins………………………………………………. 14
2.2.2. Properties of Poliolefins………………….…..……………….…… 14
2.2.2.1. Mechanical Properties Of Polyolefins…………..……………… 16
2.2.2.2. Dielectric……………………………………………...………... 16
2.2.2.3. Density………………………………………………………….. 16
2.2.2.4. Melt Flow Index……………………...….……………………... 17
2.3. Compatibilizer……….………………………………………………... 19
2.3.1.Compatibility and Compatibilizers…………….………….………… 19
IV
2.3.2. Classification According to Prep. and Prop. of Compatibilizers…... 21
2.3.3. Works on IA/MMI/MAH Grafting Polyolefins in Recent Years…... 22
2.4. Polymer Nanocomposites ……..……………………………………… 23
2.4.1. Polymer nanocomposite Synthesis Methods ……..………………... 24
2.4.1.1. Melt Blending Synthesis…...………..………………………….. 24
2.4.1.2. Solvent Based Synthesis…….…………….…………………… 25
2.4.1.3. In-situ Polymerisation……..……………….…………………... 25
2.4.2. The structure of Nanocomposites …………..….….………………. 26
2.4.3. Structural Characterization of PNCs …………………….………… 29
2.4.4. Works on PNC including MAH/EVA Grafting Polyolefins ………. 32
3. EXPERIMENTAL PART………………………………………………… 37
3.1. Chemicals Used……………..………………………………………… 37
3.1.1. Low Density Polyethylene (LDPE) …………….…………………. 37
3.1.2. Linear Low Density Polyethylene (LLDPE)……………….……… 37
3.1.3. Itaconic Acid ………………………………………..……………... 37
3.1.4. Itaconic Monoesters ………………………………………………. 37
3.1.5. Sodium Montmorillonite………………………..………………….. 37
3.1.6. Dodecyl amine……………………………………………………… 38
3.1.7. Hexadecyl amine…………………………………………………… 38
3.1.8. Octadecyl amine……………………………………………………. 38
3.1.9. Dibenzoyl Peroxide (DBPO) ………………………………………. 38
3.1.10. Xylene…………………………………………………………….. 38
3.1.11. Isopropyl Alcohol…………………………………………………. 38
3.1.12. Methyl Alcohol……………………………………………………. 38
3.1.13. Ethyl Alcohol……………………………………………………… 38
3.1.14. Potasiumhydroxide (KOH) ………………………………………. 39
3.1.15 Hydrochloric Acid (HCl) ………………………………………….. 39
3.1.16. Sodiumcarbonate (Na2CO3. H2O ) ……………………………….. 39
3.1.17. Bromothymol Blue……………………………………………….. 39
3.1.18. Methylene Red……………………………………………………. 39
3.2. Equipment Used……………………….……………………………… 39
3.2.1. Magnetic Stirrer With Heater…………………………….………... 39
3.2.2. Vacuum Drying Oven…………………………..………………….. 39
V
3.2.3. Microwave Oven……………………….………………………….. 39
3.2.4. Extruder…………..………………………………………………… 40
3.2.5 XRD Analysis………………………………………………………. 41
3.2.6. Mechanical Test Device………………………….………………... 41
3.2.7. Shore-D Hardness Test Device…………………………………….. 41
3.2.8. Melt Flow Index device……………………..……………………… 41
3.3. Experimental Procedure………………………………………………... 43
3.3.1. Preparation and Purification of Grafted Polyolefins…………….… 43
3.3.2. Preparation of Organoclays……………………………….……….. 44
3.3.3. Preparation of PNC………………………………………………… 44
3.4. Tests and Analyses……………………………………………………. 45
3.4.1. Measurement of Grafting Ratio by Analytical Method……..……… 45
3.4.2. XRD Analysis……..……………………………………………….. 45
3.4.3. Mechanical Test……………………………………………..……… 45
3.4.4. Shore-D Hardness Test………………………………………..….. 46
3.4.5. Melt Flow Index Test……………………………..……………….. 46
4. RESULTS AND DISCUSSION…………………………………………... 47
4.1. The Optimization of Reaction Conditions……..…………………….. 47
4.2. Synthesis Conditions For Characterization of Samples…………..… 48
4.3 XRD Analysis Results…….…………………………………………… 48
4.4. Mechanical Characterization Test Results….………………………. 49
4.4.1. Tensile Tests Results…………………….…………………………. 49
4.4.2. Hardness Tests Results……………………..………………………. 50
4.3. Melt Flow Index Test Results……………………………………….. 50
5.CONCLUSION…………………………………………………………….. 52
REFERENCES………………………………………………………………. 54
APPENDIX…………………………………………………………………... 58
BIOGRAPHY………………………………………………………………... 73
VI
LIST OF TABLES
Table 2.1: The most commonly observed coordination plyhedra for the common elements in silicate structures…………………………..……………..…...
5
Table 2.2: Operating Conditions of LLDPE Processes……………............................. 14
Table 2.3: The relationship between density and the various properties of the polymers……………………………………………………………….........................
17
Table 2.4: Changes in polymer properties with melt index………………………….. 18
Table 2.5: Miciblity and immicibility of compatibilizers………….............................. 19
Table 3.1: Test concitions and standarts according sampe type……………………… 42
Table 3.2: Average MFI values with used weight usen in cylinder and measure time…………………………………………………………………………………….
42
Table 6.1: G.D. of LDPE with IA and monoesters and % grafting. ([DBPO]=0.75 g/100g LDPE, T=1400C, MW power=100 W)…………...………………..
57
Table 6.2: G.D. of LLDPE with IA and monoesters and % grafting. ([DBPO]=0.75 g/100g LLDPE, T=1400C, MW power=100 W)……..................................
57
Table 6.3: Sample descriptions and contents of samples which contain LDPE……… 57
Table 6.4: Sample description and contents of samples which contain LLDPE …….. 59
Table 6.5: XRD measurement results of LDPE containing samples ….……………... 60
Table 6.6: XRD Patterns of LLDPE containing samples…………………………… 62
Table 6.7: Mechanical measurements of LDPE including samples………………….. 63
Table 6.8: Mechanical measurements of LLDPE including samples………………… 64
Table 6.9: Shore-D measurement results of PNC samples…………………………… 65
Table 6.10: MFR, MVR, n-MFR and n-MVR values of all samples and control units………………..…………………………………………………….
66
VII
LIST OF FIGURES
Figure 2.1: Polyhedra and the corresponding atomic arrangement for the two principal polyhedra of silicate mineral structures……………………......
5
Figure 2.2: Shematic represantation of clay mineralstructure…………….................. 8
Figure 2.3: Structure of 2:1 phyllosilicates…………………………………………... 11
Figure 2.4: Molecules of LDPE, LLDPE and HDPE………………………………… 13
Figure 2.5: Schematic representation of an AB block copolymer compatibilizing a blend of polymers A and B…………………….………………………
20
Figure 2.6: Schematic representation of a compatibilization reaction ……………… 21
Figure 2.7: Method for creating intercalated polymer-clay architectures via direct polymer contact and via insitu polymerization ………………………….
25
Figure 2.8: Shematic representation of the various PNC architectures………………. 28
Figure 2.9: Wide-angle and small-angle X-ray diffraction of polymer samples…….. 30
Figure 3.1: HAAKE MiniLab Micro Compounder …………………………………. 40
Figure 3.2: Control panel of the MiniLab extruder...................................................... 40
Figure 3.3: Shore-D hardness measure device………………………………... 41
Figure 3.4: “Melt Flow Index” MFI device.................................................................. 42
Figure 3.5: Schematic representation of MFI device………………………………… 43
Figure 6.1: XRD pattern of Nanofil 757…………………………………................... 68
Figure 6.2: XRD patterns of polymer nanocomposite samples that contains LDPE as matrix and MMI in compatibility……….…………………………….
69
Figure 6.3: XRD patterns of polymer nanocomposite samples that contains LLDPE as matrix and MMI in compatibilizer……..…………………………….
70
Figure 6.4: XRD patterns of some polymer nanocomposite samples that contains LLDPE as matrix and IA in compatibility………………………………
71
VIII
LIST OF SYMBOLS
λ = Wavelength, nm
Å = Ionic Radius
θ = Diffraction angle
d001 = Layer distance
IX
ABBREVIATIONS
CEC Cation Exchange Capacity
PO Polyolefine
PE Polyethylene
PNC Polymer Nanocomposites
LDPE Low Density Polyethylene
LLDPE Lineer Low Density Polyethylene
IA Itacnic Acid
MMI Mono Methyl Itaconate
MBI Mono Buthyl Itaconate
DDA Dodecyl amine
HDA Hexadecyl amine
ODA Octadecyl amine
MFI Melt Flow Index
MVR Melt Volume Rate
MFR Melt Flow Rate
X
EFFECT OF THE POLYETHYLENE GRAFT COPOLYMER TO
STRUCTURES AND MECHANICAL PROPERTIES OF
POLYETHYLENE/CLAY NANOCOMPOSITES
SUMMARY
Polyolefins are the most widely used polymers. Preparation of PO-based polymer
nanocomposites (PNC) is more difficult than that of any polymer, which contains polar
groups in its backbone [1,2]. Since low-density polyethylene (LDPE) and linear low-
density polyethylene (LLDPE) are non polar polymers, homogeneous dispersion of polar
clay can not be realized due to lack of PE miscibility with it or with organically-
modified clay (organoclay) with the enhancement of the clay dispersion, the aspect ratio
of the particle increases and the reinforcement effect improve. Strong interaction
between a non-polar polymer and polar organoclay might be achieved with addition of a
compatibilizer [2,4-7]. During melt-blending olefinic oligomers with polar functionality
or PO grafted with polar group are intercalated into clay galleries, facilitating dispersion
of silicates into PO [6]. Itaconic acid (IA) and its monoesters can be grafted onto
polyolefins [8].
This study includes the effects of addition of polar groups containing compatibilizers
onto the final properties of the PNCs. In these PNCs, PEs were chosen as matrix and
organoclays and compatibilizers as additives. Polar group containing compatibilizer was
prepared by grafting of itaconic acid (IA) and its monoesters (mono methyl itaconate
and mono butyl itaconate) onto low-density polyethylene (LDPE) and linear low-density
polyethylene (LLDPE). The layered silicate was Na montmorillonite (MMT) and
organoclays were prepared by modification of MMT with surface active agents such as
dodecyl amine (DDA), hexadecyl amine (HDA), and octadecyl amine (ODA). PNC
materials will be synthesized by using different amounts of PEs, organoclays, and
compatibilizers in Mini Lab Extruder.
In this context, first of all, the compatibilizers were prepared at 140°C with 100 W
microwave input power for 10 minutes reaction period. Polyolefin was dissolved in
XI
xylene then was mixed together with dibenzoyl peroxide and the polar monomers in a
certain proportion. In all experiments, the weight ratio of xylene to polyolefins was
always 10/1.
The grafting ratios (GR) of were measured at standart analytical method. The
determined GRs values are: 11.2x10-4 mole IA/100 g LDPE, 22.3x10-4 mole MMI/100
g LDPE, and 20.0x10-4 mole MBI/100 g LDPE, 5.8x10-4 mole IA/100 g LLDPE,
12.4x10-4 mole MMI/100 g LLDPE, and 11.8x10-4 mole MBI/100 g LLDPE.
The samples were prepared by single step melt mixing. Thus, 5-wt% organoclay and
different concentration of compatibilizers (5, 10, or 15 –wt%) were mixed with PEs in
Mini Lab extruder at 177°C set temperature, 87 rpm screw speed with 2 min. cycling
time.
PNCs were examined by using the X-ray diffraction (XRD). The tensile 1% secant
modulus; strength, strain and toughness at maximum and at break were determined. The
processability of samples were investigated by melt flow measurements.
Each sample description refers to a specific composition involving the components used
in the preparation of the samples.
XRD results of the original clay, modified clays and the nanocomposites prepared are
provided in Table 1. X-Ray diffraction analyses were used to measure the separation of
original clay layers by modifying and dispersion of organoclay in polymer matrix. It was
observed that the compatibilizer content of 5 wt% does not effect the dispersion of
organoclay in matrix while compatibilizer content of ≥10 wt% significantly increases
the dispersion of the organoclay. The complete exfoliation was obtained for LDPE-IA-
XII
OHDA 5-C10, LDPE-IA-OHDA 5-C15 ,LDPE-MMI-OHDA 5-C 15 and LLDPE-IA-OODA 5-
C 15 samples.
Table 1: X-Ray diffraction analyses results of PNC samples
Tensile 1 % secant modulus, maximum strength, strength at break, strain at break, and
toughness (W) at break of nanocomposites were measured and calculated values are
listed in Table 2 and Table 3.
Maximum strength (σmax), strength at break, strain at break, and toughness at break (W)
of the NC increase with increasing compatibilizer content. Mechanical tests revealed
that increasing chain length of surface active modifying agent increases the dispersion of
montmorillonite layers in matrix. On the other hand, the type and percentage differences
XIII
of compatibilizers significiantly effect not only the dispersion of clay layers but also
mechanical properties of PNC.
Table 2. Mechanical measurements of the samples including LDPE
XIV
Table 3. Mechanical measurements of the samples including LLDPE
Compatibilizers might also influence the melt properties of the polymer matrix as
observed during the MFR measurements. Calculation of “normalized” MFR values helps
to see the interaction of clay with the continuous PO matrix.
XV
The results show that MFR data are able to provide an indication of exfoliation and
dispersion of clay in the PE matrix (Table 4). Increasing of n-MFR and n-MVR values
with increasing compatibilizer content showed that, processability of nanocomposites
was improved by addition of grafted PE compatibilizers.
Table 4. MFR, MVR, n-MFR and n-MVR values of PNC samples
Intercalated nanocomposites were prepared using functionalized PE as compatibilizers. It was
shown that clay dispersion depends on the type and concentration of grafted polar groups. Thus,
addition of 5-wt% compatibilizer was not effective. Using compatibilizer content higher than 5-
wt% can also increase all the mechanical properties. Increasing of n-MFR and n-MVR values
with increasing compatibilizer content in the nanocomposites resulted in the improved
processability of nanocomposites by addition of compatibilizers to the PNCs.
XVI
POLİETİLEN AŞI KOPOLİMERLERİNİN POLİETİLEN/KİL
NANOKOMPOZİTLERİNİN YAPISINA VE MEKANİK ÖZELLİKLERİNE
ETKİSİNİN İNCELENMESİ
ÖZET
Poliolefinler fiziksel ve mekaniksel özelliklerinin iyiliği, düşük maliyetlerde kolay
işlenebilirliği ve birçok uygulamada çok yönlü malzeme olarak kullanılabilmesinden
dolayı çokça tüketilebilen termoplastik polimerlerdir. Poliolefin tabanlı polimer
nanokompozitlerin hazırlanışı ana zincirinde polar grup taşıyan herhangi bir polimerin
hazırlanışından daha zordur.[1,2] Alçak yoğunluklu polietilen (AYPE) ve doğrusal
alçak yoğunluklu polietilen (DAYPE) polar polimerler olmadıklarından dolayı
polietilenin kendisiyle veya bir oganokille karışma kabiliyetinin olmamasından dolayı
polar killerle homojen dağılımı gerçekleşemez. Artan kil dağılımı katkı maddesinin
etkinliğini artırır.[5] polar olmayan polimer ve polar organokil arasındaki kuvvetli
etkileşim bir uyumlaştırıcının katılmasıyla sağlanabilir.[2,4-7] Polar fonksiyonelliği
olan olefinik oligomerler veya polar grupla aşılanmış poliolefinler eriyik karıştırması
sırasında silikatların poliolefinler içersine dispersiyonunu kolaylaştırarak kil galerileri
içine dağıtılımı sağlanır.[6] İtakonik asit ve monoesterleri poliolefinler üzerine
aşılanabilir.[8]
Bu çalışma polar grup içeren uyumlaştırıcıların eklenmesnin polimer
nanokompozitlerin nihai özellikleri üzerine etkisinin incelenmesini içermektedir. Bu
polimer nanokompozitler matris olarak polietilen, katkı olarak uyumlaştırıcı ve
organokil içerir. Polar gurup içeren bu uyumlaştırıcılar itakonik asit (IA) ve
monoesterlerinin (monometil itakonat ve mono butil itakonat) alçak yoğunluklu
polietilen (AYPE) ve doğrusal alçak yoğunluklu polietilen (DAYPE) üzerine
aşılanmasıyla elde edilmişlerdir. Organokiller, tabakalı silikat yapıdaki Na
montmorillonitin, yüzey aktif modifiye bileşenleri olan dodesil amin (DDA),
hekzadesil amin (HDA) ve oktadesil amin (ODA) ile modifikasyonundan elde
edilmiştir. Polimer nanokompozit malzemeler değişik miktarlarda polietilen,
organokil ve uyumlaştırıcının Mini Lab Ekstruderde işlenmesiyle elde edilmiştir.
