Effect of the compatibility on the morphology and properties of acrylonitrile–butadiene rubber/polypropylene thermoplastic vulcanizates

In this study, the morphologies of three types of acrylonitrile–butadiene rubber (NBR)/polypropylene (PP) thermoplastic vulcanizates (TPVs) (with an NBR/PP blend ratio of 70/30) were compared. The TPVs were (1) an ultrafine fully vulcanized acrylonitrile–butadiene rubber (UFNBR)/PP TPV made by the mechanical blending of UFNBR with PP, (2) a dynamically vulcanized NBR/PP TPV without the compatibilization of maleic anhydride grafted polypropylene (MP) and amine‐terminated butadiene–acrylonitrile copolymer (ATBN), and (3) a dynamically vulcanized NBR/PP TPVs with the compatibilization of MP and ATBN. The influence of the compatibility therein on the size of the dispersed vulcanized NBR particles and the crystallization behavior of the PP in the TPVs and the resultant properties are also discussed. As indicated by Fourier transform infrared spectroscopy, scanning electron microscopy, differential scanning calorimetry, polarizing microscopy, dynamic mechanical thermal analysis, and rheological and mechanical testing, the compatibility was significantly improved by the reactive compatibilization of MP and ATBN, which led to a uniform and fine morphology. The compatibilization increased the crystallization rate and reduced the size of the spherulites of PP. On the other hand, it was found that the dispersed vulcanized NBR particles lowered the degree of crystallinity. The better the compatibility of the blend was, the lower the degree of crystallinity and the storage modulus were, but the higher the loss factor and the processing viscosity were. All TPVs showed almost the same oil resistance, but the TPV prepared with reactive compatibilization had the best mechanical properties. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Investigation of crystallization behavior in dynamically vulcanized EPDM–nylon copolymer blends

A thermoplastic vulcanizate (TPV) of a ethylene–propylene–diene terpolymer (EPDM) and nylon copolymer (PA) was prepared by dynamic vulcanization. Maleic anhydride (MAH)–grafted EPDM (EPDM–g–MAH), MAH‐grafted EPR (EPR–g–MAH), and chlorinated polyethylene (CPE) were used as compatibilizers. The effect of dynamic vulcanization and compatibilizer on the crystallization behavior of PA was investigated. Differential scanning calorimeter measurement results showed no pronounced shift in the crystallization temperature for PA in EPDM–PA TPV compared to that for PA in the neat state, whereas the crystallization temperature increased after adding compatibilizer. The decrease in the crystallinity of TPVs was a result of the crystallization occurring in confined spaces between rubber particles. The equilibrium melting temperature (Tm⁰) of the PA copolymer was measured and was determined to be 157°C. The isothermal crystallization kinetics of PA in the neat and TPV states also was investigated. The crystallization rate was highest in the compatibilized TPV and lowest in the neat PA, whereas it was intermediate in the uncompatibilized TPV unvulcanized blends. Compared with unvulcanized EPDM–PA blends, the dynamic vulcanization process seemed to cause an obvious increase in the crystallization rate of the PA copolymer, especially when a suitable compatibilizer was used. This occurred because the dynamic vulcanization introduced fine crosslinked rubber particles that could act as heterogeneous nucleating centers. In addition, the use of a suitable compatibilizer permitted the formation of finely dispersed vulcanized rubber particles and therefore increased the density of the nucleating centers. The complex morphology of the blends was investigated by atomic force microscopy to evaluate the effect of compatibilizer on the size of the dispersed rubber particles. Compared with the morphology of TPVs with the same dosage of EPDM–g–MAH compatibilizer, the morphology of TPVs using EPR–g–MAH as compatibilizer showed much smaller dispersed rubber particles, which may have contributed to the higher crystallization rate. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 824–829, 2003     

Dramatic influence of compatibility on crystallization behavior and morphology of polypropylene in NBR/PP thermoplastic vulcanizates

In this study, the isothermal/nonisothermal crystallization behavior of polypropylene (PP) in acrylonitrile butadiene rubber (NBR)/PP thermoplastic vulcanizates (TPVs) prepared with three different processing methods, the compatibility effect therein, and the mechanism involved were studied. We concluded that the vulcanized NBR particles in TPVs act as heterogeneous nucleation centers and increase the number of nuclei. The crystallization rate of PP thereby increases and the growth of PP spherulites is restrained because of the isolation of vulcanized NBR particles. Since the addition of compatibilizer improves the compatibility of NBR and PP, the smaller and uniformly dispersed NBR particles are obtained, resulting in more and smaller PP crystals as well as higher crystallization rate, compared with Ultra-fine fully vulcanized NBR particles (UFNBR)/PP TPV and NBR/PP TPV without compatibilization. The isothermal crystallization kinetics of PP in TPVs obeys the Avrami equation, whereas the nonisothermal crystallization kinetics is well described by the equation of Mo et al.     

