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.     

Dynamically vulcanized acrylonitrile–butadiene–styrene terpolymer/nitrile butadiene rubber blends compatibilized by chlorinated polyethylene

Thermoplastic vulcanizates (TPVs) based on acrylonitrile–butadiene–styrene (ABS)/nitrile butadiene rubber (NBR) blends were prepared by dynamic vulcanization and then compatibilized by chlorinated polyethylene (CM). The effects of CM compatibilizer on the mechanical properties, Mullins effect, and morphological and dynamic mechanical properties of the TPVs were investigated systematically. Experimental results indicated that CM had an excellent compatibilization effect on the dynamically vulcanized ABS/NBR TPVs. Mullins effect results showed that the compatibilized ABS/NBR TPV had relatively lower internal friction loss than the ABS/NBR TPV, indicating the improvement of elasticity. Morphology studies showed that the fracture surfaces of ABS/CM/NBR TPVs were relatively smoother, indicating the improved elastic reversibility. DMA studies showed that the glass to rubber transition temperatures of ABS and NBR phases were slightly shifted toward each other with the incorporation of CM compatibilizer, which indicates the improvement of the compatibility. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40986.     

The effect of selective location of carbon nanotubes on electrical properties of thermoplastic vulcanizates

Three types of conductive thermoplastic vulcanizates (TPVs) were prepared by blending polypropylene (PP), carbon nanotubes (CNT), and carboxylic acrylonitrile butadiene ultrafine full‐vulcanized powdered rubber (xNBR‐UFPR). The CNT locations were different in these three types of TPVs, i.e., CNTs were localized in PP matrix, in the xNBR‐UFPR phase, or mainly in the interface. It had been found that TPV with CNTs localized mainly in the interface had the lowest conductive percolation threshold among these three types of TPVs. The volume resistivity of the TPV with 2 phr CNTs was as small as 220 Ω?cm. Moreover, the conductive TPV possessed good mechanical properties. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effects of Dynamic Vulcanization and Acrylic Acid on Properties of Recycled Poly(vinyl chloride)/Acrylonitrile Butadiene Rubber (PVCr/NBR) Blends

Effects of dynamic vulcanization and acrylic acid (AAc) on processability, mechanical properties, swelling behavior, morphology, and thermal stability of recycled poly(vinyl chloride)/acrylonitrile butadiene rubber (PVCr/NBR) blends were investigated. Blends were prepared in a Haake Rheomix at a temperature of 150°C and a rotor speed of 50 rpm. Recycled poly(vinyl chloride)/acrylonitrile butadiene rubber (PVCr/NBR) blends were also prepared as comparison. It was found that the dynamic vulcanization and the addition of acrylic acid improved the stabilization torque, mechanical energy, stress at peak, stress at 100% elongation (M₁₀₀), swelling resistance, and thermal stability but decreased the elongation at break of the blends. The introduction of a cross-link into the elastomer phase and better compatibility between PVCr and NBR are responsible for the enhancement of thermal stability and mechanical properties of dynamically vulcanized PVCr/NBR + AAc as evidence from the scanning electron microscopy (SEM) of the tensile fracture surfaces and infrared spectroscopy study of the dynamically vulcanized of PVCr/NBR + AAc shows.     

PP/EVAL/PP-g-MAH动态硫化体系的结构与性能研究

研究了聚丙烯/皂化乙烯-乙酸乙烯共聚物/马来酸酐接枝聚丙烯(PP/EVAL/PP-g-MAH)动态硫化体系的力学性能、相形态、结晶性能和动态机械性能。结果表明:PP-g-MAH能显著改善PP/EVAL动态硫化体系的力学性能和熔体流动速率(MFR)。当PP/EVAL/PP-g-MAH质量比为80/20/8时,材料的冲击强度较不加PP-g-MAH时提高了179.6%,达到74.1 kJ/m2,MFR为13.4 g/10min。PP-g-MAH能有效改善分散相的分散效果和两相相容性,并同时促进PP/EVAL动态硫化体系中PP的α晶和β晶的形成。PP-g-MAH的加入使PP/EVAL动态硫化体系中PP组分的Tg向低温方向移动。     

ATBN/MP复合增容NBR/PP热塑性硫化胶

研究了端氨基液体丁腈橡胶(ATBN)和马来酸酐接枝聚丙烯(MP)对NBR／PP共混体系的增容效果。采用TEM,SEM,DSC分析了NBR／PP共混体系的相态结构及其PP的结晶行为。结果表明,ATBN／MP是NBR／PP共混体系较理想的增容剂,当ATBN用量为5份,MP为10份时,增容效果最佳;增容剂存在一个临界胶束浓度(CMC),当增容剂浓度大于CMC时,增客剂的增容作用变差。增容良好的NBR／PP共混体系经过动态硫化后,可制备相态结构精细、性能优异的NBR／PP热塑性硫化胶;界面结合加强后,其流动性能略有下降。     