XVII
Bu bağlamda, öncelikle uyumlaştırıcılar 140°C’ da, 100W mikrodalga boyunda, 10
dakika reaksiyon süresinde sentezlendi. Poliolefinler ksilen içersinde çözüldü ve
ardından dibenzoil peroksit (DBPO) ve belli oranlarda polar monomerler ile
karıştırıldı. Tüm deneylerde, ksilen ile poliolefin ağırlık oranı 1/10 olarak
kullanılmıştır. Aşılanma dereceleri (AD) standart analitik metotlarla ölçülmüştür.
Ölçülen aşılanma derecesi sonuçları: 11.2x10-4 mol IA/100 g AYPE, 22.3x10-4 mol
MMI/100 g AYPE, ve 20.0x10-4 mol MBI/100 g AYPE, 5.8x10-4 mol IA/100 g
DAYPE, 12.4x10-4 mol MMI/100 g DAYPE,ve 11.8x10-4 mol MBI/100 g DAYPE.
Örnekler tek basamaklı eriyik karıştırma yöntemiyle hazırlanmıştır. Bu nedenle, %5
organokiller ve değişik konsantrasyonlarda uyumlaştırıcılar (%5,10 ve 15) minilab
ekstruderde 177 °C proses sıcaklığında, 87 rpm vida hızında ve 2 dakika çevrim süresi
kullanılarak polietilenler ile karıştırılmıştır.
Polimer nanokompozitler X-Ray difraksiyonu (XRD) ile incelenmiştir. 1% sekant
modülü; Maksimum gerilim (σmax), kopma gerilimi, kopmada uzama ve tokluk (W)
değerleri mekanik tesler ile hesaplanmıştır. Örneklerin işlenebilirliği eriyik akış
ölçümleri ile irdelenmiştir.
Her örnek tanımlaması, örneklerin hazırlanılmasında kullanılan bileşenleri içerecek
şekilde yapılmıştır.
Ojinal kil, modifiye kil ve hazırlanılan nanokompozitlerin XRD sonuçları Tablo 1’de
verilmiştir. Orjinal kil tabakalarının modifikasyonla ayrılışını ve organokillerin
polimer matris içersinde dağılımını incelemek üzere X-Ray difraksiyon analizleri
yapıldı. %10’dan fazla olan uyumlaştırıcı yüzdesinin organokil dağılımını belirgin bir
şekilde arttırdığı gözlemlenirken, %5 uyumlaştırıcı yüzdesinin organokilin matris
içerisindeki dağılımını etkilemediği gözlemlendi. Kilin tam dağılımı AYPE-IA-OHDA
XVIII
5-C10, AYPE-IA-OHDA 5-C15 ,AYPE-MMI-OHDA 5-C 15 ve DAYPE-IA-OODA 5-C
15 örneklerinde elde edildi.
Tablo 1: Polimer nanokompozit örneklerinin X-Ray difraksiyon analiz sonuçları
Nanokompozitlerin, ölçülüp hesaplanan, 1% sekant modülü, maksimum gerilim
(σmax), kopma gerilimi, kopmada uzama ve tokluk (W) değerleri Talo 2 ve Tablo 3
de verilmiştir.
Maksimum gerilim (σmax), kopma gerilimi, kopmada uzama ve tokluk (W)
uyumlaştırıcı miktarının artmasıyla arttığını gözlemledik. Mekanik testler, yüzey aktif
maddenin zincir uzunluğunun artmasıyla matris içersindeki montmorillonit
tabakalarının dağılımının arttığını göstermektedir. Diğer yandan uyumlaştırıcı tipi ve
yüzdesi sadece kil tabakalarının dağılımını etkilemekle kalmayıp mekanik özellikleri
de değiştirmektedir.
XIX
Tablo 2. Polimer matris olarak AYPE içeren örneklerin mekanik ölçümleri.
XX
Tablo 3. Polimer matris olarak DAYPE içeren örneklerin mekanik ölçümleri.
Uyumlaştırıcı, eriyik akış ölçümlerinde görüldüğü üzere polimer matrisin eriyik
özelliklerini etkilemektedir. Normalize eriyik akış indeksinin hesaplanması kil ile
polimer matris arasındaki etkileşimin irdelenmesine yardımcı olmuştur.
XXI
Sonuçlar göstermiştir ki; n-MFR ve n-MVR değerlerinin uyumlaştırıcı yüzdesiyle
artması nanokompozitlerin işlenebilirliğinin aşılanmış polietilen uyumlaştırıcılarının
ilave edilmesiyle artmaktadır.(Tablo 4)
Tablo 4. Örneklerin n-MFR ve n-MVR sonuçları.
Fonksiyonelize polietilen kullanılarak interclate nanokompozitler hazırlanılmıştır. Kil
dağılımının aşılanmış polar grupların konsantrasyonuna ve tipine bağlı olduğu
gösterilmiştir. %5 uyumlaştırıcı eklenmesinin etkili olmadığı görülmüştür. %5 den
fazla uyumlaştırıcı kullanıldığında tüm mekanik özellikler artmaktadır. n-MFR ve n-
MVR değerlerinin artan uyumlaştırıcı miktarlarına paralel olarak arttığı
nanokompozitlerde, polimer nanokompozitlerin işlenebilirliğinin uyumlaştırıcı
yüzdesindeki artışla arttığı saptanmıştır.
1
1. INTRODUCTION
Polymers have become one of the most important materials in our daily life.
Increasing demand for using them forced the scientists to improve their properties.
Therefore, in recent years, inorganic nanoparticle filled polymer composites have
received increasing research interest, mainly due to their ability to improve
properties of polymers.
In general, when composites are formed two or more physically and chemically
distinct phases (usually polymer matrix and reinforcing element) are joined and the
properties of the resulting product differ from and are superior to those of the
individual components. The structures and properties of the composite materials are
greatly influenced by the component phase morphologies and interfacial properties.
Nanocomposites are based on the same principle and are formed when phase mixing
occurs at a nanometer dimensional scale. As a result, nanocomposites show superior
properties over their micro counterparts or conventionally filled polymers. Polymer
nanocomposites are a class of reinforced polymers with low quantities of
nanometric sized clay particles (generally), which give them improved properties.
The reinforcing effect of nanoparticles is related to the aspect ratio (p) (ratio of the
length or thickness to that of the diameter) and the particle-matrix interactions.
Independent of the actual dimensions, for p > 500 the reinforcing effects are the
same as those of any infinitely large particles. Because of the small size, the
nanoparticles are invisible to the naked eye, so nanocomposite are transparent.
Polyolefins (PO) are the most widely used polymers in preparation of polymer
nanocomposites (PNC) and it is more difficult than that of any polymer, which
contains polar groups in its backbone [1,2]. Since low-density polyethylene (LDPE)
and linear low-density polyethylene (LLDPE) are non polar polymers, homogeneous
dispersion of polar clay can not be realized due to lack of PE miscibility with it or
with organically-modified clay (organoclay) with the enhancement of the clay
dispersion, the aspect ratio of the particle increases and the reinforcement effect
improves. Strong interaction between a non-polar polymer and polar organoclay
might be achieved with addition of a compatibilizer [2,4-7]. During melt-blending
olefinic oligomers with polar functionality or PO grafted with polar group are
2
intercalated into clay galleries, facilitating dispersion of silicates into PO. Itaconic
acid (IA) and its monoesters and they can be grafted onto PO [8].
Homogeneous dispersion of nano-sized fillers in the matrix provides a large
interfacial area; otherwise the loosely agglomerated nanoparticles would easily
result in failure of the composites when they are subjected to force. A homogeneous
product, incorporation of any additives requires a serious mixing in molten state,
which is primarily provided by melt blending process by means of extrusion.
In this study, nanocomposites were produced by means of a corotating twin screw
extruder in single step melt mixing method. This study was carried out to determine
the effects of compatibilizer on the properties of PE-based PNC. In order to prepare
the compatibilizers, LDPE and LLDPE were grafted with itaconic acid (IA),
monomethyl itaconate (MMI) and monobutyl itaconate (MBI) by in a microwave
assisting system. Organically modified Na-MMT was used as the nanofiller.
Modifications of clays were done by using alkyl ammonium salts as the surface
active modification agents (dodecyl amine (DDA), hexadecyl amine (HDA) and
octadecyl amine (ODA)).
Dispersion of clay was characterized by using XRD tests, mechanical
characterization of the samples was done with stress-strain measurements data, and
the processabilities of PNCs were investigated by MFI measurements techniques.
3
2. THEORETICAL PART
In general, a composite is defined as two or more components differing in form or
composition on a macroscale, with two or more distinct phases having recognisable
interfaces between them. Nanocomposites (NCs) are materials that comprise a
dispersion of nano meter (10-9) size particles in a single or multicomponent matrix. [1]
The matrix may be metallic, ceramic or polymeric. Depending on the matrix nature
NCs may be assigned into these three categories. The nano particles are classified as; 1)
lamellar, 2) fibrillar, 3) tubular, 4) spherical, and 5) others. For the enhancement of
mechanical and barrier properties of NCs lamellar particles are preferred. For rigidity
and strength enhancement, fibrillar, for optical and electrical conductivity enhancement,
spherical or other particles have been used. In polymer nanocomposites (PNC), matrix
is a single or multicomponent polymer. In this work, LDPE and LLDPE with their
grafted copolymers were used as multi component matrix and the organoclays as nano
particle additives. To understand the PNC structure these main components will be
discussed: clay minerals and polymer matrices.
2.1. Clay Minerals
The terms "clay" and "clay mineral" are used in various subjects. A common
explanation of a clay substance is a material whose particles are very small. This is
general engineering usage. The term "clay" now refers to any material which exhibits a
plastic behavior when mixed with water, while "clay mineral" refers to materials which
have a layer structure. Clay minerals typically form at low temperatures, at low
pressures in the presence of much water, in nature. Under these conditions, perfection in
the organization of the crystal structure is unlikely. The details of the crystal structure
of these materials are of great importance in understanding the physical and chemical
properties of clays. This also is true of the highly disordered or amorphous materials
where there still exists short range order.
4
2.1.1. Silicate Mineral Structures
Silicate minerals are oxides of silicon and a small number of elements from the first
three columns of the periodic table and the transition elements. As such they closely
mirror the most of the elements in the crust of the Earth (Table 2.1). Since the number
of different elements which play a major role in the structure of silicate minerals is
small, it is not surprising that the fundamental building blocks of these minerals, and
many other non-silicate minerals, are few. The basic building blocks are simple platonic
polyhedra, largely tetrahedra and octahedra, which represent the placement of oxygen
atoms and the smaller cations. The number of oxygen atoms arranged about a cation is
termed the coordination number (CN); the smaller the cation, the smaller the CN.
Figure 2.1 shows a tetrahedron and an octahedron in both aspects, i.e., as a polyhedron
and as the arrangements of oxygen coordinating the central cation.
While these drawings show perfect polyhedra, in real mineral structures, these are
rarely perfectly regular. For example, that the edges of the polyhedra are almost always
of slightly different lengths and the central cation may be displaced from the geometric
center. For the purposes of this discussion such deviations are not important. Such a
view of crystal structures leads to a simplistic but nonetheless very useful concept of a
silicate mineral, that is, a mineral is an arrangement of boxes in space (the coordination
polyhedra), and we construct such a mineral by filling the boxes with appropriate
cations.
In a simple structure there might be only two kinds of boxes, representing tetrahedra
and octahedra, appropriately linked together. Thus, we can change the chemical
composition of a mineral by replacing all or part of the cations in one type of box by
another kind of cation, such that size and valence considerations are not violated. Two
divalent cations which are not very different in ionic radius, magnesium and iron, for
example, can readily substitute for each other in an octahedral site.[9]
5
Table 2.1: The most commonly observed coordination polyhedra for the common elements in silicate structures in order of decreasing amount in the Earth’s crust, omiting which is the most abundant element.
Element C.N. Polyhedron Ionic Charge Ionic Radius (Å)
Slicon 4 Tetrahedron +4 0,26
Aluminum 4
6
Tetrahedron
Tetrahedron
+3
+3
0,39
0,54
Iron 6
6
Octahedron
Octahedron
+2
+3
0,78
0,65
Calcium 6
8 Octahedron cube
+2
+2
1,00
1,12
Sodium 6
8 Octahedron cube
+1
+1
1,02
1,10
Pottasium 6
8 Octahedron cube
+1
+1
1,38
1,51
Magnesium 6
8 Octahedron cube
+2
+2
0,72
0,89
Figure 2.1: Polyhedra and the corresponding atomic arrangement for the two principal polyhedra of silicate mineral structures, i.e. octahedra (left) and tetrahedra (right). [9]
2.1.2. Classification of Clay Minerals
There are 4 types of clay minerals which are classified by their chemical formula;
Caolinite, Smectide, Illite and Clorite.
6
2.1.2.1. Caolinit group
This group contains caolinit, dicit and nacrit. The general formula of the caolinit group
is Al2O3·2SiO2·2H2O. There is no pure caolinit source in nature and generally they
contain iron oxide, silica, silica types components. They are used as filler in ceramics
paint, plastics and rubber and they are widely used in paper industry to product bright
paper.
2.1.2.2. Illit group
These groups differ from smectite group clays by including potassium and can called as
mica group. They are water included microscobic muscovit minerals and they are
formation minerals which can be seperated to layers. The general formula of illit group
is (K, H) Al2 (Si, Al)4 O10 (OH)2·xH2O. The stucture of this group is the same with
slicate layered montmorillonite group. It can be used as filler material and in driling
mud.
2.1.2.3. Clorit group
Clorit group clays have slim grain structure and green colour. This group clay includes
a great deal of magnesium, Fe (II), Fe (III) and alumina. Clorit group minerals are
generally known as fillosilicate group and they are not acceppted as one of clay group.
This group has got a lot of members like amesite, nimite, dafnite, panantite and
peninite. General formula of Clorit group is X4·6 Y4O10 (OH, O)8. In this formula, X
shows Al, Fe, Li, Mg, Mn, Ni, Zn and rarely Cr elements, and Y shows Al, Si, B, Fe
elements. They are not used in industry.[10,11]
2.1.2.4. Smectite group
The smectite minerals are classified according to the nature of the octahedral sheet
(dioctahedral versus trioctahedral), by the chemistry of the layer and by the site of the
charge (tetrahedral versus octahedral). The smectite minerals are very complex group,
frequently having both octahedral and tetrahedral substitutions each contributing to the
overall layer charge. The following formula are based on a layer of 0.33, with the value
varying between approximately 0.2 and 0.6 and sodium is indicated as the interlayer
7
cation. There are three important dioctahedral smectites; two are aluminous and the
third is iron rich. With a predominantly octahedral charge, the mineral is
montmorillonite, Na0.33nH2O(Al1.67Mg0.33)Si4O10(OH)2 where, as before, the n indicates
a variable amount of interlayer water coordinating (or not) the interlayer cation. The
interlayer cation needs not be sodium, but this is the common occurrence. The term
"montmorillonite" was frequently used as a group name for any swelling 2:1 clay
mineral as well as the name of a specific mineral, clearly not a good situation. Presently
smectite is the group name and montmorillonite is restricted to a mineral name
belonging to that group. If the charge is predominantly tetrahedral and aluminous the
mineral is beidellite with an ideal composition of Na0.33nH2O Al2(Al0.33Si3.67)O10(OH)2.
