Preparation of Fully Cross-Linked CNBR/PP-g-GMA andCNBR/PP/PP-g-GMA Thermoplastic Elastomers and TheirMorphology, Structure and Properties

XIAODONG XU,1,2 JINLIANG QIAO,2 JINGHUA YIN,1 YING GAO,1 XIAOHONG ZHANG,2 YONGTAO DING,1

YIQUN LIU,2 ZHIRONG XIN,1 JIANMING GAO,2 FAN HUANG,2 ZHIHAI SONG2

1State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy ofSciences, Changchun 130022, China

2SINOPEC Beijing Research Institute of Chemical Industry, Beijing 100013, China

Received 24 April 2003; revised 6 August 2003; accepted 17 August 2003

ABSTRACT: Binary CNBR/PP-g-GMA and ternary CNBR/PP/PP-g-GMA thermoplasticelastomers were prepared by reactive blending carboxy nitrile rubber (CNBR) powderwith nanometer dimension and polypropylene functionalized with glycidyl methacry-late (PP-g-GMA). Morphology observation by using an atomic force microscope (AFM)and TEM revealed that the size of CNBR dispersed phase in CNBR/PP-g-GMA binaryblends was much smaller than that of the corresponding CNBR/PP binary blends.Thermal behavior of CNBR/PP-g-GMA and CNBR/PP blends was studied by DSC.Comparing with the plain PP-g-GMA, Tc of PP-g-GMA in CNBR/PP-g-GMA blendsincreased about 10 °C. Both thermodynamic and kinetic effects would influence thecrystallization behavior of PP-g-GMA in CNBR/PP-g-GMA blends. At a fixed content ofCNBR, the apparent viscosity of the blending system increased with increasing thecontent of PP-g-GMA. FTIR spectrum verified that the improvement of miscibility ofCNBR and PP-g-GMA was originated from the reaction between carboxy end groups ofCNBR and epoxy groups of GMA grafted onto PP molecular chains. Comparing withCNBR/PP blends, the tensile strength, stress at 100% strain, and elongation at breakof CNBR/PP-g-GMA blends were greatly improved. © 2004 Wiley Periodicals, Inc. J PolymSci Part B: Polym Phys 42: 1042–1052, 2004Keywords: carboxy nitrile rubber; functionalized polypropylene; thermoplastic elas-tomer; morphology and structure

INTRODUCTION

During the last few decades the commercial im-portance of polymer blends has gradually in-creased, owing to the possibility of achieving de-sirable properties by simple blending of polymers.Among the different types of polymer blends ther-moplastic elastomers had their own advantages

as they combined the processability of plasticswith the performance of vulcanized rubbers.1,2

Thermoplastic elastomers prepared by blend-ing polypropylene or polyethylene with nitrilerubber have raised a lot of interests because ofthe combination of the oil-resistant property,the excellent mechanical property, and process-ing behavior.3–18 Due to the fact that nitrilerubber and polyolefin were immiscible thermo-dynamically, compatibilization was necessary,which could be performed by addition of somekinds of block or graft copolymers, or by in situ

Correspondence to: Jinghua Yin (E-mail: yinjh@ciac.jl.cn)Journal of Polymer Science: Part B: Polymer Physics, Vol. 42, 1042–1052 (2004)© 2004 Wiley Periodicals, Inc.

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formation of copolymers that contained blend-ing components.19

Coran et al.3 investigated the effect of the size ofrubber particles on mechanical properties of ther-moplastic elastomers. They indicated that the ulti-mate properties of thermoplastic elastomers wereinversely proportional to the size of rubber parti-cles. The minimum size of rubber particles obtainedby dynamic vulcanization method was usuallyabout 1–2 �m. Recently, a new blend consisting ofepoxy resin and a fully cured carboxy nitrile rubberpowder with nanometer scale (50–100 nm) was re-ported.20–22 The application of the rubber powderprovided a new strategy to reduce the size of rubberdomains and further improve the performance ofthermoplastic elastomers.