NBR／PP共混热塑性弹性体材料的研究

通过分别选择普通ＣＰＥ，高氯化ＣＰＥ，ＭＰ（马来酸酐接枝聚丙烯的简称），复合ＣＰＰ等对ＮＢＲ／ＰＰ共混体系进行增容研究；利用半有效硫化体系（Ｓ＋促进剂ＴＭＴＤ／促进剂ＣＺ）以及改性树脂硫化体系（改性树脂＋促进剂）为硫化体系对共混体系进行动态全硫化研究；用透射电镜研究其中部分共混体系的亚微观结构，讨论其与共混体系宏观性能间的关系；利用差热分析（ＤＳＣ）对连续相的结晶形态进行研究。实验研究表明，以ＣＰＰ为增容剂的共混体系经过动态全硫化后具有优良的耐热油及其他综合性能，适用于制造耐热油制品，具有广阔的应用前景。     

Thermal properties and morphology of isotactic polypropylene/acrylonitrile–butadiene rubber blends in the presence and absence of a nanoclay

A thermoplastic elastomer (TPE) nanocomposite based on polypropylene (PP), acrylonitrile–butadiene rubber (NBR), and a nanoclay (NC) was prepared in a laboratory mixer with a 54/40/6 weight ratio. The effects of NC on the thermal properties, crystalline structure, and phase morphology of the TPE nanocomposite were studied in this work. The results obtained from the nonisothermal crystallization of PP, PP/NBR, and PP/NBR/NC, which was carried out with differential scanning calorimetry, revealed that the overall rate of crystallization of PP decreased with the addition of NBR to PP and increased when NC was incorporated into the nanocomposite. In addition, the crystallite size distribution was more uniform for the PP phase crystallized in the nanocomposite versus the PP itself. Also, although the PP in the reference blend (PP/NBR) crystallized only in the α form, the crystalline structure of the PP incorporated into the nanocomposite was a mixture of α‐ and γ‐crystalline forms. The effects of NC on the phase morphology of PP/NBR blends prepared with three different cooling methods (quenching in liquid nitrogen, cooling between two metal plates at room temperature, and molding at a high temperature in a hot press) were studied. For the samples quenched in liquid nitrogen or cooled between metal plates, a particulate–cocontinuous morphology formed. However, for the samples prepared under a hot press, a laminar‐like morphology was observed. In all three cases, a similar particulate–cocontinuous morphology formed for the reference blend, but the rubber inclusions were always smaller than those of the TPE nanocomposite. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

NBR/PP TPV中PP的非等温结晶行为研究

通过不同方法制备了3种不同NBR/PP热塑性硫化胶(TPV),用差示扫描量热法研究TPV中PP的非等温结晶动力学,并分别利用Ozawa方程和莫志深方法对3种TPV中PP的非等温结晶行为进行解析。结果表明:TPV中NBR对PP的结晶起成核剂的作用,可提高PP的结晶速率,原位反应增容制备的TPV中PP的结晶速率最大;莫志深方法能很好地描述PP的非等温结晶过程。     

动态硫化丁腈橡胶/聚丙烯热塑性弹性体的耐油性能

研究了不同相容剂、硫化体系、增塑剂以及成型温度对动态硫化丁腈橡胶／聚丙烯热塑性弹性体(NBR／PPTPV)耐油性能的影响。结果表明,当端氨基液体丁腈橡胶(ATBN)为5份,马来酸酐接枝聚丙烯(MP)为10份时,ATBN／MP增容的TPV具有优异的耐油性能;酚醛树脂硫化TPV的耐油性能比过氧化二异丙苯(DCP)、溴化树脂硫化的TPV都要优越;聚酯增塑TPV的耐油性能优于邻苯二甲酸二辛酯(DOP)增塑的TPV;热成型温度对TPV的耐油性能影响不大。     

共混比对丁腈橡胶/氯醚橡胶性能的影响

研究了共混比时常规共混及动态硫化共混丁腈橡胶(NBR)／氯醚橡胶(ECO)的力学性能及加工流变性能的影响。结果表明,共混比对NBR／ECO胶料的力学性能及加工流变性能影响显著。NBR经动态硫化后,压缩永久变形及挤出胀大明显减小,拉伸强度提高,表现黏度随ECO用量的增大而减小。共混比对常规共混胶的表观黏度影响不大。动态硫化有利于改善NBR／ECO胶料的加工性能。     