Finally, if ferric iron substitutes for aluminum in the octahedral sites and the charge is
tetrahedral, one has montmorillonite, Na0.33nH2O Fe2(Al0.33Si3.67)O10(OH)2. The
trioctahedral equivalent of montmorillonite is the mineral hectorite, ideally Na0.33nH2O
Mg3(Al0.33Si3.67)O10(OH)2. It should be noted that in contrast to montmorillonite,
hectorites have lithium (1+) in some octahedral sites (not shown in the above formula)
adding to the total layer charge. For saponite, aluminum substitutes for magnesium in
the octahedral sites generating a positive contribution to the layer charge which reduces
the negative contribution from the tetrahedral sites. The ideal formula without the
aluminum substitution is Na0.33nH2O Mg3(Al0.33Si3.67)O10(OH)2. The interactions
between adjacent smectite layers are not very strong and the interlayer material,
hydrated cations, water, organics, are disordered, so that there is little coherence from
one layer to the next. As a consequence, it is normally not possible to speak of a crystal
of a smectite. There are some exceptions, saponite being one, where there is a greater
degree of stacking regularity; it shows a degree of disorder. [9]
Montmorillonite is the mineral with the general formula of Na0,2 Ca0,1 Al2 Si4 O10 (OH)2
(H2O)10. Montmorillonite is a fine powder which has monoclinic-pyrismatic crystal
structure, a colour from white to brown-green and yellow, average density of
2.35 g/cm3, molecular weight of 549.07 g/mol and hardness of 1.5–2 (Figure 2.2).
Single montmorillonite crystals are quite fine, granulated and they got random outher
lines. In general a montmorillonite crystal consists of 15–20 silicate units. This property
8
is so usefull for engineering projects. There are two different swelling types of
montmorillonite according to expansion size of the basal space as crystallized and
osmotic swelling. Crystillized swelling occurs when the water molecules enter in to the
unit layers. First layer of the water molecules which are adsorbed occurs when they
bind with hydrogen bonds to hexagonal oxygen atoms. Montmorillonitles whose
cations are exchangable hydrates as Na+, Li+ can swell to 30–40 Å. Moreover,
sometimes this swelling level increases up to hundred. This type ditance is called as
osmotic swelling. Montmorillonits do not swell much when they got high valanced
cations as exchangable cations.[12-16]
Figure 2.2: Shematic represantation of 2:1 clay mineral structure (red Al, small ones O, light violet Ca, light purple Si).
The reason of this sittuation is that gravitational forces between silicate and cation
layers are higher than ion hidration thurst force [17]. Montmorillonites enable polar or
ionic organic molecules to penetrate between the layers. Adsorption of organical
9
mixtures causes to formation of organo-complex montmorillonites. Penetrating of big
molecules in to layers of clay mineral could be determined by using XRD
measurements. Montmorillonits have 2:1 type layered structure. Crystal like structure of
the montmorillonite occures from, silicon-oxygen (Si-O) tetrahedral layer with (Al-O-
OH) oktahedral layer which is between two Si-O layers. Silicon atoms are bonded with
4 oxygen atoms in (Si-O) layers. Oxygen atoms are placed regularly as one in centre of
silicon atom and the other 4 atoms are on the corners of the tetrahedron (Figure 2.3).
Layers are divided between every thirth neighbour tehrahedral layer structure from 4
oxygen atoms of tetrahedron layer. All of the fourth oxygen atom of the tetrahedron has
condition as oriented to lower side of structure which can be seen in Figure 2.4 and
they are at the same plane with the -OH groups of alumina octahedral layers. [18,19]
Figure 2.3: Structure of 2:1 phyllosilicates.
2.1.3. Cation Exchange Capacity
Clay minerals get ability of pulling some ions and push them back again. In this case
ions could replace each other. In the tetrahedron layer of montmorilonite Si+4 with Al+3
and in the octahedron layer of montmorilonite Al+3 with Mg+2, Fe+2, Zn+2 and Li+1 can
10
replace with each other. In tetrahedron this cation exchange capacity is low, despite of
this it is significiantly high in octahedron. At the end of cation exchange, positive and
negative charges occure. Two layered clays have natural surfaces according to their
electrical charges but three layered clays have charged surfaces. Positive charge
deficiency can be overcome by bonding of Na+, K+, Li+ or Ca+2 ions to crystal cage
from their water layer of unit area.[12]
Despite of these conditions units can give these cations back, naturally. The ions
captured by clay minerals in exchangable position are called as “exchangable ions”.
Because these ions are mostly cations and their ion exchange ability or cation echange
capacity is higher then certain values, these ions show properties such as clay minerals
grade of swelling, gelation etc. Cation exhange capacity is defined as (meq.) Na2O in
100 gr clay. This charge is not locally constant, but varies from layer to layer, and must
be considered as an average value over the whole crystal. Layered silicates have two
types of structure: tetrahedrally substituted and octahedrally substituted. In the case of
tetrahedrally substituted layered silicates, the negative charge is located on the surface
of silicate layers and, hence, the polymer matrices can interact more readily with these
than with octahedrally substituted material. The exchangable cations in clay minerals
are H+, Na+, K+, Ca+2 and Mg+2. The exworks shows us cation exchange capacity of
montmorillonite is between 80–150 meq.[10]
The general cation exchange capacity of natural or synthetic clay minerals is between
50–200 meq/100 gr. Because of the cation exchange capacity is higher than 200, the
forces between layers prevent seperation of clay layers. On the other hand, clay
minerals, which cation exchange capacity lower from 50 meq/100 gr clay, could not
seperate the clay layers. Due to these reasons, montmorillonite which cation exchange
capacity between 50–150 meq/100 g clay, are used as swelling agent in NCs.[12]
2.1.4. Inter Layer Formation
Several phyllosilicate minerals, either naturally or as the result of chemical treatment,
have molecular species inserted between the silicate layers. Water is the most common
interlayer species in nature, and water is normally found in smectites, vermiculites and
11
hydrated halloysites. The quantity of interlayer water is a function of relative humidity
and the type of interlayer cation, in the case of smectites and vermiculites. There is a
great interest in the nature of the interface between water and silicate minerals. Much of
the chemical activity in soils, sediments and porous rocks occurs at such an interface.
Experimentally, it is very difficult to examine this interface because it is such a small
part of the liquid-solid system. Hydrated smectites and vermiculites have water between
all of the silicate layers and therefore the percentage of the sample which is interface is
enormously larger than the interface between a grain of quartz in contact and liquid
water. Another way to look at this is that the surface are of a quartz sand is probably
much less than 1 m2/gram while a typical smectite has a surface area of as much as 800
m2/gram.[9]
The surfaces of clay minerals present a number of potential sites at which organic
molecules could attach themselves. These sites include the exchangeable cations. The
oxygen atoms can occupy the surface of the silicate layer and at the edge of these
layers. On the other hand, hydrogen atoms take part of surface hydroxyl groups. So
there is a wide variety of interaction possible between the heterogeneous clay surface
and the different functionalities of organic materials. If any organic material existing on
external particle surfaces, intercalation of layers can occur.[9]
One can categorize the types of organic-clay interactions based on the bonding
mechanisms between the organic and the clay surface/inter layer (inorganic) cations.
• Cationic bonding: These involve organic cations such as the alkyl ammonium cations
or amines and carbonyl groups which have become protonated, depending on the pH.
• Ion-dipole and coordination bonding: This is particularly common for organic
molecules having a permanent dipole, e.g., acetone.
• Hydrogen bonding: The organic molecule can be either the donor or the acceptor or
both, depending on the nature of the clay surface and the organic molecule.
• Tetrahedral tetrahedral (TT) bonding: Molecules such as benzene can interact via their
valance electrons with, for example, Cu2+ interlayer cations. Hydrogen bonding and TT
bonding are both examples of Lewis electrondonor/ electron-acceptor interactions.
12
2.2. Polyolefins
A polyolefin, whose equivalent term is polyalkene, is a polymer produced from a
simple olefin (also called an alkene) as a monomer. Their main members are
polyethylenes and polypropylenes. Industrial production of polyolefins cover low
density polyethylene (LDPE), high density polyethylene (HDPE), polypropylene (i-PP),
and together with some copolymers. [22-24]
2.2.1. Polyethylenes
Polyethylene is classified into several different categories based mostly on its density
and branching (Figure 2.4). The mechanical properties of PE depend significantly on
variables such as the extent and the type of branching, the percent crystalinity, and the
molecular weight.
The types of polyethylene mostly consumed are LDPE (low density PE), LLDPE
(linear low density PE), HDPE (high density PE), HMWPE (high molecular weight
poly ethylene), UHMWPE (ultra high molecular weight polyethylene), HDXLPE (high
density cross-linked PE), PEX (cross-linked PE), MDPE (medium density PE), and
VLDPE (very low density PE).
2.2.1.1. Low Density Polyethylene (LDPE)
LDPE is defined by a density range of 0.910 - 0.940 g/cm3. LDPE has a high degree of
short and long chain branching, which means that the chains do not pack into the crystal
structure as well. This results in a lower tensile strength and increased ductility. LDPE
is created by free radical polymerization. The high degree of branches with long chains
gives molten LDPE unique and desirable flow properties. LDPE is used for both rigid
containers and plastic film applications such as plastic bags and film wrap.[28]
LDPE is produced by a free-radical initiated reaction using oxygen or other free radical
initiators such as organic peroxides or azo compounds. Synthesis conditions are usually
250–300 °C outlet temperature, 3000 atm. pressure. Nominal reactor residence times
are about 10–50 seconds.
13
Figure 2.4: Molecules of LDPE, LLDPE and HDPE
Heat of polymerization is about 800 KCal/gm, which must be removed during the short
residence time available. Only a small part of this heat can be removed through the
reactor walls because of their comparatively limited area and necessary thickness. In
addition, the polymer tends to deposit on cool surfaces. In practice, heat is removed by
recirculating excess cool monomer and the system operates essentially adiabatically.
Therefore, production rates vary directly with the ethylene recirculation rate and the
allowable temperature rises through the reactor. Heat balance limits conversion to 15–
20% on each pass. Reactors are of two general types, autoclaves and high pressure
tubes. Each of these types produces slightly different polymers, primarily because of
differing temperature profiles through the reactors. [25-27]
2.2.1.2. Linear Low Density Polyethylene (LLDPE)
LLDPE is defined by a density range of 0.915 - 0.925 g/cm3 is a substantially linear
polymer, with 4-6 carbon containing short branches (short-chain alpha-olefins) with
approximately, every 100 carbons on the main chain. LLDPE has higher tensile
strength, higher impact and puncture resistance than LDPE. Lower thickness films can
be blown compared to LDPE, with better environmental stress cracking resistance
compared to LDPE but is not easy to process in packaging. Cable covering, toys, lids,
buckets and containers, pipe are some of the products can be made by LDPE. While
LDPE
HDPE
LLDPE
14
other applications are available, LLDPE is used predominantly in film applications due
to its toughness, flexibility, and relative transparency.[22,23]
Linear low density polyethylenes are made with transition metals catalysts/initiator
under 100-130 °C and up to 20 atm.(Table 2.2) Butene-1 is the usual comonomer, but
either hexene-1, octene-1, or 4 methylpenetene-1 is employed to give enhanced
physical and optical properties with higher production cost.
Table 2.2: Operating Conditions of LLDPE Processes
Conditions Slurry Fluidized
Temperature 80-120 80-120
Pressure (Mpa) 4-7 2-3
Residence Time (hours) 0,75-1,05 4-7
Convension/pass (%) 95 1-4
2.2.1.3. Other Polyolefins
i-PP and HDPE which are stereospecific polymers can be produced under the same
method given above for LLDPE. In the slurry process, MgCl2 supported TiCl4 is used as
catalyst and Al(C2H5)3 as co-catalyst in the n-heptane solution for both production,
generally. Atactic PP (a-PP) is the by-product of i-PP production.
2.2.2. Properties of Polyolefins
In today's competitive market place, prime grade commercial polyethylenes must be
both processable and uniform. We use the term “processability” to describe the ease or
difficulty with which an olefin can be handled during its fabrication into film, molded
items, pipe, etc. Polyethylene with good processability is one which possesses the
properties necessary to make it easy to convert the polyethylene pellets or powders into
the desired products. The main characteristics or properties which determine an olefin's
processability are molecular structure, uniformity, and additive content. However,
processability is a property which is a result of the basic properties mentioned above.
These characteristics include hot-melt extensibility, sensitivity to pressure and
15
temperature, smoking and odor, product stability during withdraw, and flow rate (which
is an operating condition). Uniformity is a characteristic of critical importance. It is
obtained only through rigorously controlled synthesis, densification, stabilization,
blending, and handling, so that lot-to-lot variation is minimized. The customers expect
to be able to process polymers during extended runs with, at worst, minor adjustments
to their machinery between lots of material. It’s also expected a polymer to be free of
contamination, dirt, discolored material, and other foreign matter and to be of light,
uniform color, unless pigmented. Polyethylene must also be uniformly granulated to
flow through the customers' handling and feeding systems. This means accurate and
uniform pellet size with freedom from excessive fines or oversize particles, and no
strings of agglomerated pellets or streamers. The polymer must also be free of excessive
moisture.
The main structural factors that determine PE properties are the degree of short and of
long chain branching, the average MW and the polydispersity. One of the most
important characteristics that determine in the highest degree the properties and the
behavior of different grades of PE is their branching. Branches prevent the polymer
chains from packing together regularly and closely and have a predominant effect on
the density of PE. The density can be considered a first indication of the degree of
branching: the lower the density the higher the degree of branching. The presence of
branches interferes with the ability of the polymer to crystallize. The degree of
crystallinity of LDPE is usually of the order of 55-70% compared with that of HDPE
which is 75-90%.
Other properties depending on crystallinity, such as stiffness, hardness, tear strength,
yield point, Young’s modulus in tension and chemical resistance, increase with
increasing degree of crystallinity (HDPE) whereas permeability to liquids and gases,
flexibility and toughness decrease under the same conditions
Since PE is crystalline nonpolar hydrocarbon polymer it has no solvents at room
temperature and dissolution takes place only on heating in solvents of similar solubility
parameter such as hydrocarbons and halogenated hydrocarbons. The higher the degree
16
of crystallinity results the higher the dissolution temperature. LDPE dissolves at 60°C
compared to 80-90°C for high density, more crystalline polymers.
The effect of branching also depends on the size of side chain branches. While short
branches have a predominant influence on the degree of crystallinity and therefore on
the density of the polymer, long branches affect more pronouncedly the polydispersity.
The side chains may be as long as the main chain and like it may have a wide
distribution of lengths. The higher the MW of the resulting polymer the wider the
MWD, as chain transfer reactions may occur as well on side chains. Such a polymer
may be made up of short chains grafted onto short chains, long chains onto long chains
and a vast range of intermediate cases. Long chain branches also affect the flow
properties. Long branched molecules are more compact and tend to entangle less with
other molecules resulting in lower solution and melt viscosities as compared with
unbranched polymers.[29,30]
2.2.2.1. Mechanical Properties of Polyolefins
Another factor that influences the properties of the melt, as well as those properties that
involve large deformations, is the weight-average MW. Ultimate tensile strength, tear
strength, low temperature toughness, softening temperature, impact strength and
environmental stress cracking increase as the MW increases; on the contrary, the
fluidity of the melt and the coefficient of friction decrease.
2.2.2.2. Dielectric
The electrical insulating properties of polyethylenes are excellent. The dielectric con-
stant increases linearly with increasing density. As it is a non-polar material, dielectric
constant and the power factor are almost independent of temperature and frequency.
2.2.2.3. Density
Polymer density is a rough measure of crystallinity and, therefore, of the physical and
optical properties that are dependent on the degree of crystallinity. The relationship
between density and the various properties of the polymers is illustrated in Table 2.3
LDPEs and LLDPEs of the same density have somewhat dissimilar properties. This
17
difference is largely because LDPE, being free radical initiated, contains a range of both
long and short side chains attached to the main polymer backbone.