In this presentation, preparation of fully cross-linked CNBR/PP-g-GMA and CNBR/PP/PP-g-GMA thermoplastic elastomers was reported.Comparing with the traditional preparingmethod, following differences could be found.First, a fully cured carboxy nitrile rubber powderwith nanometer scale (50–100 nm) was adopted.Second, the traditional dynamic vulcanizationprocess of the rubber component during blendingprocess was eliminated. And third, polypropylenefunctionalized with glycidyl methacrylate (PP-g-GMA) was used to improve the compatibility be-tween CNBR and PP. The effects of blending ratioand reactive compatibilization on the morphol-ogy, structure, thermal properties, rheological be-havior, and mechanical properties of CNBR/PP-g-GMA and CNBR/PP/PP-g-GMA thermoplasticelastomers were investigated systematically.

EXPERIMENTAL

Materials

PP (PQR 01) with a MFR of 0.4 g/10 min wassupplied by Qilu Petrochemical Industrial Co.,China. It was a random copolymer with ethylenecontent of 4.8 mol. %, Mn � 1,55000, Mw� 7,78000, and Mw/Mn � 5.02.

Commercial GMA with density of 1.07 g/cm3

was purchased from Suzhou Anli Chemical Fac-tory, China and adopted as the grafting monomer.

Dicumyl peroxide (DCP) was supplied by Bei-jing Chemical Factory, China. It was re-crystal-lized before using to remove the absorbed water.

Fully cured CNBR powder (VP-501) with par-ticle size of 50–100 nm and gel content of 97.1%was offered by Beijing Research Institute ofChemical Industry, SINOPEC, China.

Preparation of PP-g-GMA

PP-g-GMA was prepared by using a homemadereactive co-rotating twin-screw extruder with adiameter of 30 mm and the ratio of length todiameter (L/D) of 44. GMA, DCP, and PP werepremixed in a rotating mixer and then added intothe hopper of the extruder. Reactive extrudingtemperature was about 190 °C.

Preparation of CNBR/PP, CNBR/PP-g-GMA andCNBR/PP/PP-g-GMA Blends

CNBR/PP, CNBR/PP-g-GMA and CNBR/PP/PP-g-GMA blends were prepared by blending fullycured CNBR powder with PP or PP-g-GMA, usinga ZSK-25 twin-screw extruder made by WP Com-pany, Germany. The blending temperature wascontrolled at 200 °C. CNBR/PP blends were de-signed as U100, U70, U60, U50, U40, U30, U25 andCNBR/PP-g-GMA blends were designed as C100,C70, C60, C50, C40, C30, C25, respectively. The sub-scripts following U and C indicated correspondingcontent (weight percentage) of PP and PP-g-GMA ineach blend. CNBR/PP/PP-g-GMA blends were de-signed as C40x. Here, the subscript 40 presented thetotal content (weight percentage) of PP and PP-g-GMA, and x presented the content of PP-g-GMA.

Test with FTIR Spectrometer

The possible reaction between carboxy groups ofCNBR and epoxy groups of PP-g-GMA was testedby using a BIO-RAD FTS-135 FTIR spectrometer.Its resolution was 4 cm�1 and the number ofscans was 16. Testing films were prepared byusing press molded method at about 200 °C. Beforetesting, PP-g-GMA was purified to remove the pos-sible GMA monomers and homo-polymers.23

Morphology Observation

The morphology of carboxy nitrile rubber powderwas examined by using a JSM-35C scanning elec-tron microscope (SEM). Before observation therubber powder was dispersed in ethanol by usingultrasonic and then dropped on a sample stage fordrying.

Morphology of CNBR/PP, CNBR/PP-g-GMAand CNBR/PP/PP-g-GMA blends were observedby using AFM (NanoScope IIIa atomic force mi-croscope, Digital Instrumental Company) and aHitachi H800 TEM. Before observation sampleswere microtomed at about �100 °C with a glass

CNBR/PP-g-GMA AND CNBR/PP/PP-g-GMA THERMOPLASTIC ELASTOMERS 1043

knife. Tapping mode was adopted as the imaginemode for AFM observation. Samples for TEM ob-servation were stained in the vapor of an aqueoussolution of OsO4 or RuO4.

The spherulitic structure of sample C100 andC70 was observed by using a Leica polarized opti-cal microscope (POM) equipped with a LinkamTM 600 hot stage. The isothermal crystallizationtemperature after eliminating the influence of thethermal history was 130 °C for C100 and 140 °C forC70, respectively.