ZDMA补强EVA/CPE/NBR共混型热塑性硫化胶的Payne和Mullins效应研究

采用动态硫化法制备乙烯-醋酸乙烯酯共聚物(EVA)/氯化聚乙烯(CPE)/丁腈橡胶(NBR)共混型热塑性硫化胶(TPV),研究TPV的应力-应变行为、微观相结构、Payne和Mullins效应。结果表明:甲基丙烯酸锌(ZDMA)补强TPV的储能模量随应变的增大而显著下降,表现出典型的Payne效应;TPV存在明显的Mullins效应,相同拉伸比下,与EVA/CPE/NBR TPV相比,ZDMA补强TPV的最大应力、瞬时残余应变、内耗、损耗因子和软化因子均有所提高。     

Mechanical and sorption properties of poly(ethylene-co-vinyl acetate)(EVA) compatibilized acrylonitrile butadiene rubber/natural rubber blend systems

Poly (ethylene-co-vinyl acetate) (EVA) has been used as a compatibilizer for heterogeneous natural rubber/acrylonitrile butadiene rubber (NR/NBR) blends. NR/NBR (50/50) blends were compatibilized with varying amounts, from 0 to 10 parts per hundred rubber (phr), of EVA. The compatibility of the blend components in presence of EVA has been evaluated in terms of mechanical and sorption characteristics. The mechanical properties were found to be improved by the addition of EVA upto 6 phr. The solvent resistance of the compatibilized samples has been observed to be higher compared to the uncompatibilized blends; attributed to the increased interfacial adhesion between the blend components. DSC studies showed a shift of glass transition temperatures of the blend components towards higher temperatures indicating increased rigidity of the matrix in presence of EVA.     

撕裂模式下乙烯-丙烯酸共聚物/丁腈橡胶热塑性硫化胶的Mullins效应及其可逆回复

采用动态硫化法制备了乙烯-丙烯酸共聚物(EAA)/丁腈橡胶(NBR)热塑性硫化胶(TPV),对其撕裂强度、微观相结构、撕裂模式下的Mullins效应及热处理条件下的Mullins效应可逆回复行为进行了研究.结果表明,EAA/NBR TPV在EAA与NBR的质量比为40/60时的撕裂强度和应变较高.微观形貌观察可见,EA...     

Morphological evolution and properties of thermoplastic vulcanizate/organoclay nanocomposites

Nanocomposites composed of organoclay and thermoplastic vulcanizates (TPVs) based on uncompatibilized or compatibilized polypropylene (PP)/ethylene–propylene–diene rubber (EPDM) blends were prepared in this study. The morphology of the nanocomposites was studied with wide‐angle X‐ray diffraction and transmission electron microscopy, which suggested that the addition of the compatibilizer played a key role in determining the morphology of the composites because of their interaction with the clay surface. Scanning electron microscopy study indicated the changes in the morphology of the rubber particles. Dynamic mechanical analysis was also applied to the analysis of these phenomena. Moreover, for nanocomposites with uncompatibilized PP/EPDM blends as the matrix, the samples showed tensile enhancement compared with neat TPV. Although the addition of the compatibilizer changed tensile properties of the composites in a rather different trend, the tensile modulus increased dramatically when the compatibilizer was added. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40618.     

Carbon black reinforced thermoplastic vulcanisates based on ethylene–vinyl acetate copolymer/styrene–butadiene rubber blends

Thermoplastic vulcanisates (TPVs) based on ethylene–vinyl acetate copolymer (EVA)/styrene–butadiene rubber (SBR) blends were prepared by dynamic vulcanisation, with the TPVs being reinforced by carbon black (CB). Experimental results indicated that the mechanical properties of dynamically vulcanised EVA/SBR blends were enhanced remarkably by the incorporation of CB. Morphology study showed that the SBR particles with average diameter of 20?μm were dispersed evenly on the etched surface of EVA/SBR/CB TPVs. The Mullins effect could be observed in the stress–strain curves of EVA/SBR TPVs and EVA/SBR/CB TPVs during the uniaxial loading–unloading cycles. Compared with EVA/SBR TPVs, CB reinforced EVA/SBR TPVs had the relatively higher stress, residual deformation and internal friction loss.     