Table 2.3: The relationship between density and the various properties of the polymers.
LLDPE, on the other hand, contains only short branch lengths, those of the comonomer.
Although the degree of crystallization is nearly the same, the morphology of the crystal
is dissimilar. LLDPE possesses many improved solid properties, such as strength,
toughness, and draw-down, but LDPE in general is easier to process, is softer, and
yields films with better optical properties.[28-30]
2.2.2.4. Melt Flow Index
The melt index (MI) is a rough measure of average molecular weight and melt
viscosity. It indicates how readily molten polymer will flow in processing machinery.
18
Table 2.4: Changes in polymer properties with melt index.
Because the melt index is measured at a single temperature at low shear, and because
melt viscosities are highly non-Newtonian, the melt index alone does not adequately
predict how processable a given polymer will be under higher shear conditions in
commercial processing equipment. However, the melt index is often an adequate
discriminant within a given group of resins produced under substantially similar
19
conditions. The various physical properties of the polymers will generally vary as the
melt index varies, as illustrated in Table 2.4.
2.3. Compatibilizer
Polymeric compatibilizers serve as their name indicates to make compatible the
different kinds of materials such as multi component structures. Before discussing the
compatibilization of polymer pairs in multi component structures, the compatibility of
polymer blends and the compatibilizers will be described.
2.3.1. Compatibility and Compatibilizers
When blending two polymers, the resulting behavior falls into three categories (Table
2.5). Either they are miscible and compatible or immiscible and incompatible, or they
behave somewhere in between these two extremes.
Table 2.5: Misciblity and immiscibility of compatibilizers.
20
The requirements are similar polarity and structure, and the result is a single-phase
mixture. The materials have different polarities and structures, and the result is a two-
phase mixture with poor properties, an undesirable state.
Rarer still is immiscibility and compatibility at which a mixture's constituents have
different properties, but show some interaction, because of reactive groups, surface
active agents, or compatibilizers.
Immiscibility and compatibility are not necessarily bad. Actually, the entire technology
of toughened polymers is based on this approach, because it synergistically combines
the properties of completely different polymers to form a blend with properties superior
to those of the individual blend components.[34,35] The theoretical explanation for why
such cases are observed has been extensively treated in the literature.[36]
Figure 2.5: Schematic representation of an AB block copolymer compatibilizing a blend of polymers A and B.
Compatibilizers that compatibilize two polymers, A and B, consist of two parts
(Figure 2.5). One part interacts with polymer A and the other part with polymer B, but
to do so effectively, they must be concentrated at the interface between the two
polymers.
The result is a better dispersion of the polymer blend as shown in Figure 2.6. Infinite
dispersion, however, is not necessarily desirable since a minimum particle diameter
exists for each system below which there will be no synergistic improvement in
properties (e.g., fracture toughness)
21
Figure 2.6: Schematic representation of a compatibilization reaction
2.3.2. Classification According to Properties of Compatibilizers
Compatibilizers can be classified as follows: non-reactive, reactive compatibilizers, and
random, graft, and block copolymers.
Non-reactive compatibilizers, which compatibilize two polymers, A and B, consist of
two parts: the first is soluble in polymer A, and the second is soluble in polymer B. The
compatibilizer's effect is derived from their solubility. Therefore, the solubility
parameters of both parts should be as close as possible to the solubility parameters of
the polymer components in the polymer mixture.[37-39]
A block copolymer contains blocks of the polymer pairs. These blocks can be reactive
or non-reactive polymers.[40]
In random copolymers, the components, the base polymer B and a comonomer A, are
distributed randomly along the polymer chain. Random copolymers are usually
produced in a high-pressure radical polymerization process.[41,42] Random
copolymers only work well as compatibilizers when the comonomer A is reactive.
In graft copolymers, either monomers or polymers are grafted onto each other. If only
monomers are grafted to the backbone, the monomer should be reactive. An example is
PP grafted with maleic anhydride. The exposure of the reactive monomers on the
usually non-reactive base polymer backbone makes them more accessible to an attack
by other polymers, transforming them into effective compatibilizers.
22
2.3.3. Works on IA/MMI/MAH Grafting Polyolefins in Recent Years
S.S.Pesetskii and his coworkers investigated grafting of itaconic acid on low density
polyethylene in molten state via reactive extrusion many times in recently years.
Pesetskii investigated firstly, initiator and stabilizator efficiency on grafting degree of
LDPE with IA. It was shown that initiator solubility affects the grafting degree. The
initiators which can be dissolve easily in LDPE, increases the grafting efficiency and
the closer the thermodynamic affinity between the peroxide and the monomer, and
decreases efficiency of grafting. The stabilizers (e.g.,1,4-dihydroxybenzene) with
increased affinity toward the monomer reduce the grafting yield and inhibit
crosslinking.[43,44] In another work, it was shown that thermomechanical and
rheological properties of LDPE was changed. According to results, while unmodified
PE exhibits two glass transition temperatures, modified PE with IA exhibits three glass
transition temperatures and with increasing of grafting degree melting temperature
increases 1-2 0C and melt flow rate (MFR) values decrease, it means that viscosity of
polymer increases.[45] Pesetskii worked on thermal and photo oxidation of grafted
LDPE and the functionalization of LDPE by grafting of itaconic acid to the
macromolecules was found to accelerate its thermal and photo-oxidation in water.[46]
Pesetskii made his last IA-g-LDPE work in presence of neutralizing agents. When the
grafting takes place in the presence of neutralizing agents, the efficiency of the itaconic
acid grafting onto macromolecules is found to increase. Neutralization of the grafted
itaconic acid contributes to an increase in the mechanical and impact strengths of blends
composed of functionalized low-density polyethylene and polyamide-6.[47]
M. Yazdani and his coworkers worked with monoesters of IA for grafting of PE and
PP. Firstly, to improve the compatibility and properties of blends based on high-density
polyethylene (HDPE) and the ethylene-propylene copolymer (EPR), the
functionalization of both through grafting with an itaconic acid derivative, monomethyl
itaconate (MMI), was investigated. The results show that the grafting reaction increases
the toughness and elongation at break of all tested blends and they retained their
strength and stiffness. Moreover, the grafted polymers behaved as nucleating agents,
accelerating the HDPE crystallization.[48] In another work, Yazdani synthesized
23
functionalized polypropylene by radical melt grafting either with monomethyl itaconate
and dimethyl itaconate to improve its compability of PP with PET. The use of PP
grafted with MMI as compatibilizer resulted in even a better dispersion of PP as the
minor phase increasing the components interface and there after to an improvement of
the adhesion between the two phases. The noncompatibilized blend in this case also
showed an even more pronounced two phase behavior as compared with PP/PET
blends. The impact resistance of PET in noncompatibilized blend was hardly affected
by incorporation of PP. However, when functionalized PP with either MMI or DMI was
used as blend compatibilizers, there was an increase of the impact resistance of PET.
This probably is due to spesific interactions and/or chemical reaction
(transesterification) between the functional groups of the compatibilizer with the blend
constituents resulting in a finer dispersion of the minor phase leading to improved
interfacial adhesion.[49]
The first grafting reaction of LDPE in a solution medium was worked by Yu-Zhong
Wang in recently year. The grafting reactions of MAH were carried out in microwave
assisting system. The reaction of maleic anhydride (MAH) grafted onto low density
polyethylene (LDPE) in xylene solvents in the presence of benzoyl peroxide (BPO) as
an initiator by microwave irradiation has been investigated. The influence of reaction
conditions such as initiator content, monomer content and irradiation time have been
examined. IR spectra of PE and PE-g-MAH show that MAH is really grafted on the PE
in a xylene solution by means of microwave. Moreover, the melting temperature of PE-
g-MAH is lower than that of PE, but the melting enthalpy of PE-g-MAH higher than
that of PE. [50]
2.4. Polymer Nanocomposites
The structures and properties of the composite materials are greatly influenced by the
component phase morphologies and interfacial properties. Nanocomposites are based
on the same principle and are formed when phase mixing occurs at a nanometer
dimensional scale. As a result, nanocomposites show superior properties over their
micro counterparts or conventionally filled polymers.
24
2.4.1. Polymer Nanocomposite Synthesis Methods
Not all physical mixtures of polymer and silicate will form a nanocomposite. The
compatibility between the two phases is important. Nanocomposites are synthesized
from various polymers; nylon 6, polyimide, epoxy resin, polystyrene, polycaprolactone
and acrylic. The exfoliated and homogeneous dispersion of the silicate layers, however,
could be achieved only in few cases, such as polymers containing polar functional
groups such as amides and imides. This is due to the fact that silicate layers of clay have
polar hydroxy groups and are compatible with polymers containing polar functional
groups.[48] Silicate clay layers are bound together by a layer of Na+ or K+ ions and are
naturally hydrophilic.
Ion exchange reactions with cationic surfactants including primary, tertiary and
quaternary ammonium ions render the normally hydrophilic silicate surface
organophilic, which makes intercalation of many engineering polymers possible. The
role of the alkyl ammonium cations in the organosilicates is to lower the surface energy
of the inorganic host and improve the wetting characteristics and, therefore, miscibility
with the polymer.[52]
Nanocomposites can be formed in one of three ways:
• Melt blending synthesis.
• Solvent based synthesis.
• In-situ polymerisation.
2.4.1.1. Melt Blending Synthesis
The melt blending process involves mixing the layered silicate under shear, with the
polymer while heating the mixture above the softening point of the polymer. During
this process, the polymer chains diffuse from the bulk polymer melt into the galleries
between the silicate layers.
In some cases the polymer–silicate mixture can be extruded by using (a) static melt
intercalation: by mixing and grinding dried powders of polymer and organic silicate in a
pestle and mortar and then heating the mixture in vacuum, and (b) extrusion melt
25
intercalation: by extruding the mixture with twin screw extruder to produce a polymer
nanocomposite from the polymer and modified clay.[54,71, 72]
2.4.1.2 Solvent Based Synthesis
The solvent based synthesis involves mixing a preformed polymer solution with clay. A
polystyrene–clay hybrid can be prepared by mixing a polystyrene-toluene solution and
silicate to yield a suspension and then evaporating the solvent. Polyimide–clay hybrids
can be prepared by dissolving clay in dimethylacetamide (DMAC) and mixing with
precursor solution of polyimide and then removing the solvent.[73]
2.4.1.3. In-situ Polymerisation
The clay/organoclay is dispersed in the monomer and the polymerisation reaction is
carried out (Figure 2.7). Polystyrene clay nanocomposites can be prepared by the
polymerisation of styrene in the presence of clay; chemical grafting of polystyrene onto
montmorillonite interlayers have achieved by addition polymerisation reactions.
Thermoset PNCs are prepared by using this method.[78]
Most thermoplastic polymer nanocomposites are produced by either of the first two
methods.[74]
Figure 2.7: Method for creating intercalated polymer-clay architectures via direct polymer contact and via insitu polymerization of pre intercalated polymers.
26
2.4.2. The structure of nanocomposites
Often, there are occasions where retention of the layered nature of a polymer–clay
nanocomposite is the desired outcome. Such regular nanoassemblies have the following
unique characteristics and applications:
1. There are a wide variety of both host materials (clay and nonclay) and polymers.
2. Anisotropic arrangements of polymers in two-dimensional microenvironments occur.
3. The variable gallery spacing is adaptable to polymer size.
4. Microenvironments can induce spatial chemistry and host surface chemistry effects.
5. Rigid host layers provide enhancements to structural, chemical, and thermal
stabilities to more fragile guest polymers.
Two primary methods are utilized to prepare intercalated polymer–clay materials. The
former route is limited because the types of polymers that can be intercalated directly
are limited. The latter route, while more universal, results in a loss of control over the
molecular weight of the final polymer.
Some of the PCN systems are created in a unique way where in the clay layers are
crystallized from a silicate sol-gel in direct contact with a polymer solution. In the
majority of intercalated PCN cases, the linear macromolecules are in nearly fully
extended conformation. Another way to intercalate polymers directly is through a melt
method, where the polymers are heated with a preexfoliated (in most cases) clay. In this
way, a conventional polymer extrusion process can often be utilized. The formation of
PCNs via melt intercalation depends on the thermodynamic interaction between
polymer chains and host layers, and also on the diffusion of polymer chains from bulk
to interlayers. For more hydrophobic polymers, however, the clays must be rendered
more organophilic to enhance their compatibility.
Probably the most successful route to creating PCNs in general has been the in situ
process, wherein monomers are polymerized in the presence of clay mineral layers. In
terms of well-ordered polymer–clay intercalates, using in situ polymerization have
included polyacrylamide, nylon, polyaniline, polycaprolactone, polyimide, PMMA,
27
polystyrene, polyurethane, polyethynylpyridine, and epoxy resins. If conditions are
varied, many of these polymers can also be induced to form exfoliated PCN
architectures.
The dispersion of mineral reinforcing components to a polymeric matrix has been
utilized for many decades. Inactive fillers or extenders act to simply reduce costs, and
their chemistry is less important than factors such as particle size, shape, morphology,
distribution, and, of course, cost. Active fillers are reinforcing materials and require at
least some compatibility between polymer and inorganic, and they must often undergo a
surface modification process to insure this. In contrast to conventionally scaled
composites on the micrometer level, nanocomposites exhibit changes in composition
and structure over the nanometer length scale. Individual clay layers fall into this realm
because they have a thickness on the order of 1 nm. Clays such as kaolinite, mica, and
talc have been important plate-shaped conventional fillers in the past. However,
preparation of a true nanocomposit requires complete dispersion, or exfoliation, of the
elementary clay layers within the polymer matrix, without any aggregation into larger
units such as tactoids or intercalation products. This is a serious challenge that has been
addressed well since the first pioneering research was published in 1987 from Toyota
workers. There are very few successful reports of making fully exfoliated PCNs from
dissolved polymer solutions. This is because even when dispersions of fully exfoliated
clays are exposed to macromolecular solutions, the strong interactions between
macromolecules and silicate layers often just reaggregate the layers. There is a report
that polysulfone exfoliates organoclays via a “solution dispersion” technique. More
success for making the better PCNs has occurred using the melt mixing method
concerning superior composite properties, including more exfoliation. In a study of
PCN synthesis, the PNC structure can also be investigated in the differences in melt
rheology and in the crystalline morphology. As in the case for intercalated materials,
the clays need to be premodified by reaction with alkylammonium ions in order to make
them more compatible with the hydrophobic polymers. The most successful process for
making exfoliated PCNs has been through the polymerization of monomers that are in
the presence of clay minerals. Conditions must be optimized to promote a
28
polymerization that causes the uniform dispersion of silicate layers within the polymer
matrix. The heat of reaction evolved (enthalpy) during polymerization provides an
essential component to the exfoliation. Therefore, exfoliation is enhanced with
increasing amounts of intercalated monomers and with decreasing layer charge on the
clay surface. in situ polymerizations (emulsion, thermal, photo, free radical, etc.) that
employ organoclays and lead to truly exfoliated PCNs.
The main reason for these improved properties in nanocomposites is the interfacial
interaction between the matrix and layered silicate, as opposed to conventional
composites [1]. Layered silicates have layer thickness onthe order of 1 nm, and very
high aspect ratios (e.g. 10∼1,000). A few weight percent of layered silicate particles that
are properly dispersed throughout the matrix can thus create a much larger surface area
for polymer filler interactions than do conventional composites.
Figure 2.8: Shematic representation of the various PNC architectures [10]
On the basis of the strength of the polymer/layered silicate interfacial interaction, three
structurally different types of composites are achievable (Figure 2.8): (1) phase-
29
separated composite, when polymer matrix has no interaction with layered silicate, (2)
intercalated nanocoposites, where insertion of polymer chains into the silicate structure
occurs in a crystallographically regular fashion, regardless of the polymer-to-layered
silicateratio, and a repeat distance of few nanometers, and (3) exfoliated
nanocomposites, in which the individual silicate layers are separated in the polymer
matrix by average distances that totally depend on the layered silicate loading.
2.4.3. Structural Characterization of PNCs
The most commonly used techniques for structural characterisation of nanocomposites
are X-ray diffraction (XRD), SAXS, SEM, transmission electron microscopy (TEM)
and WAXD analysis.
