混炼型聚氨酯橡胶/聚十二内酰胺热塑性硫化胶动态硫化历程与性能

采用动态硫化方法制备了混炼型聚氨酯橡胶（MPU）/聚十二内酰胺（PA 12）热塑性硫化胶（TPV）,通过控制动态硫化时间探究了该TPV的动态硫化历程,同时研究了不同动态硫化阶段共混物的物理机械性能和动态力学性能。结果表明,随着动态硫化时间的延长,MPU/PA 12 TPV逐步完成相转变,在温度和剪切作用下,MPU相由连续相转变为分散相,而PA 12则由分散相转变为连续相;随着动态硫化时间的延长,MPU/PA 12共混物的储能模量升高,损耗模量降低,损耗因子减小。此外,随着动态硫化时间的延长,MPU/PA 12共混物的综合力学性能提高。     

Properties and preparation of olefin block copolymer/thermoplastic polyurethane blends

The properties of olefin block copolymer (OBC)/thermoplastic polyurethane (TPU) blends with or without maleic anhydride (MA) modification were characterized and compared. Compared with the OBC/TPU blends, OBC‐g‐MA/TPU blends displayed finer morphology and reduced domain size in the dispersed phase. The crystallization temperatures of TPU decreased significantly from 155.9 °C (OBC/TPU) to 117.5 °C (OBC‐g‐MA/TPU) at low TPU composition in the blends, indicating the inhibition of crystallization through the sufficient interaction of modified OBC with TPU composition. The modified systems showed higher thermal stability than the unmodified systems over the investigated temperature range due to the enhanced interaction through inter‐bonding. The highest improvement in tensile strength was more than fivefold for OBC‐g‐MA/TPU (50/50) in comparison with its unmodified blend via the enhanced interfacial interaction between OBC‐g‐MA and TPU. This also led to the highest Young's modulus of 77.8 ± 3.9 MPa, about twofold increase, among the investigated blend systems. A corresponding improvement on the ductility was also observed for modified blends. The modification did not vary the glass transition temperature and crystalline structure much, thus the improvement in the mechanical properties was mainly attributed to the improved compatibility and interaction from the compatibilization effect as well as increased viscosity from the crosslinking effect for modified blends. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43703.     

Exploring the Influence of Methylene Diphenyl Diisocyanate as a Modifier for Ethylene Vinyl Acetate/Thermoplastic Polyurethane Blends

Ethylene vinyl acetate (EVA)/thermoplastic polyurethane (TPU) blend at various blend ratios has been modified via reactive processing with 4,4′-methylene diphenyl diisocyanate (MDI). Modification of the blends with even small amount of MDI shows significant improvement in physico-mechanical properties for EVA/TPU 50/50 and 30/70 blends, and it is also supported by the superior melt rheological behavior and dramatic improvement in oil resistance property. After the treatment of electron beam (dose range: 50–150?kGy), radiation crosslinked EVA/TPU (30:70) blend reveals further improvement in various properties. This particular material can find potential application as cable sheathing component.     

交联剂用量对BR/EVA热塑性硫化胶性能的影响

采用动态硫化法制备了BR/EVA热塑性硫化胶(TPV),考查了硫化体系中硫黄用量对混炼胶的硫化行为、静态硫化胶的溶出物含量及性能的影响,并对BR/EVA型TPV的力学性能及微观结构进行了研究。结果表明,随着硫黄用量的提高,混炼胶硫化历程中的平坦期较长,但t90趋于明显降低,静态硫化胶溶出物含量及力学性能均呈下降趋势;当硫黄用量为0.5份时,静态硫化胶及BR/EVA TPV表现出良好的综合性能。显微镜照片表明,BR硫化胶的粒状物平均尺寸为5～10μm左右,较均匀地分散在EVA树脂基体中;FE-SEM的测试表明,TPV的断面平滑,TPV具有良好的形变回复性。     