Dynamic‐mechanical analysis of MWNTs‐filled PC/ABS blends

In a systematic manner, the roles of MWNTs as filler and styrene acrylonitrile copolymer‐graft‐maleic anhydride (SAN‐MA) as compatibilizer, individually and together, on dynamic‐mechanical behavior of polycarbonate (PC)‐rich/acrylonitrile butadiene styrene terpolymer (ABS) blend were studied. The investigations were performed using small‐scale mixing in a one‐step procedure with a fixed MWNTs content of 0.75 wt% and a blend composition of PC/ABS = 70/30 w/w. PC/SAN blends and nanocomposites as simpler model system for PC/ABS were also studied to reveal the role of the rubbery polybutadiene (PB) fraction. It is found that the tendency of MWNTs to localize within the PC component in compatibilized PC/ABS was lower than in compatibilized PC/SAN blends. Dynamic mechanical analysis (DMA) revealed the dual role of SAN‐MA as blend compatibilizer and also promoter of MWNTs migration towards PC, where SAN‐MA to MWNTs weight ratio varied between 1 and 4. At the compatibilizer/MWNTs weight ratio of 1, MWNTs localized in PC component of the blends whereas increasing the compatibilizer/MWNTs ratio to 4 led to migration of MWNTs toward SAN or ABS component. In DMA studies, loss modulus normalization of the nanocomposites revealed the coexistence of mobilized and immobilized regions within the nanocomposite structure, as a result of MWNTs and compatibilizer loading. POLYM. ENG. SCI., 54:2696–2706, 2014. © 2014 Society of Plastics Engineers     

Effect of Silica on Uncompatibilized and Compatibilized Styrene Butadiene Rubber and Nitrile Rubber Blends

The present paper investigates the interaction of silica filler in uncompatibilized and compatibilized styrene butadiene rubber/nitrile rubber (SBR/NBR) blends of varying compositions. The use of a dynamic mechanical analyzer as a tool for confirming the compatibility by the addition of dichlorocarbene modified styrene butadiene rubber (DCSBR) in these blends has been described. The addition of silica in uncompatibilized as well as compatibilized blends has been found to be increasing the rheometric-processing characteristics such as maximum viscosity and rate of cure. The magnitude of these values has been found to be higher for compatibilized blends and for 50/50 composition. The optimum cure time has been found to be decreasing with silica loading regardless of the presence of the compatibilizer. The magnitude of optimum cure time has been found to be higher for uncompatibilized system and for the composition with higher SBR content. Enhancement in mechanical properties with the addition of silica has been observed for compatibilized blends, more intensely than uncompatibilized samples. A good correlation between mechanical properties and solvent sorption behavior has also been observed.     

PAAS含量对吸水膨胀型PVO／OMTPV性能的影响

采用交联聚丙烯酸钠（PAAS）为吸水材料,通过动态硫化法制备了聚氯乙烯（PVC）j氯化聚乙烯橡胶（cM）热塑性硫化胶（TPV）,并对其力学性能、微观相态结构及吸水行为进行了研究。结果表明：在实验范围内,PVC／PAAS／CMTPV呈现出典型弹性体软而韧的应力应变行为;PAAS在基体中实现了均匀分散,且随着PAAS含量的增加,PVC／PAAS／CMTPV的力学性能呈下降趋势;PVC／PAAS／CMTPV的吸水性能随着PAAs的含量增加而显著提高,且在PAAS加入量为60phr时急剧增加;由于基体的屏蔽作用,PVC／PAAS／CMTPV没有出现明显的溶出现象。     

ABS/NBR TPV压缩永久形变的可逆回复机制及模型构建

采用动态硫化法制备了丙烯腈-丁二烯-苯乙烯三元共聚物(ABS)/丁腈橡胶(NBR)动态硫化体系,研究了橡塑比和热处理温度对压缩永久形变的可逆回复的影响,探讨了可逆回复的机制并构建其数学模型。结果表明,提高橡塑比和热处理温度,均可显著加快热塑性硫化胶(TPV)压缩永久形变的可逆回复,且在接近基体玻璃化转变温度(Tg)时TPV压缩永久形变几乎完全可逆;基于TPV的微观结构和可逆回复曲线的特征,探讨压缩永久形变的可逆回复机制;采用广义Maxwell模型对压缩永久形变可逆回复过程进行了描述,并探讨了橡塑比和热处理温度对可逆回复各阶段松弛时间的影响。     

Mechanical properties and morphology of PP/ABS blends compatibilized with PP‐g‐2‐HEMA