X-ray diffraction allows the determination of the spaces between structural layers of
silicate utilising Bragg’s law: sinθ = nλ /2d. Intercalation and delamination change the
dimensions of the gaps between the silicate layers, so an increase in layer distance
indicates that a nanocomposite has formed. A reduction in the diffraction angle
corresponds to an increase in the silicate layer distance. Generally, diffraction peaks
observed in the low angle region (2θ = 3–9°) indicate the d-spacing (basal spacing, d001)
of ordered intercalated and ordered-delaminated structures. If the nanocomposites are
disordered, no peaks are observed in the XRD due to loss of structure of the layers, the
large d-spacings (>10nm), or both. In general, the following relationship between the
composite and the X-ray diffraction pattern holds [52,71].
Because of its easiness and availability WAXD is used to characterize the
nanocomposite structure and sometimes to study the kinetics of the polymer melt
intercalation. Monitoring the position, shape, and intensity of the basal reflections from
the distributed silicate layers, the nanocomposite structure (intercalated or exfoliated)
can be identified. In an exfoliated nanocomposite, the extensive layer separation
callobrated with the delamination of the original silicate layers in the polymer matrix
results in the final disappearance of any coherent X-ray diffraction from the distributed
silicate layers.
30
Figure 2.9: Wide-angle and small-angle X-ray diffraction of polymer samples.
On the other hand, for intercalated nanocomposites, the finite layer expansion
associated with the polymer intercalation results in the appearance of a new basal
reflection corresponding to the larger gallery height. Although WAXD offers a useful
method to determine the interlayer spacing of the silicate layers in the original layered
silicates and in the intercalated nanocomposites (within 1–4 nm), little can be said about
the spatial distribution of the silicate layers or any structural nonhomogeneities in
nanocomposites.
Additionally, some layered silicates initially do not exhibit well-defined basal
reflections. Thus, peak broadening and intensity decreases are very difficult to study
systematically. Therefore, conclusions concerning the mechanism of nanocomposites
formation and their structure based on WAXD patterns are only temporary. On the
other hand, TEM allows a qualitative understanding of the internal structure, spatial
distribution of the various phases, and views of the defect structure through direct
visualization. However, special care must be exercised to guarantee a representative
cross-section of the sample.[75]
Information about the macrostructure of a polymer such as the dimensions and packing
of crystallites, spherulites, lamellae, separated phases, and voids; particle size and shape
in solution or colloids; and information on branched polymers and the deformation and
31
annealing of polymers can be obtained from small-angle Xray scattering (SAXS). The
reflections that lie very close to the beam stop are necessary for this information. To
obtain sufficient clarity synchrotron radiation is often used. If the sample is reactive
under high intensity X-radiation, this method is unsuitable.
The morphological properties of PNC samples were investigated by the scanning
electron microscope (SEM) which is a type of electron microscope that images the
sample surface by scanning it with a high-energy beam of electrons in a raster scan
pattern. The electrons interact with the atoms that make up the sample producing
signals that contain information about the sample's surface topography, composition
and other properties such as electrical conductivity.
The types of signals made by an SEM can include secondary electrons, back scattered
electrons, characteristic x-rays and light (cathodoluminescence). These signals come
from the beam of electrons striking the surface of the specimen and interacting with the
sample at or near its surface. In its primary detection mode, secondary electron imaging,
the SEM can produce very high-resolution images of a sample surface, revealing details
about 1 to 5 nm in size. Due to the way these images are created, SEM micrographs
have a very large depth of focus yielding a characteristic three-dimensional appearance
useful for understanding the surface structure of a sample. This great depth of field and
the wide range of magnifications (commonly from about 25 times to 250,000 times) are
available in the most common imaging mode for specimens in the SEM, secondary
electron imaging, such as the micrograph taken of pollen shown to the right.
Characteristic x-rays are the second most common imaging mode for an SEM. X-rays
are emitted when the electron beam removes an inner shell electron from the sample,
causing a higher energy electron to fill the shell and give off energy. These
characteristic x-rays are used to identify the elemental composition of the sample.
Back-scattered electrons (BSE) that come from the sample may also be used to form an
image. BSE images are often used in analytical SEM along with the spectra made from
the characteristic x-rays as clues to the elemental composition of the sample.
32
2.4.4. Works on PNC including MAH/EVA Grafting Polyolefins in Recent Years
Polymer-layered silicates are the commonest group of nanocomposites. Although first
reported by Blumstein in 1961, the real exploitation of this technology started in the
1990s.[51] Because of their nanometer size dispersions, nanocomposites exhibit
superior properties in comparison with pure polymer constituents or conventionally
filled polymers. The main advantages are light weight, high modulus and strength,
decreased gas permeability, increased solvent resistance and increased thermal stability.
Their mechanical properties are superior to unidirectional fibre-reinforced polymers
because reinforcement from the inorganic layers will occur in two rather than in one
dimension.[52] Because of the length scale involved that minimises scattering,
nanocomposites are usually transparent.[53] They also exhibit significant increases in
thermal stability as well as a selfextinguishing character. In polymer-layered silicates,
composite properties are achieved at a much lower volume fraction of reinforcement in
comparison with conventional fibre or mineral-reinforced polymers. They can be
processed by such techniques as extrusion and casting common to polymers which are
superior to the costly and cumbersome techniques used for conventional fibre and
mineral-reinforced composites and furthermore are adaptable to films, fibres and
monoliths. Most of the work in this area is at present at the experimental stage, although
some commercial explonation has been reported. For example, the Toyota Motor
Company is using an automotive timing-belt cover made from a nylon-layered silicate
nanocomposite. Potential applications are barrier films for food packaging, aeroplane
interiors, fuel tanks and components in electrical or electronic parts, brakes and
tyres.[54]
Wang and his co-workers prepared maleated polyethylene/silicate nanocomposites with
a different aspect ratio of silicate and maleated polyethylene/SiO2 composite by melt
intercalation. The nanocomposites with a high aspect ratio silicate (montmorillonite)
showed a faster decrease in the terminal slope of the storage modulus and a steeper
increase in complex viscosity than those with a low aspect ratio silicate (laponite) and
SiO2. The addition of montmorillonite increases the crystallization and the melting
temperature of maleated polyethylene but decreases above 3 vol % of the silicate
33
content because of the increased viscosity. The nanocomposite with montmorillonite
showed the highest yield strength and secant modulus among the composites because of
the highest aspect ratio of the filler. It also revealed strong interfacial adhesion with the
matrix and orientation during tensile deformation.[55]
In one study Gopakumar and his co-workers used to the melt compounding to prepare
conventional composites of montmorillonite clay and polyethylene (PE) as well as
nanocomposites of exfoliated montmorillonite platelets dispersed in a maleated
polyethylene matrix. PE/clay composites behaved in a similar manner as conventional
macrocomposites, exhibiting modest increases in their rheological properties and
Young's modulus. Conversely, the nanoscale dimensions of the dispersed clay platelets
in the nanocomposites led to significantly increased viscous and elastic properties and
improved stiffness. This was attributed to the high surface area between the polymer
matrix and the exfoliated clay, which resulted in enhanced phase adhesion.[56]
In study of Mishra and his co-workers, a thermoplastic polyolefin (TPO)/organoclay
nanocomposite was prepared by using maleic anhydride modified polypropylene as a
compatibilizer in melted state. It was shown that the nanocomposite exhibited
remarkable improvement of tensile and storage modulus over its pristine
counterpart.[57]
In a study on PNC, three cationic surfactants (hexadecyltrimethylammonium chloride,
hexadecyldimethylbenzylammonium chloride, and octadecyltrimethylammonium
chloride) were used to modify montmorillonite and polyethylene (PE)/maleic anhydride
grafted polyethylene (PE-g-MAH)/organic-montmorillonite (Org-MMT)
nanocomposites, prepared by two blending processes (direct melt blending and solution
blending). It was found that the intercalation effect of PE/PE-g-MAH/Org-MMT could
be enhanced by increasing the content of PE-g-MMT, using the silicate modified by a
cationic surfactant with a benzyl group or long alkyl chain, adopting the
solutionblending method or using high-density polyethylene as matrix. Org-MMT and
PE-g-MAH had a heterogeneous nucleation effect on crystallization of PE from the
melt, resulting in a decrease of crystalline thickness, and the heterogeneous nucleation
effect was more evident in the nanocomposite made by the solution-blending method
34
than in that made by the direct-melt intercalation process. The tensile strength initially
increased and then decreased with increasing contents of PE-g-MAH. [58]
Zanetti and Costa worked on the polymer composites based on organically modified
clay (organoclay) and prepared polyethylene (PE) by melt processing to study their
combustion behaviour. Formation of intercalated nanocomposites was observed only in
presence of poly(ethylene-co-vinylacetate), added as a compatibilizer. In reason of the
low polarity of PE, the compounding of the molten polymer with a clay modified with
octadecylammonium does not lead to the formation of a nanocomposite. Adding 1 wt%
of EVA containing 19 wt% of vinylacetate is enough to promote intercalation whereas
increasing the amount of EVA to 5 wt% the interaction between the polymer matrix and
the organoclay increases. The nanocomposite showed a reduced rate of combustion due
to the accumulation of the silicate on the surface of the burning specimen which create
a protective barrier to heat and mass transfer. [59]
In another study Zanetti and co-workers prepared Polymer nanocomposites based on
organically modified clay (organoclay) and polyethylene (PE) by melt processing using
poly(ethylene-co-vinyl acetate) (EVA) as compatibilizer. During the thermal
degradation of the nanocomposite in oxidant atmosphere the formation of a protective
layer on the polymer surface was observed caused by a charring process of PE, which is
normally a non-char-forming polymer. The protective effect of the char/clay layer
against thermal oxidation was also observed by monitoring the retention of the long
chain structure of PE.[60]
Zhai and his co-workers chemically modified the polyethylene (PE) with grafting
maleic anhydride (MAH) monomer on its backbone at first. Then the melt-direct
intercalation method was employed to prepare two kinds of nanocomposites,
polyethylene (PE)/organic montmorillonite (Org-MMT) and maleic anhydride grafted
polyethylene (PE-g-MAH)/Org-MMT nanocomposites. The results show that an
intercalated structure would be acquired on mixing the PE and Org-MMT; and an
almost exfoliated system would be obtained by mixing the PE-g-MAH and Org-MMT.
Moreover, further measurements via thermogravimetric (TGA) and differential
scanning calorimetry (DSC) showed that both of the nanocomposites had a higher
35
thermal decomposition temperature and a higher crystallization temperature when
compared to the original matrix. [61]
In the study of Morawiec nanocomposites based on low density polyethylene,
containing of 3 or 6 wt.% of organo-modified montmorillonite nanoclay (MMT-ODA)
and maleic anhydride grafted low density polyethylene as a compatibilizer were
prepared by melt mixing. The compatibilized nanocomposites exhibit improved thermal
stability in air as compared to neat polyethylene and nonexfoliated MMT-ODA
composite. Scanning electron microscopy and density measurements of drawn samples
indicated the existence of pores in noncompatibilized composite while no pores and
good adhesion to MMT-ODA are found in compatibilized nanocomposites.[62]
In a study of Kim, effect of maleated polyethylene on the rheological properties of
LLDPE/clay nanocomposites has been investigated. It was shown that the
nanocomposites of adding a MA-g -PE showed unusual rheological properties such as
high shear thinning tendency and elastic property.[63]
Ratnayake and Haworth worked on the influence of low molecular weight additives
containing polar groups and modified polyolefin-based compatibilizers on
polypropylene (PP)-clay nanocomposites (PPCN), in terms of intercalation and degree
of exfoliation achievable by melt-state mixing processes. PPCN were prepared by melt
mixing two PP homopolymers with organically-modified montmorillonite type clay, in
the presence of maleic anhydride-grafted polypropylene (PP-MA) compatibilizer. XRD
analysis shows that interlayer spacing of clay has been increased dramatically, while
TEM results show a significant improvement of clay dispersion in the PP matrix, when
nanocomposites are prepared with commercial PP containing short-chain organic
additives with polar end groups. The interaction between polar group (NH2) of this
additive and the polar sites on the filler surface appears to be the driving force for the
intercalation.[64]
The effects of ethylene vinyl acetate copolymer ( EVA) as a compatibilizer on the
dispersion of organically modified montmorillonite( org-MMT) into low-density
polyethylene ( LDPE ) during melt extrusion compounding were studied. Exfoliated
LDPWorg-MMT nanocomposites in the presence of an EVA compatibilizer could be
36
prepared by using a two-step melt compounding technique with a twin-screw
extruder.[65]
In one of the studies, the use of low molecular weight oxidized polyethylenes (OxPE)
with different molecular weight and acid number as a new type of compatibilizer in low
density polyethylene (LLDPE)/org-clay nanocomposite preparation was examined.
Nanocomposites having 5 phr (part per hundred) org-clay were prepared by melt
processing. The effect of compatibilizer polarity and clay dispersion on the thermal,
mechanical and barrier properties of the nanocomposites was investigated. It was
observed that oxidized polyethylenes created a strong interfacial interaction between the
clay layers and polymer phase based on the analysis of the linear viscoelastic behavior
of the samples by small amplitude oscillatory rheometry. We showed that physical
performance of the nanocomposites is not only affected by clay dispersion but also both
melt viscosity and polarity of the oxidized polyethylene compatibilizers. It was found
that oxygen permeability values of the nanocomposite samples prepared with the
oxidized polyethylenes were lower than that of a sample prepared with conventional
compatibilizer, maleic anhydride grafted polyethylene (PE-g-MA).[66]
Saminatan prepared polypropylene (PP)/Montmorillonite (MMT) nanoclay based
composite by melt compounding with maleic anhydride grafted polypropylene (MA-g-
PP) as a compatibilizer in a twin-screw extruder, and the test specimens were injection
molded. PP/clay nanocomposite shows 25% improvement in specific EWF compared to
pure PP. The variation of EWF parameters with loading rate is discussed, whilst the
mechanisms of fracture are considered in a subsequent paper.[67]
In one study Golebiewski and his co-workers prepared Low density polyethylene
nanocomposites using differently modified montmorillonite (MMT) and different
compatibilizers. The best results were obtained for MMT with largest gallery distance.
It indicated that the compatibilizer was preferentially located around clay platelets and
did not enter the amorphous layers of polyethylene. Also the orientation of clay
platelets was determined by FTIR using 1080 cm_1 band characteristic for Si–O bonds.
A clear correlation of oxygen permeativity of blown films with clay platelets orientation
and degree of exfoliation was evidenced.[68]
37
3. EXPERIMENTAL PART
3.1. Chemicals Used
3.1.1. Low Density Polyethylene (LDPE)
Low density polyethylene was obtained from PETKIM Petrochemical Holding
(G03-5). Its number averaged and weight averaged molecular weights were 20 300
g/mol and 213 600 g/mol, respectively.
3.1.2. Linear Low Density Polyethylene (LLDPE)
Linear low density polyethylene was obtained from Exxon Corp. Its density was
0.91-0.925 g/ cm3.
3.1.3. Itaconic Acid (IA)
CH2 ║ HOOC – CH2 – C – COOH
Systematic name, 2-methylene succinic acid, was the product of Fluka A. G. With a
99% purification, was used without any purification procedure. (m.p. = 165- 167 0C)
3.1.4. Itaconic Monoesters
Monomethyl itaconate (MMI), monobutyl itaconate (MBI), and monooctyl itaconate
(MOI) was used as monoesters which has been prepared before by the procedure
which is described in the literature. [8]
3.1.5. Sodium Montmorillonite
The nanofiller (Nanofil 757), sodium-montmorillonite (Na-MMT), used in the
preparation of organoclay was received from Süd-Chemi Inc. It is a highly purified
natural Na-MMT with cation-exchange capacity (CEC) of 0.080 meq/g, average
particle size< 10 meq, and bulk density of approximately 2.6 g/mL.
38
3.1.6. Dodecyl amine (DDA)
With the formula C12H27N dodecyl amine is an alifatic amine and its molecular
weigth is 185.36 g/mol . It was recived from ”Merck” and was used without any
purification (MP = 25-28 0C).