Thermoplastic elastomeric blend of nitrile rubber and poly(styrene‐co‐acrylonitrile). I. Effect of mixing sequence and dynamic vulcanization on mechanical properties

The effects of dynamic vulcanization and blend ratios on mechanical properties and morphology of thermoplastic elastomeric (TPE) compositions, based on blends of nitrile rubber (NBR) and poly(styrene‐co‐acrylonitrile) (SAN), were studied. The TPE composition prepared by adding a rubber‐curatives masterbatch to softened SAN yields higher mechanical properties than that prepared by adding curatives to the softened plastic–rubber preblend. The blends having a higher rubber–plastic ratio (60 : 40 to 80 : 20) display thermoplastic elastomeric behavior, whereas those having a higher plastic–rubber ratio (50 : 50 to 90 : 10) display the behavior of impact‐resistant plastics. DSC studies revealed that NBR and SAN are thermodynamically immiscible. SEM studies of the thermoplastic elastomeric compositions show that SAN forms the matrix in which fine particles of NBR form the dispersed phase. It was further confirmed by dynamic mechanical thermal analysis. Dynamic vulcanization causes a decrease in the size of dispersed particles and improvement in mechanical properties. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1976–1987, 2003     

增容剂对硅橡胶/热塑性聚氨酯热塑性硫化胶性能的影响

采用动态硫化法制备了甲基乙烯基硅橡胶（MVQ）/热塑性聚氨酯（TPU）共混型热塑性硫化胶（TPV）,考察了增容剂的种类及用量对TPV力学性能及加工流变性能的影响。结果表明,随着增容剂用量的增加,TPV的力学性能呈先上升后下降的趋势。相比于乙烯丙烯酸共聚物和乙烯与乙酸乙烯嵌段共聚物,用聚烯烃弹性体接枝马来酸酐（POE-g-MAH）作为增容剂时TPV的力学性能更为优异。3种增容剂均能提高TPV中MVQ相与TPU相的相容性。当POE-g-MAH的用量为6份时,TPV中MVQ相与TPU相的玻璃化转变温度靠近程度最大,两相界面较为模糊,增容效果最佳。     

转子转速对乙烯-乙酸乙烯酯共聚物/三元共聚尼龙热塑性硫化胶性能的影响

使用密炼机,采用动态硫化工艺制备了乙烯-乙酸乙烯酯共聚物/三元共聚尼龙热塑性硫化胶（EVM/tPA TPV）和乙烯-乙酸乙烯酯-甲基丙烯酸缩水甘油酯共聚物/三元共聚尼龙热塑性硫化胶（EVM-GMA/tPA TPV）,研究了转子转速对两种热塑性弹性体体力学性能和耐热油等性能的影响。结果表明,在一定范围内提高转子转速,热塑性弹性体的力学性能呈上升趋势,当转子转速为80 r/min时,两种热塑性弹性体的综合力学性能最佳;当转子转速达到60 r/min以上时,两种热塑性弹性体的耐热油性能良好;随着转子转速的增加,两种热塑性弹性体的弹性得到改善;在相同转子转速条件下,EVM-GMA/tPA TPV比EVM/tPA TPV具有更好的力学性能、弹性和耐热油性能。     

充油BR/EVA/SBS/HIPS TPV的结构与性能

采用动态硫化法制备了充油顺丁橡胶(BR)/乙烯-醋酸乙烯共聚物(EVA)/苯乙烯-丁二烯-苯乙烯共聚物(SBS)/高抗冲聚苯乙烯(HIPS)共混型热塑性硫化胶(TPV),研究了在树脂相中填充芳烃油对TPV性能和亚微观结构的影响.结果表明,随着芳烃油用量的提高,TPV的硬度、拉伸永久变形、强度均呈显著下降趋势,而拉断伸长...     