Thermal Behavior

Thermal behavior of blending samples was inves-tigated by using a Perkin-Elmer DSC-7 differen-tial scanning calorimeter (DSC). All samples wereheated to 200 °C and held for 5 min to eliminatethe influence of the thermal history. A scanningrate of 10 °C/min was adopted. The weight of asample was about 4–7 mg.

Rheological Properties of Sample U40, C4004, andC4020

Rheological properties of sample U40, C4004, andC4020 were investigated by using a GOTTFERTcapillary rheometer at a testing temperature of190 °C. The length and diameter of the adoptedcapillary were 20 mm and 0.5 mm, respectively.End effects were neglected, but the Rabinowitschcorrection was applied.

Determination of Mechanical Properties

Tensile strength and elongation at break of theabove blending samples were determined by using atester (SHIMADZU AG-1, made in Japan), follow-ing ASTM D412-95. The adopted speed of the crosshead was 500 mm/min. The hardness of each sam-ple was determined following the ASTM D2240-97.And the swollen volume of each sample in gasolinewas determined following the ASTM D471-79.

RESULTS AND DISCUSSION

Reaction Between CNBR and PP-g-GMA

FTIR spectrum of CNBR was shown in Figure1(a). The broad peak at 2500 to 3500 cm�1 wasattributed to stretching vibration of OOH of car-boxy groups. And the shoulder peak appeared at1700 cm�1 was attributed to carbonyl stretching

vibration of OCOOH groups. These features re-vealed the existence of carboxy groups on CNBRmolecular chains.

FTIR spectrum of purified PP-g-GMA was shownin Figure 1(b). The peak at 899 cm�1, which wasattributed to asymmetric stretching vibration of ep-oxy group, could be seen. The other characteristicvibrating bands of epoxy groups were not found.This was due to the fact that these bands wereoverlapped by the vibrating bands of polypropylene.Moreover, the peak at 1740 cm�1 was attributed tocarbonyl stretching vibration of GMA in PP-g-GMA.These features revealed the fact that GMA wasgrafted onto PP molecular chains.

As shown in Figure 1(c), the peaks at 899 cm�1

and 1700 cm�1, which were attributed to stretchingvibration of epoxy groups and carboxy groups, re-spectively, disappeared in the corresponding FTIRspectra of the compatibilized CNBR/PP-g-GMAblend. Two new vibration peaks at 3498 cm�1 and1123 cm�1 which could be attributed to the stretch-ing vibration of OOH and OCOO(H) groups, re-spectively, were observed. These features suggestedthat the epoxy group of PP-g-GMA opened and re-acted with the carboxy group of CNBR to producean ester group and a hydroxy group. The possiblereaction could be tentatively expressed as following,as suggested in Mishra et al.24

Morphology of CNBR/PP and CNBR/PP-g-GMABlends

SEM micrograph of the fully cured CNBR powderis shown in Figure 2. It can be seen that the

Figure 1. FTIR spectra of (a) CNBR, (b) PP-g-GMA,and (c) CNBR/PP-g-GMA blend.

1044 XU ET AL.

diameter of CNBR particles was in the range of50–100 nm.

AFM micrographs of sample U40 and C40 areshown in Figure 3. The matrix (the white part) isPP or PP-g-GMA and the domains (the black part)is CNBR aggregates. In this study, since the fullycross-linked CNBR powder was directly blendedwith molten PP or PP-g-GMA in a twin-screwextruder without adding any vulcanizing agent,no further cross-linking of CNBR happened andno phase reversion occurred. And the final mor-phology of CNBR domains mainly depended uponthe size of the original CNBR droplets in latex21,22

and the possible aggregation of CNBR particlesduring blending process. As shown in Figure 3,the size of most rubber particles was larger than1 �m. It meant that in both blends, aggregation ofCNBR particles happened. But the size of CNBRaggregates (the black part) in sample C40 was muchsmaller and its distribution was more homogeneousthan that in the corresponding sample U40.