Effect of spatial confinement on the development of β phase of polypropylene

The focus of this study was the effect of spatial confinement on the development of nucleating agent-induced β phase polypropylene (PP) in the dynamically vulcanized thermoplastic elastomers (TPVs) based on dynamically vulcanized PP/ethylene-propylene-diene rubber (EPDM) blend. The melting behaviors, crystalline structures and the morphologies of the blends were studied by differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD) and scanning electron microscopy (SEM). The results indicate that the EPDM phase undergoes a series of changes from the dispersed phase to a continuous one, and again to the dispersed phase with increased content of curing agent, and the PP component always shows itself in a continuous phase. In this process, with the content of the nucleating agent unchanged, the content of β phase PP in the blends initially increases a little and then decreases with increasing PF (Phenolic resin) content. We believe spatial confinement provides a good explanation for the development of β phase PP.     

Influence of oil contents in dynamically cured natural rubber and polypropylene blends

Mechanical, dynamic, thermal, and morphological properties of dynamically cured 60/40 NR/PP TPVs with various loading levels of paraffinic oil were investigated. It was found that stiffness, hardness, tensile strength, storage shear modulus, complex viscosity, glass transition temperature (T_g) of the vulcanized rubber phase, degree of crystallinity and crystalline melting temperature (T_m) of the polypropylene (PP) phase decreased with increasing loading levels of oil. This is attributed to distribution of oil into the PP and vulcanized rubber domains causing oil‐swollen amorphous phase and vulcanized rubber domains. An increasing trend of elastic response in terms of tension set and damping factor was observed in the TPVs with loading levels of oil in a range of 0–20 phr. It is supposed that a major proportion of oil was first preferably migrated into the PP phase and caused an abrupt decreasing trend of degree of crystallinity and T_m of the PP phase. The dispersed vulcanized rubber domains remained small as particles with a low degree of swelling. Increasing loading levels of oil higher than 20 phr caused a decreasing trend of elongation at break and elastomeric properties. Saturation of oil in the PP phase was expected and the excess oil was transferred to the rubber phase which thereafter caused larger swollen vulcanized rubber domains. The remaining amount of oil was able to separate as submicron pools distributed in the PP matrix. This caused lowering of T_g, T_m, crystallinity of PP phase as well as strength, elastomeric, and dynamic properties of the TPVs. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Microstructure‐properties correlations in dynamically vulcanized nanocomposite thermoplastic elastomers based on PP/EPDM

Thermoplastic vulcanized (TPV) nanocomposites were prepared in a laboratory mixer using EPDM, polypropylene of different viscosities, maleic anhydride modified polypropylene, an organo‐clay, and a sulfur‐based curing system. Based on the obtained results from X‐ray diffraction, transmission electron microscopy (TEM), scanning electron microscopy (SEM), differential scanning calorimeter, and mechanical properties, the microstructure of the prepared nanocomposites was found to be sensitive to the viscosity difference between the two phases and the clay content. X‐ray diffraction and TEM images of the TPV nanocomposites showed that clay was nearly exfoliated and randomly distributed into the polypropylene phase. The SEM photomicrographs of the dynamically vulcanized thermoplastic elastomer samples showed that the rubber particles were dispersed through the polypropylene in form of aggregates and their size increased with the introduction of clay. The nanoscale dimensions of the dispersed clay resulted in a significant improvement of the tensile modulus of the TPV nanocomposite samples, from 20 to 90% depending on clay content and the viscosity ratio of PP/EPDM. In the PP nanocomposites, the clay layers act as nucleating agents, resulting in higher crystallization temperature and reduced degree of crystallinity. Moreover, the oxygen permeability in the TPV nanocomposites was found to be lower than in unfilled but otherwise similar materials. POLYM. ENG. SCI., 47:207–217, 2007. © 2007 Society of Plastics Engineers.     

Effects of Composition and Dynamic Vulcanization on the Rheological Properties of PP/NBR Blends

Summary Rheological behavior of isotactic polypropylene (PP) and nitrile rubber (NBR) blends, in the composition range of 10–30-wt % NBR content were studied, with special reference to the effect of blend ratio, dynamic vulcanization and compatibilization. All blends were prepared in a twin-screw extruder. Capillary Rheometry was employed. Pseudoplastic behavior of blends was favored by increasing rubber content. The incorporation of NBR into PP lowered activation energies. Compatibilization of unvulcanized blends did not produce significant changes on flow behavior. Dynamically vulcanized blends provide unique processing characteristics that enable to perform well in both injection molding and extrusion. Received: 8 October 2002/Revised version: 3 March 2003/Accepted: 4 March 2003 Correspondence to M. Hernández     