Polypropylene (PP) and acrylonitrile–butadiene–styrene blends of different composition were prepared using a single‐screw extruder. The binary blend of PP/ABS was observed to be incompatible and shows poor mechanical properties. PP‐g‐2‐hydroxyethyl methacrylate (2‐HEMA) was used as a compatibilizer for the PP/ABS blends. The ternary compatibilized blends of PP/ABS/PP‐g‐2‐HEMA showed improvement in the mechanical properties. Electron micrographs of these blends showed a homogeneous and finer distribution of the dispersed phase. The mechanical performance increased particularly in the PP‐rich blend. The 2.5‐phr (part per hundred of resin) compatibilizer was observed to bring improvement to the properties. The suitability of various existing theoretical models for the predication of the tensile moduli of these blends was examined. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 72–78, 2003     

Study on the microstructure and properties of bromobutyl rubber (BIIR)/polyamide‐12 (PA12) thermoplastic vulcanizates (TPVs)

In this study, polyamide‐12 (PA12)/brominated isobutylene‐isoprene (BIIR) TPVs with good mechanical properties and low gas permeability were prepared by dynamic vulcanization in a twin‐screw extruder. The effects of three kinds of compatibilizers on the microstructure and properties of BIIR/PA12 TPV were studied. The compatibility between BIIR and PA12 was improved when maleated hydrocarbon polymeric compatibilizer is added. The reaction between maleic anhydride and amine in polyamide leads to the in situ formation of hydrocarbon polymer grafted polyamide which subsequently can be used to lower the interfacial tension between BIIR and polyamide. The compatibilizing effect of maleic anhydride modified polypropylene (PP‐g‐MAH) on BIIR/PA12 blends is the best among these compatibilizers because the surface energy of PP‐g‐MAH is very close to that of BIIR. The dispersed rubber phase of the blend compatibilized by PP‐g‐MAH shows the smallest size and more uniform size distribution, and the resulting TPVs show the best mechanical properties. The effects of fillers on the properties of BIIR/PA12 TPV were also investigated. The size of the BIIR phase increases with the increase in the content of CaCO₃. The modulus and tensile strength of TPVs increased with the increase in the content of CaCO₃ because of the reinforcing effect of CaCO₃ on TPVs. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43043.     

Dynamically vulcanized nitrile rubber/polypropylene thermoplastic elastomers

A new compatibilized method was used to prepare thermoplastic elastomer (TPE) of nitrile rubber (NBR) and polypropylene (PP) with excellent mechanical properties by dynamic vulcanization. Glycidyl methacrylate (GMA) grafted PP/amino‐compound was used as a compatibilizer. The effects of the curing systems, compatibilizer, PP type, and reprocessing on the mechanical properties of NBR/PP thermoplastic elastomers were investigated in detail. Experimental results showed that the addition of amino‐compound in the compatibilzer can significantly increase the mechanical properties of the NBR/PP thermoplastic elastomer. Compared with other amino‐compounds, diethylenetriamine (DETA) has the best effect. PP with higher molecular weight is more suitable for preparing NBR/PP thermoplastic elastomer with high tensile strength and high elongation at break. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2862–2866, 2002     

Improvement of the homogeneity of SBR/NBR blends using polyglycidylmethacrylate‐g‐butadiene rubber

Polyglycidylmethacrylate grafted butadiene rubber (PGMA‐g‐BR) was synthesized by a graft solution copolymerization technique. The PGMA content was determined through titration against HBr. The PGMA‐g‐BR was blended with styrene butadiene rubber/butadiene acrylonitrile rubber (SBR/NBR) blends with different blend ratios. The SBR/NBR (50/50) blend was selected to examine the compatibility of such blends. Compatibility was examined using scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and viscosity measurements. The scanning electron micrographs illustrate the change of morphology of the SBR/NBR rubber blend as a result of the incorporation of PGMA‐g‐BR onto that blend. The T_gs of SBR and NBR in the blend get closer upon incorporation of PGMA‐g‐BR 10 phr, which indicates improvement in blend homogeneity. The intrinsic viscosity (η) versus blend ratio graph shows a straight‐line relationship, indicating some degree of compatibility. Thermal stability of the compatibilized and uncompatibilized rubber blend vulcanizates was investigated by determination of the physicomechanical properties before and after accelerated thermal aging. Of all the vulcanizates with different blend ratios under investigation, the SBR/NBR (25/75) compatibilized blend possessed the best thermal stability. However, the SBR/NBR (75/25) compatibilized blend possessed the best swelling performance in brake fluid. The effect of various combinations of inorganic fillers on the physicomechanical properties of that blend, before and after accelerated thermal aging, was studied in the presence and absence of PGMA‐g‐BR. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1559–1567, 2006     