3.1.7. Hexadecyl amine (HDA)
With the formula C16H35N hexadecyle amine is an alifatic amine and its molecular
weight is 241.46 g/mol. It was received from ”Merck” and was used without any
purification (MP = 43-46 0C).
3.1.8. Octadecyl amine (ODA)
With the formula C18H39N octadecyl amine is an alifatic amine and its molecular
weigth is 269.52 g/mol . It was recived from ”Merck” and was used without any
purification (MP = 52-56 0C).
3.1.9. Dibenzoyl Peroxide (DBPO)
It was used as the initiator, which is a product of Peroxide Chemie GmbH
(München, Germany).
3.1.10 Xylene
It was used as the solvent, which is a product of Merck A.G.,
3.1.11. Isopropyl Alcohol
It was used for analytical measurements as the solvent, which is a product of Merck
A.G.
3.1.12. Methyl Alcohol
It was used for precipitation of reacted samples, obtained from Merck A.G.
3.1.13. Ethyl Alcohol
It was used for analytical measurements as the solvent, which is a product of Merck
A.G.
39
3.1.14. Potasiumhydroxide (KOH)
It was used for analytical measurements purchased from Merck A.G.
3.1.15 Hydrochloric Acid (HCl)
% 37 HCl solution, which is a product of Merck A.G., was used for analytical
measurements.
3.1.16. Sodiumcarbonate (Na2CO3. H2O )
It was used for analytical measurements purchased from Merck A.G.
3.1.17. Bromothymol Blue
It was used as the indicator for back titration of product samples.
3.1.18. Methylene Red
It was used as the indicator for standardizing titration solutions.
3.2. Equipment Used
3.2.1. Magnetic Stirrer with Heater
It was used for heating and mixing of product sample in xylene solvent for
analytical measurement work. This instrument has a maximum mixing rate of 1250
rpm and it can be heated to a maximum temperature of 300°C.
3.2.2. Vacuum Oven
WTC Binder model oven used at the 600C to remove the residual methanol and
xylene on grafted polymer samples.
3.2.3. Microwave Oven
Vestel MD 930 model MW applicator has the sizes as 335x339x245 mm (WxHxD),
energy outgoing power as 1000 W and MW frequency as 2.45 GHz. This oven has
ten MW levels at the range of 10-100. All experiments were run at first level, which
is equal to 100 W power, fixing the temperature to 1400C.
40
3.2.4. Extruder
We used MiniLab extruder to prepare the polymer nanocomposites by melt mixing
method. This MiniLab extruder is HAAKE MiniLab Micro Compounder which is
ensured from Thermo Electron Company. Corotating twin screw extruders motor
power of is 400W, screw speed range is 1-360 rpm, and maximum torque is
5 Nm/screw. Maximum internal temperature of extruder is 350 0C. Barrel internal
value is 3.5 cm3 and total volume of cycle capacity is 5.5 cm3.
Figure 3.1: HAAKE MiniLab Micro Compounder
Figure 3.2: Control panel of the MiniLab extruder.
41
3.2.5. XRD Analysis
X-ray diffraction analysis (XRD) is a nondestructive method for the structure
analysis of crystals. The sample is irradiated with monochromatic X-ray light and
the stray radiation recorded. An important field of application is the identification of
crystalline fractions in samples. Measurement were made by using Shimadzu XRD
6000 Model diffractometers CuKα radiation and the used wave length is
λ=1.5405 Å.
3.2.6. Mechanical Test Device
To obtain mechanical properties of polymer nanocomposites, mechanical tests were
made by using Alfred J. Amster Company’s elongation test device (ADKT 10M–
V190). Maximum weight capacity of the elongation device is 200 kg and maximum
speed of the device is 50 min.cm-1. (It could work in 5-18-30 and 50 min.cm-1 )
3.2.7. Shore-D Hardness Test Device
Shore-D hardness of samples was measured with Zwick Shore-D durometer by
using ASTM D 2240. Easy readable scale of the device is between 0-100 digit. This
portable device gives us highly sensitive shore-D hardness values.
Figure 3.3: Shore-D hardness measure device.
3.2.8. Melt Flow Index Device
Melt flow index (MFI) is a value which consists of melt flow rate (MFR) and melt
flow rate (MVR) values. MFR is the weight of flowed sample in a certain time (g/10
min.) MVR is the volume of flowed sample in a certain time (cm3/10 min.) under
2.16 kg load. HAAKE Melt Flow MT is used to measure MFR and MVR values of
sample. (Figure B3)
42
Table 3.1: Test conditions and standarts according sample type.
Plastic
material
DIN
53735
DIN ISO
1133
ASTM
1238
Temperature
( ºC)
Weigth (kg)
PE
D
G
T
4
7
15
E
G
P
190 2.16
2.16
5.00
Figure 3.4: “Melt Flow Index” MFI device.
Table 3.2: Average MFI values with used weight usen in cylinder and measure
time.
MFI-values Weight used in cylinder Measure time
0.1 - 0.5 3 - 5 g 240 sec >0.5 - 1 4 - 5 g 120 sec
>0.5 - 1 4 - 5 g 60 sec
>0.5 - 1 6 - 8 g 50 sec
>0.5 - 1 6 - 8 g 5 - 15 sec
MFR device
MT unit
Measuring piston and standart weight
43
Figure 3.5: Schematic representation of MFI device
3.3. Experimental Procedure
3.3.1. Preparation and Purification of Grafted Polyolefins
All grafting reactions were carried out at 140 0C with 100 W microwave input
power. Polyolefin was dissolved in xylene then was mixed together with DBPO and
monomer in a certain proportion. In all experiments, the weight ratio of xylene to
polyolefins is always 10/1.
A little amount of ethanol was added to mixture in order to dissolve monomers
better in the reaction solution. The mixtures are put into the microwave applicator,
irradiated for the expected time, and then removed. The samples were purified by
dissolving in xylene and precipitating in methyl alcohol two times to be sure of the
removal of unreacted monomers, and then dried in vacuum at 600C. The products
were used to determine the grafting ratio (GR).
Graft copolymers which were used as compatibilizers were obtained by grafting
LDPE and LLDPE polyolefins with IA, MMI, and MBI in 100 W microwave at
1400C.
44
3.3.2. Preparation of Organoclays
DDA, HDA, and ODA modified clays were prepared the procedure given in the
literature.[76]
3.3.3. Preparation of Polymer Nanocomposites (PNC)
Single step melt mixing method was used to prepare PNCs for all samples. For this
purpose, optimization conditions were determined at different temperatures, cycling
time and rotational speed for single step melt mixing in MiniLab twin screw
extruder. During the optimization, the important criteria were to prevent the
degradation and shark skin effect, and to provide the homogeneity of polymer
nanocomposites.
Several extruder temperatures were tried between 165-190°C to determine an
optimum temperature, which will allow easy processing and prevent degradation of
polymer nanocomposites for 85 rpm and 3 min. cycling time. It was shown that at
high set temperatures, polymer nanocomposites underwent to degradation, while at
low temperatures homogeneous polymer nanocomposites could not be achieved and
moreover shark skin effect occurred.
For determining the rotational screw speed, the experiments were done within the
range of 60-110 rpm screw speeds for 177 °C and 3 min. cycling time. The suitable
screw speed for the processing of PNC was determined as 87 rpm, because in the
speeds of lower than this value “shark skin effect”, in the speeds of higher than this
value degradation occurred.
A cycling time was optimized for the process to provide a homogeneous dispersion
of organoclay in matrix and prevent degradation of PNC. In addition, it was
important to choose a short cycling time to increase out-put of the process. In the
pre-works, to determine the influence of the cycling time on homogeneity, surface
appearance and out-put, the experiments were done within the range of 2-7 min.
Consequently, optimization conditions were determined as 177 °C set temperature,
87 rpm screw speed with 2 min. cycling time.
45
3.4. Tests and Analyses
3.4.1. Measurement of Grafting Ratio by Analytical Method
A small amount (0.2-0.4g) of grafted polyolefin was dissolved and heated to 110 °C
with reflux in 100 mL xylene for 30 min, followed by cooling to 60 °C. 30
milliliters 0.005 N potassium hydroxide (KOH)/ethanol solution was added, and the
mixture was heated under reflux for 15 min. The alkali concentration was
determined by acid titration using 0.005 N hydro-chloride (HCl)/ isopropanol
solution. The indicator was 0.1% bromothymol blue/ethanol solution. A blank was
carried out by the same method.
Grafting degree is expressed by the following equation:
GR = N(V0 –V) x MW x 100 % (3.1)
n x W x1000 where N is the concentration of HCl/ isopropanol(mol/L), W is quantity of sample
(g), V is the volume of HCl/ isopropanol used by titration, V0 is the volume of HCl/
isopropanol used in a blank assay, MW is the molecular weight of monomer and n
is the number of carboxyl group on the monomer.
3.4.2. XRD Analysis
X_Ray diffraction (XRD) patterns of the samples were recorded by monitoring the
diffraction angles (2θ) from 10 to 150 on the apparatus by using CuKα radiation .
Bragg equation (λ n = 2 d sin θ ; n=0,1,2,...) is the well-known fundamental law of x-
ray crystallography. Interplanar spacing is d, the angle between the planes and the
direction of the beam is θ, λ is wavelength used light, and n is integer. The angle
between reflected wave and solid surface is θ. λ=1.5405 Å. a parameter for the used
apparatus. The data obtained from instrument were 2θ vs intensity and the first
interlayer spacing, d0, values were calculated from the plot given by using Bragg
equation with given constants and taken the integer n=1.
3.4.3. Mechanical Test
From the measured stress and strain values, elongation at break, stress at break, 1%
secant modulus, which is the slope of a line drawn from the origin to 1 % strain on
46
the stress-strain curve, and toughness values were calculated from the average of at
least 4 specimens tested. For the comparing of the mechanical improvements on the
PNCs, mechanical properties of original LDPE and LLDPE were measured and
calculated. 18 min./cm constant elongation speed and 20 kg maximum weight was
used for the measurements.
3.4.4. Shore-D Hardness Test
The samples that were prepared in extruder were used for hardness test. According
to standard measurement (ASTM D 2240); the beginning measured value and after
the 20 seconds value were recorded. For every sample, 5 parallel values measured
and the averages of the values were calculated and recorded.
3.4.5. Melt Flow Index Test
Determination of the melt flow rate, MFR, measurements followed DIN 1133. The
effects of compatibilizer on the melt flow properties of the PNCs were determined
by calculating the normalized values of MFR (n-MFR) and MVR (n-MVR). [65]
For this purpose, MFR and MVR measurements were also applied to control units.
The corresponding control units contained matrix polyolefin and the different
percentages of compatibilizers. The normalized MFR and MVR values calculated
by equation given as follows:
unitcontrolingcorrespondofrateflowMelt
itenanocomposofrateflowMeltrateflowmeltNormalized = (3.2)
47
4. RESULTS AND DISCUSSION
In this work, polymer nanocomposites (PNC) which contain compatibilizer and
organoclay in polyolefin (PO) matrix were synthesized. For preparing PNCs,
organically modified Na-MMT were mixed with PO and compatibilizer in counter
rotating twin screw extruder by a single step method. Pre-works were done in order
to determine the optimum extrusion conditions in minilab extruder of samples.
4.1. The Optimization of Compounding Conditions
Optimization experiments for PNC compounding were done at different
temperatures, cycling times and rotational speeds to determine optimum conditions
for single step melt-mixing method in MiniLab extruder. The important criteria
chosen for determining of the optimization conditions were to investigate the
degradation and shark skin effect. High temperatures and long cycling times cause
to degradation while high rotational speeds cause to shark skin appearance. Several
extruder temperatures were tried between 165-190°C to determine an optimum
temperature to provide the homogeneity of PNCs. It was shown that at high set
temperatures, polymer nanocomposites underwent to degradation, while at low
temperatures homogeneous polymer nanocomposites could not be achieved. For
determining the rotational screw speed, the experiments were done within the range
of 60-110 rpm screw speeds. The suitable screw speed for the processing of PNC
was determined as 87 rpm, because this was the limit speeds of for shark skin effect.
A cycling time was optimized for the process to provide a homogeneous dispersion
of organoclay in PO matrix and prevent the degradation of PNC. For higher values
than this value, the degradation occurred. In addition, it was important to choose a
short cycling time to increase out-put of the process. In the pre-works, to determine
the influence of the cycling time on homogeneity, surface appearance and out-put,
the experiments were done within the range of 2-15 min. cycling time.
Consequently, optimization conditions were determined as 177°C mixing
temperature, 87 rpm screw speed with 2 min. cycling time.
48
4.2. Synthesis Conditions for Characterization of Samples
The 54 samples were prepared by using 2 different types of POs (LDPE and
LLDPE), 3 different types of organoclays, and 3 different types of compatibilizers.
The experimental techniques for the preparation of compatibilizers were explained
in Section 3.3.1. The grafting degrees of the IA and its monoesters were given in
Table 6.1 and Table 6.2. The methods used for the preparation of organoclays and
PNCs were given in Section 3.3.2 and 3.3.3, respectively. The PNCs contained 5-
wt% of each organoclay and 3 concentration levels of each of compatibilizers. Each
sample description refers to a specific composition involving the components used
in the preparation of the samples (Table 6.3 and Table 6.4).
4.3 XRD Analysis Results
The results of the XRD measurements of samples are given in Table 6.5, Table 6.6
and some of the XRD patterns are given in Figures 4.1-4.4.
From the diffraction values, the distance between clay layers (d001) of original clay
Nanofil 757 was calculated from the Bragg equation as 13.6 Å (Figure 6.1 and
Table 6.5). Modification of clay increased the distances between clay layers and
modification with DDA (ODDA), HDA(OHDA) and ODA(OODA) showed d001 values
as 26.4 Å, 29,9 Å and 31,5 Å respectively. These results calculated from the XRD
patterns. An increase in the chain length of the surface-active modifying agent
caused an increase in the interlayer spacing.
The distance between clay layers was increased by adding of the compatibilizer due
to the penetration ability of compatibilizer into the layers. According to data
determined from experiments, given in tables, it can be said that increasing of
compatibilizer content increases the dispersion of the organoclay in matrix. 5 %
compatibilizer addition was not very effective in increasing in the interlayer spacing.
However, addition of w ≥ 10- wt% compatibilizer significantly improved clay
dispersion. So the observed shifts of diffraction peaks increase with increasing value
of percent compatibilizer in the nanocomposites. Prepared PNC samples were
achieved in the forms of intercalated or exfoliated depending on the type and the
content of organoclay and grafted polar groups.
With increasing of the side chain length on ester group, the grafting ability of ester
decreases. The mole percent grafting ratio were taken nearly the same, but two polar
49
group containing IA grafting was more effective than those of monoesters as
expected. The best layer spacing was obtained for the samples of LDPE-IA-OHDA5-
10, LDPE-IA-OHDA5-C15, LDPE-MMI-OHDA5-C15, LLDPE-IA-OODA5-C15, and
LLDPE-MBI-ODDA5-C15. The complete exfoliation was observed for these
nanocomposite.
4.4. Mechanical Characterization Test Results
4.4.1. Tensile Tests Results
Tensile test were applied to polymer nanocomposite samples. Tensile 1% secant
modulus, maximum strength, strength of break, strain of break, and toughness at
break of PNCs were obtained from the 4 samples averaged. The calculated results
were given in Table 6.7 and Table 6.8. According to these values, for the samples
which do not include compatibilizer, addition of 5% organoclay decreases the
elongation at break but increases other mechanical properties. In general, increasing
the compatibilizer content increased all the mechanical properties due to increased
interlayer spacing. Moreover, all the mechanical properties of polymer
nanocomposite samples increase by adding compatibilizer. Because compatibilizer
penetrates in to the clay layers, dispersion of organoclay in nanocomposite
increases. The increase in the mechanical properties also depended on the chain
length of the surface-active modifying agent used for the modification of the clay.
Because of good dispersion of organoclay in polymer matrix, the mechanical
properties increase by increasing percentage of the compatibilizer.
