Research Article Effect of Coupling Agent on the Properties of …downloads.hindawi.com/archive/2014/412432.pdf · 2019. 7. 31. · DPMI content (g/g composite) (a) Izod impact (J/m)

Research ArticleEffect of Coupling Agent on the Properties ofPolymerDate Pits Composites

Fares D Alsewailem and Yazeed A Binkhder

Petrochemicals Research Institute King Abdulaziz City for Science and Technology PO Box 6086 Riyadh 11442 Saudi Arabia

Correspondence should be addressed to Fares D Alsewailem fsewailmkacstedusa

Received 7 October 2013 Accepted 17 December 2013 Published 9 January 2014

Academic Editor Nikhil Gupta

Copyright copy 2014 F D Alsewailem and Y A Binkhder This is an open access article distributed under the Creative CommonsAttribution License which permits unrestricted use distribution and reproduction in any medium provided the original work isproperly cited

The morphology of the fracture surfaces of polymerdate pits composites was investigated Polymers used in this study were highdensity polyethylene (HDPE) and polystyrene (PS) Date pits in the form of granules were two types of date pits khlaas (K) andsekari (S) Two coupling agents diphenylmethane-4 41015840-diisocyanate (DPMI) and ethylene propylene grafted withmalice anhydride(EP-g-MA) were used to ease the incorporation of date pit particles into polymer matrix The SEM micrographs of the neatcomposites that is with no coupling agents showed coarse morphology with bad dispersion adhesion and distribution of datepit particles within the polymer matrix On the other hand PS100K composites coupled with DPMI and EP-g-MA had reasonabledispersed phase size with good distribution and adhesion to the composite matrix which in turn improve themechanical propertiesof the resulted polymerdate pits composites

1 Introduction

Biomass in the form of agricultural waste such as wheat strawcorncob and rice husk offers feasible and environmentallybenign filling materials for polymeric materials One ofthese biofillers which is abundantly available in the Arabianpeninsula is date pits a byproduct of palm trees (Phoenixdactylifera L) One date pit may contain up to 10 oilsminerals (eg potassium) and fibers (gt64)

Incorporating a cost-effective filler in a polymeric matrixwill only be feasible if it does not drastically alter thematrix main characteristics such as mechanical propertiesThe determinant issue here is the compatibility betweenthe interfaces of a biofiller and the polymer matrix Thisis important in order to have property-stable compositesystem For this reason various compatibilizers or cou-pling agents were suggested by some studies in the past toformulate efficient biocomposites based on polymer matri-ces [1ndash4] Wang et al [1] have shown that incorporatingDPMI as a coupling agent for the composites of wheatstrawpolyethylene (PE) increased its modulus significantlyWood fiberpolypropylene composites with goodmechanical

properties may be obtained by using modified couplingagent containing isocyanate functional group [4] Maleatedpolyolefins such as m-PE and polypropylene (m-PP) werefound efficient compatibilizers for improving mechanicalproperties of PE and PP filled with wood fibers [2 3]

Studies on polymerdate pits composites are sparse [5 6]In our previous study [5] we reported the formulation ofthe noncompatibilized polymerdate pits composites basedon high density polyethylene (HDPE) and polystyrene (PS)We concluded that while tensile strength (TS) of the polymerdate pits especially that of HDPEdate pits composites wasnot greatly affected by the presence of date pit particlesthe Izod impact strength (IIS) of such composite systemdeteriorated to greater extent upon the incorporating of datepit particles into the polymer matrix We emphasized thatthis can be attributed to the weakness of the interface ofthe composites due to the lack of proper compatibility thatis the presence of suitable coupling agent Therefore theaim of the current study was to investigate the influence ofsome coupling agents on the properties of polymerdate pitscomposites

Hindawi Publishing CorporationJournal of CompositesVolume 2014 Article ID 412432 7 pageshttpdxdoiorg1011552014412432

2 Journal of Composites

Khlaas (K) Sekari (S)

(a) (b)

Figure 1 Photograph of date pits used in this study (a) Khlaas and (b) sekari

minus07

minus06

minus05

minus04

minus03

minus02

minus01

0

01

02

7 44 81 118 155 192 229 266 303 340

Temperature (∘C)

Hea

t flow

(Wg

)