Influence of Graphene Oxide on Thermally Induced Shape Memory Behavior of PLA/TPU Blends: Correlation with Morphology,Creep Behavior,Crystallinity, and Dynamic Mechanical Properties

In this study, shape memory is thermally induced in a series of graphene oxide (GO) filled poly(lactic acid)/thermoplastic polyurethane (PLA/TPU) blends, prepared via melt mixing process, and their shape recovery and shape fixity are measured, and the results are correlated with morphology, dynamic mechanical properties, crystallinity and creep recovery behavior. Morphological analysis by scanning and transmission electron microscopy reveals that the blends are immiscible, and GO platelets are mainly localized in the TPU phase of the blends, which lead to smaller and more elongated TPU droplets with improved interfacial adhesion being responsible for the improved shape recovery performance compared to the unfilled blend. A systematic enhancement found in storage and Young's modulus, tensile strength, creep resistance and creep recovery, and cold crystallinity as a result of GO inclusion are in agreement with the improved shape recovery, shape fixity and overall shape memory performance of the filled systems. The developed PLA/TPU/GO nanocomposites with highly improved mechanical properties can be utilized as a new class of environmentally friendly shape memory materials for a broad range of applications.     

New thermoplastic vulcanizate,composed of polypropylene and ethylene–vinyl acetate copolymer crosslinked by tetrapropoxysilane: evolution of the blend morphology with respect to the crosslinking reaction conversion

A thermoplastic vulcanizate (TPV) is tailored by a dynamic vulcanization process. TPVs can be processed as thermoplastics and have properties similar to conventional vulcanized rubbers. The main objective of our recent works was to tailor, by using the reactive extrusion process, a new TPV composed of polypropylene homopolymer (PP) as thermoplastic phase and ethylene–vinyl acetate copolymer (EVA) as elastomer phase, which is crosslinked by tetrapropoxysilane (TPOS) as crosslinking agent in the presence of dibutyl tin oxide (DBTO) as catalyst. Crosslinking is carried out through a transesterification reaction between the ester groups of EVA and the alkoxysilane groups of TPOS. This exchange reaction is catalyzed by DBTO at temperatures above 100 °C. The main advantage of this chemistry that it is non‐radical, and so prevent the degradation of PP, in comparison with crosslinking reactions using peroxides as initiators. Different reactive blends were prepared in the internal mixer of a Haake Plasticorder. In order to know how the crosslinking reaction has advanced, the EVA gel content and the volume swelling rate of the blend were measured. The aim of this study was to get a better understanding of the dispersion mechanism of EVA in the major phase during its dynamic vulcanization in the presence of PP in the minor phase. This paper deals with the correlation that exists between the evolution of the two‐phase blend morphology and the extent of the crosslinking reaction on the elastomer phase during the elaboration of a TPV. In particular, we showed that the correlation was almost the same for the elaboration of the TPV in the internal mixer of the Haake Plasticorder (discontinuous process) and in a twin‐screw extruder (continuous process). Copyright © 2004 Society of Chemical Industry     

Dynamic properties of rubber vibration isolators and antivibration performance of ethylene–propylene–diene monomer/nylon 6 blend systems

This article examines thermoplastic elastomers (TPEs) and thermoplastic vulcanizates (TPVs) as two types of elastomers from melt-blended and dynamically vulcanized ethylene–propylene–diene monomer (EPDM) rubber materials and nylon 6 plastic materials. A series of investigations were conducted on the mechanical properties, morphology, dynamic mechanical properties, hysteresis behavior, and dynamic antivibration properties with different nylon 6 contents. The experimental results showed that the incompatibility between EPDM and nylon 6 led to the easy destruction of the TPV materials in two interfacial polymers upon the application of an external force. Thus, after a dynamic vulcanization process, the mechanical properties of the EPDM/nylon 6 blends were not as good as those of the TPE materials. In terms of morphology, nylon 6 plastics were uniformly distributed in the EPDM/nylon 6 blends during the EPDM rubber phase before vulcanization was performed. After the dynamic vulcanization, phase inversion was produced in which rubber microparticles were formed and dispersed in the nylon 6 plastic phase. The results of dynamic mechanical analysis, compression vibration hysteresis behavior, and dynamic property antivibration experiments showed that the blends provided better vibration isolation and antivibration performance after the amount of nylon 6 was increased and EPDM and nylon 6 were blended through dynamic vulcanization. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008     