The above features could be tentatively ex-plained as that the improvement of compatibilitybetween CNBR and PP introduced the reduction ofthe size of CNBR particles. PP and CNBR wereincompatible thermodynamically, which would re-sult in high interfacial tension and poor interfacialadhesion between two phases. With the addition ofPP-g-GMA into the two blending components,chemical reactions between carboxy groups ofCNBR and epoxy groups of PP-g-GMA happened.The formed copolymers containing CNBR and PP-g-GMA components could locate at interfacial lay-ers between two blending components. Therefore,their interfacial behavior was greatly improved.

TEM images of sample C40 and U40 are shownin Figure 4. Here, ruthenium tetraoxide (RuO4)was used as a staining agent to replace osmium

tetraoxide (OsO4), since RuO4 was more sensitiveto stain the ether, alcohol, aromatic or amide moi-eties. As shown in Figure 4(b) (sample C40), therewas some macula at the interface of CNBR andPP-g-GMA phases. But this phenomenon was notobserved in uncompatibilized system (sampleU40). This was probably due to the fact that theaddition of PP-g-GMA introduced chemical reac-tions among carboxy groups of CNBR and epoxygroups of PP-g-GMA, and the in situ formed co-polymer located at the interfacial area of C40.RuO4 was a good staining agent for this copoly-mer. The macula appeared at the interface ofCNBR and PP-g-GMA was the black precipitateof ruthenium dioxide.25

Occurrence of the copolymer containing twoblending components at their interface would re-duce the interfacial tension, permit the reductionand homogeneous dispersion of size of CNBR par-ticles, and stabilize the matrix-domain morphol-ogy against gross segregation of CNBR particles.All the above effects would result in improvementof interfacial adhesion and mechanical propertiesof the blending system, as discussed in the corre-sponding sections.

Effect of CNBR Content on Morphologies ofCNBR/PP-g-GMA Blends

Morphology of CNBR/PP-g-GMA blends with dif-ferent CNBR content examined by AFM and TEMare shown in Figure 5 and Figure 6, respectively.As shown in these two figures, when the rubbercontent was less than 70% sphere, elliptical rub-

Figure 2. Morphology of caboxy nitrile rubber pow-der examined by using SEM.

Scheme 1. Reaction between CNBR and PP-g-GMA.

CNBR/PP-g-GMA AND CNBR/PP/PP-g-GMA THERMOPLASTIC ELASTOMERS 1045

ber aggregates could be observed. But irregularlyshaped rubber aggregates were observed whenthe rubber content was over 70% or 75%.

The ideal shape of CNBR domains in PP ma-trix should be spherical. However, it would be nottrue if CNBR was excessively saturated in PPmatrix. The critical content of dispersed phasecould be predicted theoretically.26,27 If all dis-persed particles were spheres, their size was iden-tical, and they arranged in hexagonal or cubicclose packing mode, the packing density k couldbe calculated by using the following relationship:

k � zV0/V, (1)

Where z was the number of particles per unit cell,V0 was the volume of the spherical particles asdefined by their constant radius and V was theunit cell volume. For CNBR/PP blending system,the calculated theoretical critical weight fractionof CNBR phase was 75.55% on the basis of theabove assumption, considering the density ofCNBR (0.98 g/cm3) and PP (0.905 g/cm3). Obvi-ously, this value was higher than the weight frac-tion (70%) of CNBR in the C30 sample. However,

Figure 3. Micrographs of sample U40 (a) and C40 (b) examined by AFM.

Figure 4. Micrographs of sample U40 (a) and C40 (b) examined by TEM.

1046 XU ET AL.

CNBR domains in C30 didn’t take the shape of asphere or ellipse. This was due to the fact thatCNBR particles didn’t own the same diameterand arrange in close packing morphology. Accord-ingly, this theoretical critical content was not anabsolute limit, and it was only a reference forpractical application.