KS

HDPEPS100

minus30

Figure 2 DSC scans for all neat materials

2 Experimental

21 Materials Used

211 Date Pits Two locally grown date pitsmdashkhlaas (K) andsekari (S)mdashwere used in this study A photograph of thesetwo date pits is shown in Figure 1 A khlaas date pit has higherpercentages of aluminum and calcium than those found in asekari date pit [7] On the other hand some other mineralssuch as magnesium and potassium may be found at highcontents in sekari date pits but not in khlaas date pits [7]

212 Matrix Materials Polymers used in this study werea blow molding grade HDPE and a general purposepolystyrene PS100 with melt flow index (MFI) that equals13 g10min These two polymers are courtesy of Saudi BasicIndustries Corporation (SABIC) in Riyadh Saudi Arabia

213 Coupling Agents Two coupling materials were usedas follows The first was diphenylmethane-4 41015840-diisocyanate(DPMI) as used before for agrowastepolymer composites [1]The second coupling material was ethylene propylene graftedwith maleic anhydride (EP-g-MA Exxelor VA 1803) with aglass transition temperature Tg of minus57∘C

22 Procedure

221 Preparing Date Pits Khlaas and sekari date pits wereground to a particle size of 015mm as described in ourprevious study [5]

222 Preparing Polymer-Date Pits Composites Preparationof HDPE and PS100 with K and S date pits was given else-where [5] DPMI and EP-g-MA were added to the PS100K(7030) wt at up to 5 g and 1 g respectively per 100 and6 grams of the neat composite (ie 30 wt KPS100) Theblends were melt mixed for 10min and then injected into amold for making tensile and impact samples according to thedimensions of ASTM D 1708 and ASTM D 256 respectively

223 Mechanical Testing Tensile strength and Izod impactstrength in accordance with ASTM D 1708 and ASTM D256 respectively were conducted to assess the mechanicalstiffness and toughness of the prepared date pitsHDPE andPS100 composites Tinius Olsen pendulum impact tester (IT504) with a total capacity of energy that equals 7 J was usedto measure notched Izod impact strength of the polymerdate pits composites Automatic notcher equipped with avery sharp blade that can provide a notch in accordancewith ASTM D 265 was used to notch the sample barsTensile strength measurements were carried out by using aHounsfield universal testing machine model H5KS using5KN load cell

Journal of Composites 3

(a) (b)

(c) (d)

Figure 3 SEMmicrographs of the fracture surfaces of the Izod samples for the composites at 30wt date pits loading Images were taken atlow magnification (gt100x) (a) HDPEK (b) HDPES (c) PS100K and (d) PS100S

224 Thermal Testing A differential scanning calorimetryDSC (type TA-Q10) was used to study the thermal behaviorof date pits and neat polymer Samples ranging from 10 to15mg of the composites with various loadings of date pitswere heated twice up to 200∘C at a heating rate of 10∘CminIn addition neat polymers anddate pitswere tested separatelyby DSC at a temperature range of minus30 to 340∘C

225 Morphology of the Composites The fracture surfaces ofthe Izod samples were examined by the scanning electronmicroscope SEM (FEI model NNL 200) and the scanningprobe microscope SPM (NT-MDT solver next NSGO1-Aseries)

3 Results and Discussion

Figure 2 shows the DSC scans for the neat polymers HDPEand PS100 and the two types of date pits K and S used inthis study The melt peak of HDPE is not completely shownbecause we wanted to clearly show the transitions and peaksof other materials that is PS100 K and S Both date pitsK and S exhibited similar thermal behavior with distinct

endothermic peak at approximately 0∘C probably due to oilor water crystals melting [8] and a broad endothermic peakat onset and peak maximum of 85∘C and 130∘C respectivelyFinally there is a distinctive exothermic peak in the rangefrom 290∘C to 320∘C

The morphology of the fracture surfaces of the Izodspecimens of the composites was examined and represen-tative SEM micrographs are given in Figures 3ndash6 Figure 3shows that even at very lowmagnification (100ndash130x) of SEMimaging the date pits domain appeared as a large chunk withirregular shape morphology Figure 4 shows the morphologyof the fracture surfaces of the HDPEK composites at 1020 and 30wt date pits In Figure 4 one can see the pooradhesion between date pits K particles and HDPE matrix Itmust be recalled here that HDPE is a very toughmaterial thatis unbreakable in a notched IIS and despite this fact we haveseen how a small quantity 5 wt of date pits pronouncedlyreduced its toughness [5] Cavitations as a response to energyabsorption to break thematerial were clearly seen in Figure 4however in the absence of compatibility between HDPE anddate pits particles as date pits particles were debonded out ofHDPE matrix a weak interface was created and led to lowertoughness Figure 5 gives the morphology of the fractured