When we look at the elongation at break values, in the LLDPE-IA-ODDA 5-C15 the
elongation %23 higher then LLDPE-ODDA5, in the LLDPE-IA-OHDA 5-C15 the
elongation 33% higher then LLDPE-OHDA 5, and in the LLDPE-IA-OODA 5-C15 the
elongation 44% higher then LLDPE-OODA 5. These values showed us increasing
percentage of compatibilizer increases the elongation at break significantly.
We calculated 1% secant module instead of Young module, therefore the strength-
strain pattern of polyolefins showed curvature starting from the origin, generally.
1% secant modulus is the slope of the line between origin and concurrence of %1
elongation and the stress value at 1% elongation. When we look to these values we
observe that increasing compatibilizer content increases %1 secant modulus. The
highest values were achieved in the samples including 15% compatibilizer. On the
50
other hand, the addition of 5 % compatibilizer was not very effective due to its
ineffectiveness of interlayer spacing. Using compatibilizer content higher than 5 %
can also increase 1 % secant modulus up to 68 %.
Addition of IA containing compatibilizers was more effective than its monoesters.
The increase in the mechanical properties also depended on the chain length of the
surface-active modifying agent used for the modification of the clay. The exfoliated
sample indicated the best mechanical properties.
4.4.2. Hardness Tests Results
Shore-D hardness measurement experiments were carried out with two types
compatibilizer (IA and MMI) and organoclays preapared with HDA containing
polymer nanocomposites. These experiments were performed for both polyolefins in
accordance with the standarts indicated in Section 3.4.4. All the results were given
in Table 6.9
A 10 unit decrease in Shore-D hardness in the second measurements, as is observed
from the table, is a typical thermoplastic behavior. In PNC samples as percent of
compatibilizer increases hardness decreases for both polyolefins. Samples
containing compatibilizers with MMI have greater hardness values then those with
IA. Since LLDPE have lower hardness values then LDPE, if they are compared on
the basis of their compatibilizer and organoclay contents, PNC samples prepared
with LLDPE have lower hardnesses than PNC samples prepared with LDPE.
4.5. Melt Flow Index Test Results
The influences to the processability of different types of compatibilizers with
varying percentages to the polymer nanocomposites were observed by melt indeces
measurements. MFR and MVR values of PNC samples were given in Table 6.10.
MFI is a pressure-imposed, capillary flow experiment and was used to study the
relationship between low strain rate shear flow properties and clay structure in
nanocomposites and the interaction between clay and matrix of PNC samples.
To investigate the effect of compatibilizers and clay structure on PNC, the interaction
between clay and bulk PE, the ‘control’ polymer matrix effect should be excluded.
For his purpose, a normalized MFI (n-MFI) values were calculated and then the results
51
were compared. The corresponding control units contained matrix polyolefin and the
different percentages of compatibilizers. MFI measurements involved MFR and
MVR measurement. MFR and MVR measurements were also applied to the control
units.
Control units were prepared in the extruder, with 5%, 10%, 15% w/w compatibilizer
without containing any organoclay. According to data given in Table 6.10,
increasing the compatibilizer content in the nanocomposite increased n-MFR and n-
MVR values. The normalized values showed an increase with increasing
compatibilizer percent in the nanocomposites.
The results showed that n-MFR and n-MVR values of polymer nanocomposite
samples in the LDPE matrix with IA containing compatibilizer, decrease when the
chain length of the surface active agent of organoclay increases. On the contrary, n-
MFR and n-MVR values of the samples, which contain MMI as a comonomer in
compatibilizer, increase when the chain length of the surface active agent of
organoclay increases.
When we compared the samples with LDPE matrix and LLDPE matrix, the
samples which contain LLDPE showed opposite behavior.
It can be said, the increasing of n-MFR and n-MVR values, the processability of
polymer nanocomposite has been increased.
52
5. CONCLUSION
Intercalated and exfoliated PNC samples containing LDPE and LLDPE polyolefins
were prepared. Polyolefin type, the chain length of surface active agent used for clay
modification, the compatibilizer type and contents affected the PNC samples from
intercalated to exfoliated structure.
The PNC samples were prepared in MiniLab twin screw extruder at 177°C mixing
temperature, 87 rpm screw speed with 2 min. cycling time. The prepared 54 samples
were investigated structural, mechanical and processing points of view. 3 different
types of organoclays were prepared by modifying with 12, 16, 18 carbon chain
length surface active agents. The chain length of surface active agents affected all
the properties of PNCs for both polyolefins. The content of organoclay was kept
constant as 5%.
3 different types of compatibilizers were prepared by grafting of PE matrix with
polar group containing monomers. IA has two polar groups, while MMI and MBI
has one polar group on each monomeric unit. So IA grafted modifiers have two
polar groups and then IA is more effective than those of monoesters. Since IA has
two carbonyl group and monoesters have one, grafting reactions was carried out as
mole comonomer / weight polymer in order to compare the effects of the grafted
samples easily. Therefore, monoesters mole ratios were chosen as twice of mole
ratio of IA. With increasing of the side chain length on ester group, the grafting
ability of ester decreases. The contents of compatibilizers was changed as 5%, 10%,
and 15%. Then, PNC samples contained at least 80% matrix polyolefin.
The mole percent grafting ratio were taken nearly the same, but two polar group
containing IA grafting was more effective than those of monoesters as expected.
The best layer spacing was obtained for the samples of LDPE-IA-OHDA5-10, LDPE-
IA-OHDA5-C15, LDPE-MMI-OHDA5-C15, LLDPE-IA-OODA5-C15, and LLDPE-
MBI-ODDA5-C15. The complete exfoliation was observed for these nanocomposite.
The complete exfoliation can also be obtained depending on the type and the content of
grafted polar groups.
The mechanical properties were measured tensile testing. elongation at break, stress at
break, 1% secant modulus, which is the slope of a line drawn from the origin to 1 %
53
strain on the stress-strain curve, and toughness values were calculated from
measured values. The calculated mechanical properties of PNCs showed an increase
with increasing compatibilizer content, although 5% compatibilizer addition was not
very effective for the systems. Addition of IA containing compatibilizers was more
effective than its monoesters. The increase in the mechanical properties also
depended on the chain length of the surface-active modifying agent used for the
modification of the clay. The exfoliated sample indicated the best mechanical
properties.
The processability of PNC samples were investigated by the normalized values of
MFR (n-MFR) and MVR (n-MVR). Increasing of n-MFR and n-MVR values with
increasing compatibilizer content in the nanocomposites resulted that processability of
nanocomposites was improved by addition of these grafted PE compatibilizers.
54
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58
6. APPENDIX
Table 6.1: Grafting degree of LDPE with IA and monoesters (GD) and grafting percentage (GP). ([DBPO]= 0.75 g /100 g LDPE, T=1400C, MW power = 100 W)
Monomer Monomer Conc. (mol /100 g LDPE)
GD % (mol/100g LDPE)
GD, % (g/100 g LDPE)
GP (g/100 g LDPE)
IA 0.01538 mol (2.0 g) 0.001115 0.145 7.25
MMI 0.01538 mol (2.2 g) 0.002232 0.321 14.52
MBI 0.01538 mol (2.9 g) 0.001997 0.371 12.98
Table 6.2: Grafting degree of LLDPE with IA and monoesters (GD) and grafting percentage(GP). ([DBPO]= 0.75 g /100 g LLDPE, T=1400C, MW power = 100 W)
Monomer Monomer Conc. (mol /100 g LLDPE)
GD% (mol /100 g LLDPE)
GD % (g / 100 g LLDPE)
GP (g/100 g LLDPE)
IA 0.01538 mol (2.0 g) 0.00058 0.0845 4.23
MMI 0.01538 mol (2.2 g) 0.001241 0.1728 7.85
MBI 0.01538 mol (2.9 g) 0.001185 0.2204 7.60
Table 6.3: Sample descriptions and contents of samples which contain LDPE
Sample Description Polyolefine Compatiblizer Organoclay % Compatibilizer %
LDPE-O0-C0 LDPE --- 0 0 LDPE-IA-O0-C5 LDPE LDPE-g-IA 0 5 LDPE-IA-O0-C10 LDPE LDPE-g-IA 0 10 LDPE-IA-O0-C15 LDPE LDPE-g-IA 0 15 LDPE-MMI-O0-C5 LDPE LDPE-g-MMI 0 5 LDPE-MMI-O0-C10 LDPE LDPE-g-MMI 0 10 LDPE-MMI-O0-C15 LDPE LDPE-g-MMI 0 15 LDPE-MBI-O0-C5 LDPE LDPE-g-MBI 0 5 LDPE-MBI-O0-C10 LDPE LDPE-g-MBI 0 10 LDPE-MBI-O0-C15 LDPE LDPE-g-MBI 0 15 LDPE-OHDA 5-C0 LDPE --- 5 0 LDPE-OHDA 10-C0 LDPE --- 10 0 LDPE-OHDA 15-C0 LDPE --- 15 0 LDPE-ODDA 5-C0 LDPE --- 5 0
59
LDPE-ODDA 10-C0 LDPE --- 10 0 LDPE-ODDA 10-C0 LDPE --- 15 0 LDPE-OODA 5-C0 LDPE --- 5 0 LDPE-OODA 10-C0 LDPE --- 10 0 LDPE-OODA 10-C0 LDPE --- 15 0 LDPE-IA-OHDA 5-C5 LDPE LDPE-g-IA 5 5
LDPE-IA-OOHDA 5-C10 LDPE LDPE-g-IA 5 10
LDPE-IA-OHDA 5-C15 LDPE LDPE-g-IA 5 15
LDPE-MMI-OHDA 5-C5 LDPE LDPE-g-MMI 5 5
LDPE-MMI -OHDA 5-C10 LDPE LDPE-g-MMI 5 10
LDPE-MMI -OHDA 5-C15 LDPE LDPE-g-MMI 5 15
LDPE-MBI-OHDA 5-C5 LDPE LDPE-g-MBI 5 5
LDPE-MBI -OHDA 5-C10 LDPE LDPE-g-MBI 5 10
LDPE-MBI -OHDA 5-C15 LDPE LDPE-g-MBI 5 15 LDPE-IA-ODDA 5-C5 LDPE LDPE-g-IA 5 5
LDPE-IA-ODDA 5-C10 LDPE LDPE-g-IA 5 10
LDPE-IA-ODDA 5-C15 LDPE LDPE-g-IA 5 15
LDPE-MMI-ODDA 5-C5 LDPE LDPE-g-MMI 5 5
LDPE-MMI –ODDA 5-C10 LDPE LDPE-g-MMI 5 10
LDPE-MMI –ODDA 5-C15 LDPE LDPE-g-MMI 5 15
LDPE-MBI-ODDA 5-C5 LDPE LDPE-g-MBI 5 5
LDPE-MBI –ODDA 5-C10 LDPE LDPE-g-MBI 5 10
LDPE-MBI –ODDA 5-C15 LDPE LDPE-g-MBI 5 15
LDPE-IA-OODA 5-C5 LDPE LDPE-g-IA 5 5
LDPE-IA-OODA 5-C10 LDPE LDPE-g-IA 5 10
LDPE-IA-OODA 5-C15 LDPE LDPE-g-IA 5 15
LDPE-MMI-OODA 5-C5 LDPE LDPE-g-MMI 5 5
LDPE-MMI-OODA 5-C10 LDPE LDPE-g-MMI 5 10
LDPE-MMI-OODA 5-C15 LDPE LDPE-g-MMI 5 15
LDPE-MBI-OODA 5-C5 LDPE LDPE-g-MBI 5 5
LDPE-MBI-OODA 5-C10 LDPE LDPE-g-MBI 5 10
LDPE-MBI-OODA 5-C15 LDPE LDPE-g-MBI 5 15
60
Table 6.4: Sample description and contents of samples which contain LLDPE
Sample Description Polyolefine Compatiblizer Organoclay % Compatibilizer %