Comparison of Thermal Behavior of CNBR/PP andCNBR/PP-g-GMA Blends

Crystallization temperatures (Tc), melting tem-peratures (Tm), crystallinity (Xc) and degree ofsuper-cooling expressed as (Tm � Tc) of PP orPP-g-GMA in CNBR/PP or CNBR/PP-g-GMAblends were shown in Table 1 and Table 2. Xc of

PP or PP-g-GMA in CNBR/PP or CNBR/PP-g-GMA blends was determined by using the follow-ing equation:

Xc ��Hf

fw�Hf0 � 100, (2)

Where �Hf was the specific enthalpy of fusion ofPP in a sample, fw was the weight fraction of PPor PP-g-GMA in a blend and �Hf

0 was the specificenthalpy of fusion of PP with 100% crystalline.Here, 8.7 kJ/mol of �Hf

0 was adopted for PP.28,29

As shown in Table 1 and 2, Tc of PP-g-GMAwas 13.5 °C higher and its Tm was 11.5 °C higherthan the related values of the neat PP. This fea-

Figure 5. AFM micrographs of CNBR/PP-g-GMA blends with different content ofCNBR. (a) C70 , (b) C40 , (c) C30 , (d) C25.

CNBR/PP-g-GMA AND CNBR/PP/PP-g-GMA THERMOPLASTIC ELASTOMERS 1047

ture could be tentatively attributed to the nucle-ating effect of GMA grafted onto PP molecularchains or GMA homo-polymer produced duringgrafting reaction between PP and GMA.

For CNBR/PP blends, Tc of PP didn’t changeevidently. But its Tm decreased about 2.5–3.5 °C,and Xc decreased about 2.0–8.5%. Decreasing ofTm and Xc of PP was introduced by kinetic effect,

Figure 6. TEM micrographs of the CNBR/PP-g-GMA blends with different content ofCNBR. (a) C60, (b) C50, (c) C40, (d) C30, (e) C25.

Table 1. Tc, Tm, Tm � Tc and Xc of CNBR/PP Blends

Sample U100 U70 U60 U50 U40 U30 U25

Tc (°C) 96.7 97.2 97.0 97.8 97.5 97.0 96.3Tm (°C) 143.2 140.7 140.2 140.0 140.2 139.7 139.7Xc (%) 31.1 29.1 29.1 27.4 27.8 26.8 22.5(Tm � Tc) (°C) 46.5 43.5 43.2 42.2 42.7 42.7 43.4

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since the presence of CNBR would hinder themotion and folding of PP molecular chains, whichaffected the formation of perfect crystals.

However, enhancement of both Tc and Tm ofPP-g-GMA in compatibilized CNBR/PP-g-GMAblends was observed, as shown in Table 2. Com-pared with the plain PP-g-GMA, Tc of PP-g-GMAin blends increased about 10 °C and Tm increasedslightly. These features suggested that both ther-modynamic and kinetic effects would influencethe crystallization behavior of PP-g-GMA inCNBR/PP-g-GMA blends. The kinetic effect camefrom the fact that the motion and folding of PPmolecular chains were hindered. And the thermo-dynamic effect mainly came from improvement ofthe miscibility between CNBR and PP-g-GMA,which was due to the reaction of carboxy groups ofCNBR and epoxy groups of PP-g-GMA. Theformed copolymers could act as a nucleatingagent during crystallization of PP-g-GMA,30–32

which could be verified by the POM micrographsand DSC data. As shown in Figure 7, the size ofspherulites of PP in sample C70 was much smallerthan that in sample C100. Reduction of the degreeof super-cooling (Tm � Tc) and enhancement of Xcof PP-g-GMA in CNBR/PP-g-GMA blends alsosupported the above explanation. As a result, itseemed to be that the thermodynamic effectplayed dominant action in this blending system,since enhancement of Tm, Tc and Xc and reductionof the degree of super-cooling (Tm � Tc) of PP-g-GMA in CNBR/PP-g-GMA were observed.

Effect of PP-g-GMA on the Rheological Behavior ofCNBR/PP/PP-g-GMA Blends

Apparent viscosities of U40, C4004, and C4020 sam-ples at 190 °C as a function of shear stress wereshown in Figure 8. These values decreased withincreasing shear stress. A pseudoplastic flow be-havior was observed, which arose from the ran-domly oriented and disentangled nature of molec-ular chains of two blending components.9

As shown in Figure 8, at a fixed shear stress,apparent viscosities of C4004 and C4020 werehigher than the value of U40, and the viscosity ofC4020 was higher than that of C4004. These fea-tures could be tentatively explained as follows.For a multi-component system, its apparent vis-cosity mainly depends upon its interfacial behav-ior. When strong interfacial adhesion presented