动态硫化三元乙丙橡胶/聚丙烯热塑性弹性体的研究进展

介绍动态硫化三元乙丙橡胶(EPDM)/聚丙烯(PP)热塑性弹性体(TPV)的发展历程、配合体系、动态硫化工艺、应用领域和发展前景。相较于传统橡胶,动态硫化TPV作为新一代橡胶产品的典型代表,无论在生产工艺还是性能上均具有较大优势,且TPV对环境的影响较小,符合绿色环保理念。未来EPDM/PP TPV的研究方向将主要集中在环保、低挥发性有机物、高性能化和多功能化等方面。     

Enhancement of viscoelastic property of MABS processed by melt compounding and injection molding

This work is focused on developing a new type of polymer blend to improve the viscoelastic property of methyl methacrylate acrylonitrile butadiene styrene (MABS). A multi-phase binary polymer blend was prepared by melt mixing in a twin screw extruder with three different weight ratios (10, 20, and 30 wt%) with a dynamically vulcanized alloy consisting mostly of fully cured ethylene propylene diene rubber (EPDM) particles encapsulated in a polypropylene (PP) matrix trade name Santoprene and an engineered styrene based thermoplastic elastomer trade name VDT to enhance the viscoelastic property of the blends. The compatibility and performance of the binary blend were studied by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), Fourier transform infrared (FT-IR) spectroscopy, nuclear magnetic resonance (NMR), laser microscopy, scanning transmission electron microscopy (STEM) and tensile analysis. The DMA analysis of the samples revealed that the damping performance was significantly increased with the incorporation of the elastomeric phase into the MABS matrix. In addition, the morphological analysis revealed that VDT is more compatible with MABS compared to Santoprene. The NMR and FT-IR analysis further supported the reason for higher compatibility of VDT and MABS blend. The improvement of the damping properties has been observed with the increased wt % of the VDT and Santoprene in the blends.     

In situ reactive compatibilized polypropylene/nitrile butadiene rubber blends by zinc dimethacrylate: Preparation,structure, and properties

This study demonstrated an approach of compatibilization between polypropylene (PP) and nitrile butadiene rubber (NBR) by using zinc dimethacrylate (ZDMA) as a reactive compatibilizer in the presence of peroxides. The PP/NBR/ZDMA ternary blends with improved mechanical properties were successfully prepared via peroxide dynamic vulcanization. The resultant blends exhibited a significant increase in mixing torque and complex viscosity after incorporation of ZDMA. Morphology studies showed that the addition of ZDMA reduced the size of the crosslinked NBR phase. Transmission electron microscopy (TEM) combined with scanning electron microscopy (SEM) verified that the possible reactions between ZDMA, NBR, and PP increased the interfacial thickness and improved the compatibility between NBR and PP phase. Crystallization behavior analysis indicated that incorporation of ZDMA promoted the nucleation process of PP. Thermal gravimetric analysis (TGA) showed that the maximum degradation temperature was increased by ZDMA. POLYM. ENG. SCI., 54:2321–2331, 2014. © 2013 Society of Plastics Engineers     

有机蒙脱土/丁基橡胶/聚丙烯热塑性硫化胶的制备与性能

采用动态硫化法制备了有机蒙脱土(OMMT)/丁基橡胶(IIR)/聚丙烯(PP)热塑性硫化胶(TPV),考察了OMMT的用量和IIR/PP的质量比对TPV的物理机械性能、动态力学性能及热性能的影响.结果表明,当OMMT的用量为20份时,TPV的物理机械性能较佳,Payne效应最弱,OMMT均匀地分布在基体中,阻尼性能较好...     

Compatibilization of SBR/NBR blends using chemically modified styrene‐co‐butadiene rubber Part 2. Effect of compatibilizer loading

The present work focuses on the compatibization of styrene‐co‐butadiene rubber (SBR)/acrylonitrile‐co‐butadiene rubber (NBR) blends with dichlorocarbene modified styrene‐co‐butadiene rubber (DCSBR) as a function of concentration of compatibilizer and composition of the blend. FTIR studies, differential scanning calorimetry and dynamic mechanical analysis reveal molecular level miscibility in the blends in the presence of compatibilizer. The formation of interfacial bonding is assessed by analysis of swelling behaviour, cure characteristics, stress–strain data and mechanical properties. These studies show that the compatibilizing action of DCSBR becomes more prominent as the proportion of NBR in the blend increases. The resistance of the vulcanizate towards thermal and oil ageing improved with compatibilization. The change in technological properties is correlated with the crosslink density of the blends assessed from swelling and stress–strain data. © 2001 Society of Chemical Industry