Dynamic mechanical behavior of high‐density polyethylene/ethylene vinyl acetate copolymer blends: The effects of the blend ratio,reactive compatibilization,and dynamic vulcanization

The effects of the blend ratio, reactive compatibilization, and dynamic vulcanization on the dynamic mechanical properties of high‐density polyethylene (HDPE)/ethylene vinyl acetate (EVA) blends have been analyzed at different temperatures. The storage modulus of the blend decreases with an increase in the EVA content. The loss factor curve shows two peaks, corresponding to the transitions of HDPE and EVA, indicating the incompatibility of the blend system. Attempts have been made to correlate the observed viscoelastic properties of the blends with the blend morphology. Various composite models have been used to predict the dynamic mechanical data. The experimental values are close to those of the Halpin–Tsai model above 50 wt % EVA and close to those of the Coran model up to 50 wt % EVA in the blend. For the Takayanagi model, the theoretical value is in good agreement with the experimental value for a 70/30 HDPE/EVA blend. The area under the loss modulus/temperature curve (LA) has been analyzed with the integration method from the experimental curve and has been compared with that obtained from group contribution analysis. The LA values calculated with group contribution analysis are lower than those calculated with the integration method. The addition of a maleic‐modified polyethylene compatibilizer increases the storage modulus, loss modulus, and loss factor values of the system, and this is due to the finer dispersion of the EVA domains in the HDPE matrix upon compatibilization. For 70/30 and 50/50 blends, the addition of a maleic‐modified polyethylene compatibilizer shifts the relaxation temperature of both HDPE and EVA to a lower temperature, and this indicates increased interdiffusion of the two phases at the interface upon compatibilization. However, for a 30/70 HDPE/EVA blend, the addition of a compatibilizer does not change the relaxation temperature, and this may be due to the cocontinuous morphology of the blends. The dynamic vulcanization of the EVA phase with dicumyl peroxide results in an increase in both the storage and loss moduli of the blends. A significant increase in the relaxation temperature of EVA and a broadening of the relaxation peaks occur during dynamic vulcanization, and this indicates the increased interaction between the two phases. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2083–2099, 2003     

Tailoring morphology to improve the gas‐barrier properties of thermoplastic polyurethane/ethylene‐vinyl alcohol blends

The morphology and helium‐barrier properties of thermoplastic polyurethane (TPU)/ethylene‐vinyl alcohol (EVOH) blends with and without dicumyl peroxide (DCP) were investigated by melting blending. A lamellar dispersion of EVOH with good helium‐barrier properties was observed in the TPU matrix with DCP. The evolution of the morphology of the blends is mainly related to the variation of the viscosity ratio between the dispersed phase and the matrix phase. Compared with pure TPU, lamellar morphology increased the helium‐barrier properties of the TPU/EVOH (60/40) blend by as much as 10‐fold. We also explored the effects of composition, DCP content, and blending sequence on the morphology and helium‐barrier properties of the TPU/EVOH blends. The morphology of the blends ranged from a droplet‐matrix to a lamellar structure. We determined the optimum amount of DCP to improve the helium barrier of the blends. The helium‐barrier properties of the blends prepared by direct blending were superior to those of the blends prepared by two‐segment blending, and the blends prepared by direct blending exhibited a well‐developed lamellar morphology. We compared the permeability of the samples with the theoretical results to explain the relationship between morphology and helium‐barrier properties. POLYM. ENG. SCI., 56:922–931, 2016. © 2016 Society of Plastics Engineers     