Table 2. Tc, Tm, Tm � Tc and Xc of CNBR/PP-g-GMA Blends

Sample C100 C70 C60 C40 C30 C25

Tc (°C) 110.2 120.8 121.3 119.9 120.5 120.8Tm (°C) 154.7 157.2 156.2 155.9 156.2 156.8Xc (%) 33.5 36.9 36.4 35.7 34.8 35.5(Tm � Tc)(°C) 44.5 36.4 34.9 36.0 35.7 36.0

Figure 7. POM micrographs of (a) C100 and (b) C70.

CNBR/PP-g-GMA AND CNBR/PP/PP-g-GMA THERMOPLASTIC ELASTOMERS 1049

among different phases, deformation of the dis-persed phase would be effectively transferred tothe continuous phase and the interlayer slipwould be avoided. So this blending system wouldown high apparent viscosity. As discussed in theprevious section, CNBR and PP were immisciblethermodynamically. After addition of PP-g-GMA,chemical reactions happened between carboxygroups of CNBR and epoxy groups of PP-g-GMA,which resulted in an in situ compatibilization be-tween CNBR and PP components. And the inter-facial adhesion was greatly improved. Therefore,the viscosity of the compatibilized blending systemwould be higher than the uncompatibilized one andincrease with increasing the content of PP-g-GMA.

Physical and Mechanical properties of CNBR/PP,CNBR/PP-g-GMA and CNBR/PP/PP-g-GMA Blends

The tensile strength, stress at 100% strain, elonga-tion at break, tension set, swollen volume (in gaso-line), and hardness of CNBR/PP and CNBR/PP-g-GMA blends with different blending ratios weregiven in Table 3. At a fixed weight ratio of CNBR toPP, tensile strength, stress at 100% strain, andelongation at break of CNBR/PP-g-GMA blendswere always higher than the related values of cor-responding uncompatibilized CNBR/PP blends. Forinstance, the tensile strength and elongation atbreak of the sample C25 were about two times of therelated values of the sample U25. The improvementof above parameters could be also attributed to thein situ compatibilization during reactive blending ofCNBR and PP-g-GMA, which improved the phasemorphology of the blending system, and enhancedthe interaction and adhesion at the interfacial areabetween CNBR and PP phases.

Effects of PP-g-GMA content on mechanicalproperties of CNBR/PP/PP-g-GMA blends wereshown in Table 4. The tensile strength, the stressat 100% strain, and the elongation at break of theblending system were greatly improved by addi-tion of 5% of PP-g-GMA. However, with increas-ing the content of PP-g-GMA further, no obviousenhancement of the above three parameters wasobserved. This feature suggested that a very lim-ited quantity of copolymers formed by the reac-tion of CNBR with PP-g-GMA was needed to sat-urate the interface of CNBR and PP phases. Afterthe interface was saturated by formed copoly-mers, there would be no possibility to further

Figure 8. Apparent viscosities of sample U40, C4004,and C4020 as a function of shear stress.

Table 3. Mechanical Properties of the CNBR/PP and CNBR/PP-g-GMA Blends with Different Content of CNBR

Tensile Strength(MPa)

Stress at 100%Strain (MPa)

UltimateElongation (%)

Tension Set(%)

SwollenVolumea (%)

Hardness(Shore D)

C70 28.9 27.1 239 99 21.5 59U70 23.5 21.0 179 73 26.3 51C60 27.2 23.9 228 70 23.5 56U60 19.6 18.2 150 71 27.5 49C50 26.2 20.7 211 66 24.4 51U50 16.3 15.6 117 38 28.8 44C40 23.5 18.0 190 57 24.9 47U40 13.3 13.0 102 28 30.2 40C30 20.1 13.9 176 36 27.0 40U30 12.0 — 78 15 30.9 32C25 18.0 12.5 171 32 27.2 39U25 9.3 — 73 11 31.3 29

aTest condition: 23 °C, 166 hours.

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improve the mechanical properties of the blend-ing system by increasing the content of PP-g-GMA.