LLDPE-O0-C0 LLDPE --- 0 0 LLDPE-IA- O0-C5 LLDPE LLDPE-g-IA 0 5 LLDPE-IA- O0-C10 LLDPE LLDPE-g-IA 0 10 LLDPE-IA- O0-C15 LLDPE LLDPE-g-IA 0 15 LLDPE-MMI-O0-C5 LLDPE LLDPE-g-MMI 0 5 LLDPE-MMI-O0-C10 LLDPE LLDPE-g-MMI 0 10 LLDPE-MMI-O0-C15 LLDPE LLDPE-g-MMI 0 15 LLDPE-MBI-O0-C5 LLDPE LLDPE-g-MBI 0 5 LLDPE-MBI-O0-C10 LLDPE LLDPE-g-MBI 0 10 LLDPE-MBI-O0-C15 LLDPE LLDPE-g-MBI 0 15 LLDPE-OHDA 5-C0 LLDPE --- 5 0 LLDPE-OHDA 10-C0 LLDPE --- 10 0 LLDPE-OHDA 10-C0 LLDPE --- 15 0 LLDPE-ODDA 5-C0 LLDPE --- 5 0 LLDPE-ODDA 10-C0 LLDPE --- 10 0 LLDPE-ODDA 10-C0 LLDPE --- 15 0 LLDPE-OODA 5-C0 LLDPE --- 5 0 LLDPE-OODA 10-C0 LLDPE --- 10 0 LLDPE-OODA 10-C0 LLDPE --- 15 0 LLDPE-IA-OHDA 5-C5 LLDPE LLDPE-g-IA 5 5
LLDPE-IA-OHDA 5-C10 LLDPE LLDPE-g-IA 5 10
LLDPE-IA-OHDA 5-C15 LLDPE LLDPE-g-IA 5 15
LLDPE-MMI-OHDA 5-C5 LLDPE LLDPE-g-MMI 5 5
LLDPE-MMI -OHDA 5-C10 LLDPE LLDPE-g-MMI 5 10
LLDPE-MMI -OHDA 5-C15 LLDPE LLDPE-g-MMI 5 15
LLDPE-MBI-OHDA 5-C5 LLDPE LLDPE-g-MBI 5 5
LLDPE-MBI -OHDA 5-C10 LLDPE LLDPE-g-MBI 5 10
LLDPE-MBI -OHDA 5-C15 LLDPE LLDPE-g-MBI 5 15
LLDPE-IA-ODDA 5-C5 LLDPE LLDPE-g-IA 5 5
LLDPE-IA-ODDA 5-C10 LLDPE LLDPE-g-IA 5 10
LLDPE-IA-ODDA 5-C15 LLDPE LLDPE-g-IA 5 15
LLDPE-MMI-ODDA 5-C5 LLDPE LLDPE-g-MMI 5 5
LLDPE-MMI -ODDA 5-C10 LLDPE LLDPE-g-MMI 5 10
61
LLDPE-MMI -ODDA 5-C15 LLDPE LLDPE-g-MMI 5 15
LLDPE-MBI-ODDA 5-C5 LLDPE LLDPE-g-MBI 5 5
LLDPE-MBI -ODDA 5-C10 LLDPE LLDPE-g-MBI 5 10
LLDPE-MBI -ODDA 5-C15 LLDPE LLDPE-g-MBI 5 15
LLDPE-IA-OODA 5-C5 LLDPE LLDPE-g-IA 5 5
LLDPE-IA-OODA 5-C10 LLDPE LLDPE-g-IA 5 10
LLDPE-IA-OODA 5-C15 LLDPE LLDPE-g-IA 5 15
LLDPE-MMI-OODA 5-C5 LLDPE LLDPE-g-MMI 5 5
LLDPE-MMI-OCODA 5-C10 LLDPE LLDPE-g-MMI 5 10
LLDPE-MMI-OODA 5-C15 LLDPE LLDPE-g-MMI 5 15
LLDPE-MBI -OODA 5-C5 LLDPE LLDPE-g-MBI 5 5
LLDPE-MBI -OODA 5-C10 LLDPE LLDPE-g-MBI 5 10
LLDPE-MBI -OODA 5-C15 LLDPE LLDPE-g-MBI 5 15
Table 6.5: XRD measurement results of LDPE containing samples
Sample Description 2Ө d001 (Å)
Nanofil 757 7.19 12.3
ODDA 3.32 26.6
OHDA 2.95 29.9
OODA 2.80 31.5
LDPE-ODDA 5-C0 3,10 28,5
LDPE-OHDA 5-C0 2.55 34.7
LDPE-OODA 5-C0 2,52 35,0
LDPE-IA-ODDA 5-C5 3,41 25,9
LDPE-IA-ODDA 5-C10 3,38 26,1
LDPE-IA-ODDA 5-C15 3,18 27,8
LDPE-IA-OHDA 5-C5 2.43 36.4
LDPE-IA-OHDA 5-C10 < 2 ---
62
LDPE-IA-OHDA 5-C15 < 2 ---
LDPE-IA-OODA 5-C5 2,58 34,2
LDPE-IA-OODA 5-C10 2,57 34,3
LDPE-IA-OODA 5-C15 2,54 34,8
LDPE-MMI-ODDA 5-C5 3,44 25,7
LDPE-MMI -ODDA 5-C10 3,19 27,7
LDPE-MMI -ODDA 5-C15 2,44 36,2
LDPE-MMI-OHDA 5-C5 2.55 34.7
LDPE-MMI -OHDA 5-C10 2.38 37.1
LDPE-MMI -OHDA 5-C15 < 2 ---
LDPE-MMI-OODA 5-C5 2,57 34,3
LDPE-MMI -OODA 5-C10 2,50 35,3
LDPE-MMI -OODA 5-C15 2,46 35,9
LDPE-MBI-ODDA 5-C5 3,28 26,9
LDPE-MBI -ODDA 5-C10 3,26 27,1
LDPE-MBI -ODDA 5-C15 3,22 27,4
LDPE-MBI-OODA 5-C5 3,36 26,3
LDPE-MBI -OODA 5-C10 2,68 32,9
LDPE-MBI -OODA 5-C15 2,13 41,4
63
Table 6.6: XRD measurement results of LLDPE containing samples
Sample Desription 2Ө d001 (Å)
Nanofil 757 7.19 12.3
ODDA 3.32 26.6
OHDA 2.95 29.9
OODA 2.80 31.5
LLDPE-ODDA 5-C0 2.86 30.9
LLDPE-OHDA 5-C0 2.59 34.1
LLDPE-OODA 5-C0 2.58 34.2
LLDPE-IA-ODDA 5-C5 3.18 27.8
LLDPE-IA-ODDA 5-C10 3.07 28.7
LLDPE-IA-ODDA 5-C15 2.80 31.5
LLDPE-IA-OHDA 5-C5 2.67 33.0
LLDPE-IA-OHDA 5-C10 2.67 33.0
LLDPE-IA-OHDA 5-C15 2.55 34.7
LLDPE-IA-OODA 5-C5 2.64 33.4
LLDPE-IA-OODA 5-C10 2.60 34.0
LLDPE-IA-OODA 5-C15 < 2 ----
LLDPE-MMI-ODDA 5-C5 3.11 28.4
LLDPE-MMI-ODDA 5-C10 3.11 28.4
LLDPE-MMI-ODDA 5-C15 2.98 29.6
LLDPE-MMI-OHDA 5-C5 2.74 32.2
LLDPE-MMI-OHDA 5-C10 2.50 35.3
LLDPE-MMI-OHDA 5-C15 2.32 38.0
64
LLDPE-MMI-OODA 5-C5 2.59 34.1
LLDPE-MMI-OODA 5-C10 2.58 34.2
LLDPE-MMI-OODA 5-C15 2.34 37.7
LLDPE-MBI-ODDA 5-C5 3,01 29,3
LLDPE-MBI-ODDA 5-C10 2,82 31,3
LLDPE-MBI-ODDA 5-C15 <2 ---
LLDPE-MBI-OHDA 5-C5 2,70 32,7
LLDPE-MBI-OHDA 5-C10 2,66 43,1
LLDPE-MBI-OHDA 5-C15 2,49 46,0
LLDPE-MBI-OODA 5-C5 2,62 33,7
LLDPE-MBI-OODA 5-C10 2,56 34,5
LLDPE-MBI-OODA 5-C15 2,32 38,0
Table 6.7: Mechanical measurements of LDPE including samples
Sample Description Elongation at break(%)
Stres at break. (MPa)
%1 Secant modulus (MPa)
W at Break
(J) LDPE-O0-C0 573.4 7.40 167.0 3.7
LDPE-ODDA 5-C0 550.4 9.73 187.4 4.8
LDPE-OHDA 5-C0 542.4 10.23 190.3 5.1
LDPE-OODA 5-C0 530.2 10.27 190.7 4.9
LDPE-IA-ODDA 5-C5 602.5 10.84 170.0 5.9
LDPE-IA-ODDA 5-C10 661.3 13.34 284.5 7.8
LDPE-IA-ODDA 5-C15 707.2 14.46 290.5 8.5
LDPE- MMI-ODDA 5-C5 592.8 10.79 242.3 5.3
LDPE- MMI-ODDA 5-C10 636.5 13.23 295.0 6.3
LDPE- MMI-ODDA 5-C15 677.4 14.35 343.8 7.8
LDPE- MBI-ODDA 5-C5 591.5 10.71 230.0 5.3
LDPE- MBI-ODDA 5-C10 612.7 12.76 328.4 5.7
65
LDPE- MBI-ODDA 5-C15 654.1 13.67 342.0 7.4
LDPE-IA-OHDA 5-C5 628.9 12.33 327.5 5.6
LDPE-IA-OHDA 5-C10 685.5 15.52 393.3 8.8
LDPE-IA-OHDA 5-C15 734.9 16.63 490.0 10.1
LDPE- MMI-OHDA 5-C5 621.1 12.17 297.6 5.6
LDPE- MMI-OHDA 5-C10 676.8 14.18 355.3 7.7
LDPE- MMI-OHDA 5-C15 727.3 16.58 465.0 10.2
LDPE- MBI-OHDA 5-C5 614.5 11.95 266.4 5.4
LDPE- MBI-OHDA 5-C10 674.7 13.32 347.6 5.7
LDPE- MBI-OHDA 5-C15 715.4 15.42 416.6 9.2
LDPE-IA-OODA 5-C5 608.9 12.18 283.3 5.4
LDPE-IA-OODA 5-C10 670.1 13.87 340.0 7.1
LDPE-IA-OODA 5-C15 720.4 15.07 378.3 8.1
LDPE- MMI-OODA 5-C5 606.1 11.89 253.3 4.9
LDPE- MMI-OODA 5-C10 658.5 13.63 298.0 6.4
LDPE- MMI-OCODA 5-C15 708.5 14.76 345.0 7.7
LDPE- MBI -OODA 5-C5 603.1 11.17 212.5 5.8
LDPE- MBI -OODA 5-C10 647.8 13.39 281.6 6.7
LDPE- MBI -OODA 5-C15 685.8 14.52 333.3 7.5
Table 6.8: Mechanical measurements of LLDPE including samples
Sample Description Elongation at break(%)
Stress at break. (MPa)
%1 Secant modulus (MPa)
W at Break (J)
LLDPE 690.4 12.7 215.0 5.5
LLDPE-ODDA 5 658.5 15.3 315.0 6.5
LLDPE-OHDA 5 650.0 16.1 304.0 6.4
LLDPE-OODA 5 643.2 15.8 308.0 6.3
LLDPE-IA-ODDA 5-C5 702.0 19.2 310.0 9.0
LLDPE-IA-ODDA 5-C10 793.5 20.8 375 10.1
LLDPE-IA-ODDA 5-C15 844.1 21.8 400 11.5
LLDPE-MMI-ODDA 5-C5 719.0 19.7 295 8.5
LLDPE-MMI-ODDA 5-C10 851.2 21.7 340 10.7
LLDPE-MMI-ODDA 5-C15 905.1 23.5 390 11.2
LLDPE-MBI-ODDA 5-C5 696.7 17.55 298.0 7.2
LLDPE-MBI-ODDA 5-C10 736.5 19.77 365.0 9.6
66
LLDPE-MBI-ODDA 5-C15 781.2 23.28 395.9 10.9
LLDPE-IA-OHDA 5-C5 722.8 20.36 320.0 8.5
LLDPE-IA-OHDA 5-C10 808.2 22.44 368.0 10.5
LLDPE-IA-OHDA 5-C15 861.8 24.71 400.0 12.8
LLDPE-MMI-OHDA 5-C5 720.9 19.21 305.4 8.1
LLDPE-MMI-OHDA 5-C10 805.4 20.30 358 9.2
LLDPE-MMI-OHDA 5-C15 856.0 23.83 395.0 11
LLDPE-MBI-OHDA 5-C5 711.4 18.53 307.6 8.6
LLDPE-MBI-OHDA 5-C10 800.4 21.84 352.4 10.7
LLDPE-MBI-OHDA 5-C15 852.4 23.67 390.3 12.9
LLDPE-IA-OODA 5-C5 753.7 19.8 266 9.4
LLDPE-IA-OODA 5-C10 862.7 22.9 387 13.4
LLDPE-IA-OODA 5-C15 932.4 25.0 518 15.7
LLDPE-MMI-OODA 5-C5 719.2 19.4 266 8.7
LLDPE-MMI-OODA 5-C10 853.4 21.6 350 11.3
LLDPE-MMI-OODA 5-C15 922.5 24.4 520 14.8
LLDPE-MBI-OODA 5-C5 704.7 19.36 245 7.7
LLDPE-MBI-OODA 5-C10 801.8 20.98 375.0 10.1
LLDPE-MBI-OODA 5-C15 847.7 23.67 433.3 11.7
Table 6.9. Shore-D hardness measurement results of the PNC samples
Sample Description First Measurement
Second Measurement (After 20 sec.)
LDPE-OHDA 0-C0 44 34
LDPE-OHDA 5-C0 47 36
LDPE-IA-OHDA 5-C5 47 39
LDPE-IA-OHDA 5-C10 46 34
LDPE-IA-OHDA 5-C15 43 32
LDPE- MMI OHDA 5-C5 49 39
LDPE- MMI -OHDA 5-C10 48 38
LDPE- MMI -OHDA 5-C15 46 37
LLDPE-OHDA 0-C0 40 31
LLDPE-OHDA 5-C0 44 32
LLDPE -IA-OHDA 5-C5 46 38
67
LLDPE -IA-OHDA 5-C10 45 35
LLDPE -IA-OHDA 5-C15 44 34
LLDPE - MMI -OHDA 5-C5 46 35
LLDPE - MMI -OHDA 5-C10 43 33
LLDPE - MMI -OHDA 5-C15 42 31
Table 6.10: MFR, MVR, n-MFR and n-MVR values of all samples and control units
Sample Description MFR (g/10 min.) n-MFR MVR(cm3/10min.) n-MVR
LDPE-O0-C0 0.29 ------------- 0.30 -------------
LDPE-IA-O0-C5 0.27 ------------- 0.29 -------------
LDPE-IA-O0-C10 0.25 ------------- 0.28 -------------
LDPE-IA-O0-C15 0.23 ------------- 0.25 -------------
LDPE-MMI-O 0-C5 0.28 ------------- 0.29 -------------
LDPE-MMI -O0-C10 0.27 ------------- 0.27 -------------
LDPE-MMI –O 0-C15 0.24 ------------- 0.26 -------------
LDPE-MBI-O 0-C5 0.32 ------------- 0.35 -------------
LDPE-MBI -O0-C10 0.32 ------------- 0.34 -------------
LDPE-MBI –O 0-C15 0.32 ------------- 0.34 -------------
LDPE-IA-ODDA 5-C5 0.36 1.33 0.40 1.38
LDPE-IA-ODDA 5-C10 0.35 1.39 0.38 1.38
LDPE-IA-ODDA 5-C15 0.34 1.45 0.36 1.42
LDPE-MMI-ODDA 5-C5 0.34 1.21 0.37 1.30
LDPE-MMI-ODDA 5-C10 0.32 1.21 0.36 1.33
LDPE-MMI-ODDA 5-C15 0.31 1.31 0.36 1.36
LDPE-MBI-ODDA 5-C5 0.31 1.12 0.35 1.17
LDPE-MBI-ODDA 5-C10 0.32 1.14 0.33 1.15
LDPE-MBI-ODDA 5-C15 0.29 1.15 0.32 1.15
LDPE-IA-OODA 5-C5 0.35 1.29 0.36 1.25
LDPE-IA-OODA 5-C10 0.33 1.31 0.36 1.29
LDPE-IA-OODA 5-C15 0.31 1.36 0.34 1.35
LDPE-MMI-OODA 5-C5 0.35 1.26 0.37 1.29
LDPE-MMI-OODA 5-C10 0.35 1.30 0.36 1.33
68
LDPE-MMI-OODA 5-C15 0.33 1.39 0.35 1.35
LDPE-MBI-OODA 5-C5 0.33 1.15 0.35 1.19
LDPE-MBI-OODA 5-C10 0.32 1.16 0.34 1.20
LDPE-MBI-OODA 5-C15 0.33 1.29 0.37 1.33
LLDPE-O0-C0 1.97 ------------- 2.17 -------------
LLDPE-IA-O0-C5 1.61 ------------- 1.99 -------------
LLDPE-IA-O 0-C10 1.74 ------------- 1.63 -------------
LLDPE-IA-O0-C15 1.13 ------------- 1.36 -------------
LLDPE-MMI -O0-C5 1.32 ------------- 1.67 -------------
LLDPE-MMI -O0-C10 1.19 ------------- 1.41 -------------
LLDPE-MMI -O0-C15 1.13 ------------- 1.33 -------------
LLDPE-MBI -O0-C5 1.75 ------------- 1.76 -------------
LLDPE-MBI -O0-C10 1.80 ------------- 1.81 -------------
LLDPE-MBI –O0-C15 1.81 ------------- 1.82 -------------
LLDPE-IA-ODDA 5-C5 1.84 1.15 2.01 1.01
LLDPE-IA-ODDA 5-C10 1.79 1.53 1.87 1.15
LLDPE-IA-ODDA 5-C15 1.74 1.54 1.80 1.32
LLDPE-MMI-ODDA 5-C5 1.95 1.47 2.53 1.51
LLDPE-MMI-ODDA 5-C10 1.90 1.60 2.29 1.62
LLDPE-MMI-ODDA 5-C15 1.85 1.63 2.21 1.66
LLDPE-MBI-ODDA 5-C5 1.78 1.37 1.92 1.21
LLDPE-MBI-ODDA 5-C10 1.69 1.43 1.67 1.21
LLDPE-MBI-ODDA 5-C15 1.68 1.50 1.66 1.27
LLDPE-IA-OODA 5-C5 1.87 1.16 2.02 1.02
LLDPE-IA-OODA 5-C10 1.84 1.56 1.92 1.18
LLDPE-IA-OODA 5-C15 1.82 1.60 1.91 1.40
LLDPE-MMI-OODA 5-C5 1.88 1.42 1.96 1.17
LLDPE-MMI-OODA 5-C10 1.80 1.52 1.92 1.36
LLDPE-MMI-OODA 5-C15 1.73 1.53 1.75 1.31
LLDPE-MBI-OODA 5-C5 1.81 1.39 1.92 1.20
LLDPE-MBI-OODA 5-C10 1.76 1.48 1.78 1.28
LLDPE-MBI-OODA 5-C15 1.70 1.52 1.70 1.30
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Figure 6.1: XRD pattern of Nanofil 757
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Figure 6.2: XRD patterns of some polymer nanocomposite samples that contains LDPE as matrix and MMI in compatibilizer.
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Figure 6.3: XRD patterns of some polymer nanocomposite samples that contains LLDPE as matrix and MMI in compatibilizer.
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Figure 6.4: XRD patterns of some polymer nanocomposite samples that contains LLDPE as matrix and IA in compatibilizer.
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BIOGRAPHY
He was born 1981 in Istanbul. He graduated from Yunus Emre High School in 1999
and attempted to Chemistry Department of Istanbul university in the same year.
In 2004 he graduated from university. He was accepted as a master student to
Istanbul Technical University, Polymer Science and Technology Interdisciplinary
graduate Programme and he is still completing her master education.