(a)

(b)

(c)

Figure 4 SEM micrographs of the fracture surfaces of the Izodsamples for the HDPEK composites at various loadings of date pits(a) 10 wt (b) 20wt and (c) 30wt

Izod samples of HDPES composites which seemed differentfrom that observed with HDPEK Here in Figure 5 date pitssize appears smaller and regular despite the debonding ofsome particles as shown in Figure 5(c)Thismight explain theimprovement in IIS for HDPES composites in contrast withthat of the HDPEK composites as reported by our previous

(a)

(b)

(c)

Figure 5 SEM micrographs of the fracture surfaces of the Izodsamples for the HDPES composites at various loadings of date pits(a) 10 wt (b) 20wt and (c) 30wt

study [5] Seeking a plausible explanation for the reductionin IIS for the PS100date pits composites [5] representativemicrofracture surfaces of the Izod specimens of PS100S andPS100K loaded with 30wt of date pits shown in Figure 6were investigated We can see that although the adhesionbetween the dispersed phase that is date pits and thematrixthat is PS100 seems to be visually good the reduction in theIIS values occurred [5] We believe that the reason for thisreduction may be rooted to the bad distribution and largedomain size of date pits within the polymer matrix as clearlyseen in Figure 6


(a) (b)

Figure 6 SEMmicrographs of the fracture surfaces of the Izod samples for the PS100 composites at 30wt loading of date pits (a) PS100Kand (b) PS100S

0

5

10

15

20

25

30

0 1100 5100

Stre

ngth

DPMI content (gg composite)

(a)

Izod impact (Jm)Tensile (Mpa)

0

5

10

15

20

25

30

35

40

45

0 110 16

EP-g-MA content (gg composite)

Stre

ngth

(b)

Figure 7 Strength of the PS100 with 30wt K date pits with two coupling agents (a) DPMI and (b) EP-g-MA

Polystyrene has very low toughness that is resiliencein comparison with that of the polyethylene Furthermorethe resilience of the polystyrene is anticipated to deteriorateupon incorporating additives and fillers as this was alreadyshown by our previous study [5] For this reason we choseto use PS100date pits composite system to show the effectof coupling agents on altering the morphology of the frac-ture surfaces of the composites and hence the mechanicalproperties may be improved Figure 7 shows the strength ofthe PS100K (7030wt) composites in the presence of twocoupling agents DPMI and EP-g-MA Figure 7(a) shows thatDPMI at a concentration of 5 g per 100 g of neat compositeslightly increases the IIS of the composites while a smalldecrease in the TS of the composites was observed On theother hand small amounts of EP-g-MA for example 1 gper 10 g of the neat composite have led to a remarkable

increase in IIS as shown in Figure 7(b) Nevertheless TSof the composite was reduced to 50 upon the addition ofup to 1 g of EP-g-MA per 6 g of neat composites This isexpected since rubbers and elastomers have very low valuesof modulusThis finding may be put in the frame of structureor morphology-property relationships In other words oneshould link the properties to the appearance and distributionof the dispersed phase in the composite matrix Figure 8shows a comparison of the fracture surface morphologies ofthe neat composite that is PS100K (7030wt) with thatof the same composite but in the presence of DPMI andEP-g-MA One can clearly see from Figures 8(a) and 9(a)that the K particles appear large and badly distributed withinthe PS100 matrix In contrast Figures 8(b) and 9(b) showthe fine distribution of smaller K particles within the PS100matrix upon coupling with small amount of DPMI Lastly


(a)

(b)

(c)

Figure 8 SEM micrographs of PS100K (7030wt) with (a) 0coupling agent (b) 130 diphenylmethane (PSK) (c) 16 EP-g-MA(PSK)

Figure 8(c) shows different morphology in comparison withthat of the neat composite where the dispersed domainsappeared smaller and rubber phase appears as elongatedparticles with a good sign of adhesion into the compositematrix which explains the improvement on the resilience ofthe composites as shown in Figure 7(b)

4 Conclusion

Polymerdate pits composites modified with two couplingagent systems that is DPMI and EP-g-MA were prepared

10 2 3 4 5 6 7

1

2

3

4

5

6

7

0

(120583m)