Influence of a crosslinked system on the morphology and properties of TPVs based on PA/NBR

The mechanical properties of thermoplastic vulcanizates (TPVs), depend strongly on their morphologies, which themselves depend on the properties of the primary polymers, the composition of the TPV, and the crosslink system and crosslink process. The morphology is defined during the dynamic vulcanization. This work deals with the study of the influence of crosslink systems on TPVs based on PA/NBR (copolyamide PA6/6‐6 and nitrile rubber) in a 40/60 composition. Dicumyl peroxide, bismaleimide, phenolic resin, a sulfur‐accelerated system, and dicumyl peroxide with two coagents were used as crosslinkers. TPVs were characterized by taking into account their mechanical strength, solvent resistance, compression set, and morphology. The curing system constituted by dicumyl peroxide and sulfur/bismaleimide as coagents resulted in a more defined morphology, and therefore the TPV exhibited the best properties. For these TPVs, a morphology consisting of spherical domains of rubber distributed homogeneously on the polyamide matrix could be observed. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

ABS/NBR热塑性弹性体的制备

采用动态硫化法制备了丙烯腈-T二-苯乙烯3元共聚物／丁腈橡胶（ABS／NBR）热塑性弹性体（TPV），研究了硫化剂种类及用量、NBR中丙烯腈含量、橡塑比、增塑剂等对TPV力学性能的影响。结果表明采用丙烯腈较高的NBR制备的TPV综合性能优良，在试验范围内硫黄用量1．5份为宜。适量的增塑剂可以降低TPV硬度，但会导致拉伸性能下降。实验表明，TPV重复加工性能较好。     

High density polyethylene/acrylonitrile butadiene rubber blends: Morphology,mechanical properties,and compatibilization

Polymer blends based on high-density polyethylene (HDPE) and acrylonitrile butadiene rubber (NBR) were prepared by a melt blending technique. The mixing parameters such as temperature, time, and speed of mixing were varied to obtain a wide range of properties. The mixing parameters were optimized by evaluating the mechanical properties of the blend over a wide range of mixing conditions. The morphology of the blend indicated a two-phase structure in which NBR phase was dispersed as domains up to 50% of its concentration in the continuous HDPE matrix. However, 70 : 30 NBR/HDPE showed a cocontinuous morphology. The tensile strength, elongation at break, and hardness of the system were measured as a function of blend compostion. As the polymer pair is incompatible, technological compatibilization was sought by the addition of maleic-modified polyethylene (MAPE) and phenolic-modified polyethylene (PhPE). The interfacial activity of MAPE and PhPE was studied as a function of compatibilizer concentration by following the morphology of the blend using scanning electron micrographs. Domain size of the dispersed phase showed a sharp decrease by the addition of small amounts of compatibilizers followed by a leveling off at higher concentrations. Also, more uniformity in the distribution of the dispersed phase was observed in compatibilized systems. The tensile strength of the compatibilized systems showed improvement. The mechanical property improvement, and finer and uniform morphology, of compatibilized systems were correlated with the improved interfacial condition of the compatibilized blends. The experimental results were compared with the current theories of Noolandi and Hong. © 1995 John Wiley & Sons, Inc.     

Effect of styrene–isoprene–styrene,styrene–butadiene–styrene,and styrene–butadiene–rubber on the mechanical,thermal, rheological,and morphological properties of polypropylene/polystyrene blends

The mechanical, thermal, rheological, and morphological properties of polypropylene (PP)/polystyrene (PS) blends compatibilized with styrene–isoprene–styrene (SIS), styrene–butadiene–styrene (SBS), and styrene–butadiene–rubber (SBR) were studied. The incompatible PP and PS phases were effectively dispersed by the addition of SIS, SBS, and SBR as compatibilizers. The PP/PS blends were mechanically evaluated in terms of the impact strength, ductility, and tensile yield stress to determine the influence of the compatibilizers on the performance properties of these materials. SIS‐ and SBS‐compatibilized blends showed significantly improved impact strength and ductility in comparison with SBR‐compatibilized blends over the entire range of compatibilizer concentrations. Differential scanning calorimetry indicated compatibility between the components upon the addition of SIS, SBS, and SBR by the appearance of shifts in the melt peak of PP toward the melting range of PS. The melt viscosity and storage modulus of the blends depended on the composition, type, and amount of compatibilizer. Scanning electron microscopy images confirmed the compatibility between the PP and PS components in the presence of SIS, SBS, and SBR by showing finer phase domains. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 266–277, 2003