As shown in Table 4, parameters such as ten-sion set and hardness of the blending system in-creased a little with increasing the content ofPP-g-GMA, which could be tentatively attributedto the fine morphology and homogeneous distri-bution of CNBR domains.

CONCLUSIONS

In this work, novel binary CNBR/PP-g-GMA andternary CNBR/PP/PP-g-GMA thermoplastic elas-tomers were prepared by using a reactive blend-ing route. Their morphology and structure, ther-mal behavior, rheological behavior, and mechan-ical properties were studied systematically. Theobtained main results could be summarized asfollows.

1. The compatibility between CNBR and PPwas greatly improved by addition of PP-g-GMA. Disappearing of peaks at 1700 cm�1

and 899 cm�1 attributed to stretching vibra-tion of epoxy groups and carboxy groups,and appearing of two new vibration peak at3498 cm�1 and 1123 cm�1 attributed to thestretching vibration ofOOH andOCOO(H)groups revealed the in-situ formation of acompatibilizer induced by the reaction be-tween carboxy groups of CNBR and epoxygroups of GMA in PP-g-GMA.

2. AFM and TEM Images of CNBR/PP-g-GMAblends revealed that after PP-g-GMA wasadopted to replace PP, a fine and homoge-neous distribution of CNBR domains wereobserved. The size of CNBR domains waslarger than 1�m, which was much higherthan the original dimension of fully cross-linked CNBR powders. Aggregation of

CNBR powders happened during blendingprocess. The formed compatibilizer by the insitu reaction of CNBR/PP-g-GMA located atthe interface of CNBR and PP-g-GMAphases.

3. Both thermodynamic and kinetic effectswould influence the crystallization behaviorof PP-g-GMA in CNBR/PP-g-GMA blends.The thermodynamic effect mainly camefrom improvement of the miscibility be-tween CNBR and PP-g-GMA. And the ki-netic effect came from the fact that the mo-tion and folding of PP molecular chains werehindered. It seemed that the thermody-namic effect played dominant action in thisblending system, since enhancement of Tm,Tc, and Xc and reduction of the degree ofsuper-cooling (Tm � Tc) of PP-g-GMA inCNBR/PP-g-GMA were observed.

4. At a fixed content of CNBR, the apparentviscosity of CNBR/PP/PP-g-GMA increasedwith increasing the content of PP-g-GMA.This feature could be tentatively explainedas that when strong interfacial adhesionpresented among different phases, deforma-tion of the dispersed phase would be effec-tively transferred to the continuous phase,the interlayer slip would be avoided, and theapparent viscosity of a blending systemshould increase.

5. The formed compatibilizer would locate atinterface between CNBR and PP-g-GMAblending components, which improved in-terfacial behavior and adhesion, preventedthe aggregation of rubber particles, and sta-bilized the morphology of blends. Therefore,the main mechanical properties such as thetensile strength, the stress at 100% strain,and elongation at break of CNBR/PP-g-GMA blends were greatly improved. ForCNBR/PP/PP-g-GMA ternary blends onlyseveral weight percent of PP-g-GMA was

Table 4. Mechanical Properties of CNBR/PP/PP-g-GMA Blends with Different Content of PP-g-GMA

Sample U40 C4005 C4010 C4015 C4020 C4025 C4030 C40

CNBR/PP/PP-g-GMA 60/40/0 60/35/5 60/30/10 60/25/15 60/20/20 60/15/25 60/10/30 60/0/40/Tensile Strength (MPa) 13.0 20.2 20.9 21.1 20.9 21.8 21.3 22.4Stress at 100% Strain (MPa) — 16.7 16.8 17.1 16.9 17.8 16.7 17.4Elongation at Break (%) 56 162 174 165 171 166 171 170Tension Set (%) — 37 42 38 38 41 37 40Hardness (Shore D) 41 41 42 44 41 44 44 46

CNBR/PP-g-GMA AND CNBR/PP/PP-g-GMA THERMOPLASTIC ELASTOMERS 1051

needed to saturate the interface of CNBRand PP phases and get good compatibilizingeffect.

The authors would like to acknowledge the financialsupport of the National Natural Science Foundation ofChina (Project No. 50390090) and the Special Funds forMajor State Basic Research Projects (G19990648).

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