(120583m

)

(a)

10 2 3 4 5 6

1

2

3

4

5

6

0

(120583m)

(120583m

)

(b)

Figure 9 SPMmicrographs for PS100K (7030wt) coupled withDPMI (a) 0 and (b) 5100 (g DPMIg neat composite)

and tested mechanically and morphologically Polymericmatrices used were HDPE and PS In the absence of propercoupling agent systems fracture surfaces of the polymerdatepits composite systems tested in this study were rough withgreat degree of debonding and bad adhesion of date pit parti-cles which appeared to be very large Both coupling agentsused in this study DPMI and EP-g-MA were effective inaltering the morphology of the polymerdate pits compositesand hence improving the mechanical properties


Conflict of Interests

The authors declare that there is no conflict of interests re-garding the publication of this paper

Acknowledgment

The authors thank king Abdulaziz City for Science and Tech-nology (KACST) for supporting the study

References

[1] Z Wang E Wang S Zhang Z Wang and Y Ren ldquoEffects ofcross-linking on mechanical and physical properties of agricul-tural residuesrecycled thermoplastics compositesrdquo IndustrialCrops and Products vol 29 no 1 pp 133ndash138 2009

[2] H-S Yang H-J Kim H-J Park B-J Lee and T-S HwangldquoEffect of compatibilizing agents on rice-husk flour reinforcedpolypropylene compositesrdquo Composite Structures vol 77 no 1pp 45ndash55 2007

[3] Y Lei Q Wu F Yao and Y Xu ldquoPreparation and properties ofrecycledHDPEnatural fiber compositesrdquoComposites A vol 38no 7 pp 1664ndash1674 2007

[4] A Karmarkar S S Chauhan J M Modak and M ChandaldquoMechanical properties of wood-fiber reinforced polypropylenecomposites effect of a novel compatibilizer with isocyanatefunctional grouprdquo Composites A vol 38 no 2 pp 227ndash2332007

[5] F D Alsewailem and Y A Binkhder ldquoPreparation and char-acterization of polymerdate pits compositesrdquo Journal of Rein-forced Plastics and Composites vol 29 no 11 pp 1743ndash17492010

[6] AGhazanfari S Emami S Panigrahi and LG Tabil ldquoThermaland mechanical properties of blends and composites fromHDPE and date pits particlesrdquo Journal of Composite Materialsvol 42 no 1 pp 77ndash89 2008

[7] J S Mossa M S Hifnawy and A G Mekkawi ldquoPhotochemicaland biological investigation on date seeds (Phoenix dactyliferaL) produced in Saudi Arabiardquo Arab Gulf Journal of Science andResearch vol 4 no 2 pp 495ndash507 1986

[8] M S Rahman S KasapisN S ZAl-Kharusi IMAl-Marhubiand A J Khan ldquoComposition characterisation and thermaltransition of date pits powdersrdquo Journal of Food Engineering vol80 no 1 pp 1ndash10 2007

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of



CeramicsJournal of


CompositesJournal of

NanoparticlesJournal of



International Journal of

Biomaterials


NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014


CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research



MetallurgyJournal of


BioMed Research International

MaterialsJournal of


Nano

materials


Journal ofNanomaterials


Khlaas (K) Sekari (S)

(a) (b)

Figure 1 Photograph of date pits used in this study (a) Khlaas and (b) sekari

minus07

minus06

minus05

minus04

minus03

minus02

minus01

0

01

02

7 44 81 118 155 192 229 266 303 340

Temperature (∘C)

Hea

t flow

(Wg

)

KS

HDPEPS100

minus30

Figure 2 DSC scans for all neat materials

2 Experimental

21 Materials Used

211 Date Pits Two locally grown date pitsmdashkhlaas (K) andsekari (S)mdashwere used in this study A photograph of thesetwo date pits is shown in Figure 1 A khlaas date pit has higherpercentages of aluminum and calcium than those found in asekari date pit [7] On the other hand some other mineralssuch as magnesium and potassium may be found at highcontents in sekari date pits but not in khlaas date pits [7]

212 Matrix Materials Polymers used in this study werea blow molding grade HDPE and a general purposepolystyrene PS100 with melt flow index (MFI) that equals13 g10min These two polymers are courtesy of Saudi BasicIndustries Corporation (SABIC) in Riyadh Saudi Arabia