低硬度CM／EVA TPV的制备及性能

采用动态硫化法制备了氯化聚乙烯橡胶（CM）／乙烯一醋酸乙烯共聚物（EVA）热塑性硫化胶（TPV）,对其力学性能和动态粘弹行为进行了研究。结果表明：在实验范围内,动态硫化CM／EVATPV呈现出典型弹性体软而韧的应力一应变行为,当CM／EVA的共混质量比在80／20～60／40之间时,所制备的低硬度TPV表现出了良好的综合性能。橡胶加工分析仪（RPA）的研究表明,随着扫描频率的增加,CM／EVATPV的储能模量呈线性增长趋势,损耗因子则呈下降趋势;随着应变的增加,TPV表现出明显Payne效应,储能模量发生大幅度下降,损耗因子在应变大于10．O％后急剧增加。     

动态三螺杆挤出机制备热塑性硫化胶的研究

对比分析了动态热塑性硫化胶(TPV)的加工设备,着重介绍了附加振动力场的三螺杆反应挤出机的结构特点以及利用该机进行三元乙丙橡胶/聚丙烯(EPDM/PP)的动态全硫化,对制品的物理力学性能和微观结构分别进行了测试分析和电镜扫描。结果表明,振动力场作用下EPDM/PP共混体系反应挤出动态硫化加工可有效地实现动态硫化反应、硫化橡胶的粉碎和分散以及相态反转,振动力场的作用明显提高了TPV性能。     

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     

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     

Dynamic properties of NR/EVA polymer blends: Model calculations and blend morphology

The dynamic mechanical properties of blends of natural rubber (NR) and the ethylene–vinyl acetate copolymer (EVA), a thermoplastic elastomer, were investigated in terms of the storage modulus and loss tangent for different compositions, using dynamic mechanical thermal analysis (DMTA) covering a wide temperature range. Mean‐field theories developed by Kerner were applied to these binary blends of different compositions. Theoretical calculations were compared with the experimental small strain dynamic mechanical properties of the blends and their morphological characterizations. Predictions based on the discrete particle model (which considers one of the components as a matrix and the other dispersed as well‐defined spherical inclusions embedded in the matrix) agreed well with the experimental data in the case of 30/70 NR/EVA but not in the case of 70/30 NR/EVA blends. A 50/50 blend, where a cocontinuous morphology was revealed by SEM studies, was found to be approximately modeled by the polyaggregate model (where no matrix phase but a cocontinuous structure of the two is postulated). © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 165–174, 1999     

硫化体系对动态硫化EPDM/POE热塑性弹性体性能的影响

采用动态硫化的方法在Haake转矩流变仪上制备了三元乙丙橡胶/聚烯烃(EPDM/POE)热塑性弹性体(TPV),并分别对不同硫化体系和硫化剂用量对TPV交联密度和性能的影响进行了研究。结果表明,随硫化剂用量的增加,TPV的交联密度增大,其中硫黄硫化体系的TPV变化最明显;采用硫黄硫化体系和酚醛树脂硫化体系制备的TPV性能优于过氧化物硫化体系,并且DCP和硫黄分别在用量为0.5份,酚醛树脂在1.0份时性能较佳。     

Blends of thermoplastic polyurethane and polypropylene. I. Mechanical and phase behavior

Pure thermoplastic polyurethane (TPU), polypropylene (PP), and TPU/PP blends with different weight ratios prepared in a twin‐screw extruder were investigated by dynamic mechanical analysis (DMA), the universal tester for mechanical investigation, and by wide‐angle X‐ray diffraction (WAXD). The addition of PP above 20 wt % to the TPU stepwise changed the ductility and Young's modulus, i.e., apparently a kind of ductile → brittle transition occurred between TPU/PP 80/20 and TPU/PP 60/40 blends. This fact and the result of analysis of WAXD curves indicated matrix → dispersed phase inversion in this concentration region. TPU melt enabled easier migration of the PP chains and prolonged crystallization of PP matrix during solidification process affecting thus crystallite size, orientation, and crystallinity. In accordance to this fact, DMA results indicated partial miscibility of PP with polyurethane in the TPU/PP blends due to the lack of interfacial interaction and adhesion between the nonpolar crystalline PP and polar TPU phases. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104, 3980–3985, 2007