213 Coupling Agents Two coupling materials were usedas follows The first was diphenylmethane-4 41015840-diisocyanate(DPMI) as used before for agrowastepolymer composites [1]The second coupling material was ethylene propylene graftedwith maleic anhydride (EP-g-MA Exxelor VA 1803) with aglass transition temperature Tg of minus57∘C

22 Procedure

221 Preparing Date Pits Khlaas and sekari date pits wereground to a particle size of 015mm as described in ourprevious study [5]

222 Preparing Polymer-Date Pits Composites Preparationof HDPE and PS100 with K and S date pits was given else-where [5] DPMI and EP-g-MA were added to the PS100K(7030) wt at up to 5 g and 1 g respectively per 100 and6 grams of the neat composite (ie 30 wt KPS100) Theblends were melt mixed for 10min and then injected into amold for making tensile and impact samples according to thedimensions of ASTM D 1708 and ASTM D 256 respectively

223 Mechanical Testing Tensile strength and Izod impactstrength in accordance with ASTM D 1708 and ASTM D256 respectively were conducted to assess the mechanicalstiffness and toughness of the prepared date pitsHDPE andPS100 composites Tinius Olsen pendulum impact tester (IT504) with a total capacity of energy that equals 7 J was usedto measure notched Izod impact strength of the polymerdate pits composites Automatic notcher equipped with avery sharp blade that can provide a notch in accordancewith ASTM D 265 was used to notch the sample barsTensile strength measurements were carried out by using aHounsfield universal testing machine model H5KS using5KN load cell


(a) (b)

(c) (d)









(a)

(b)

(c)



(a)

(b)

(c)




(a) (b)


0

5

10

15

20

25

30

0 1100 5100

Stre

ngth


(a)


0

5

10

15

20

25

30

35

40

45

0 110 16


Stre

ngth

(b)





(a)

(b)

(c)



4 Conclusion


10 2 3 4 5 6 7

1

2

3

4

5

6

7

0

(120583m)

(120583m

)

(a)

10 2 3 4 5 6

1

2

3

4

5

6

0

(120583m)

(120583m

)

(b)






Acknowledgment


References
















CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




(a) (b)

(c) (d)









(a)

(b)

(c)



(a)

(b)

(c)




(a) (b)


0

5

10

15

20

25

30

0 1100 5100

Stre

ngth


(a)


0

5

10

15

20

25

30

35

40

45

0 110 16


Stre

ngth

(b)





(a)

(b)

(c)



4 Conclusion


10 2 3 4 5 6 7

1

2

3

4

5

6

7

0

(120583m)

(120583m

)

(a)

10 2 3 4 5 6

1

2

3

4

5

6

0

(120583m)

(120583m

)

(b)






Acknowledgment


References
















CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




(a)

(b)

(c)



(a)

(b)

(c)




(a) (b)


0

5

10

15

20

25

30

0 1100 5100

Stre

ngth


(a)


0

5

10

15

20

25

30

35

40

45

0 110 16


Stre

ngth

(b)





(a)

(b)

(c)



4 Conclusion


10 2 3 4 5 6 7

1

2

3

4

5

6

7

0

(120583m)

(120583m

)

(a)

10 2 3 4 5 6

1

2

3

4

5

6

0

(120583m)

(120583m

)

(b)






Acknowledgment


References
















CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




(a) (b)


0

5

10

15

20

25

30

0 1100 5100

Stre

ngth


(a)


0

5

10

15

20

25

30

35

40

45

0 110 16


Stre

ngth

(b)





(a)

(b)

(c)



4 Conclusion


10 2 3 4 5 6 7

1

2

3

4

5

6

7

0

(120583m)

(120583m

)

(a)

10 2 3 4 5 6

1

2

3

4

5

6

0

(120583m)

(120583m

)

(b)






Acknowledgment


References
















CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




(a)

(b)

(c)



4 Conclusion


10 2 3 4 5 6 7

1

2

3

4

5

6

7

0

(120583m)

(120583m

)

(a)

10 2 3 4 5 6

1

2

3

4

5

6

0

(120583m)

(120583m

)

(b)






Acknowledgment


References
















CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials






Acknowledgment


References
















CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



Documents

Research Article Effect of Coupling Agent on the Properties of …downloads.hindawi.com/archive/2014/412432.pdf · 2019. 7. 31. · DPMI content (g/g composite) (a) Izod impact (J/m)