剪切速率对乙烯-丙烯酸酯橡胶/聚偏氟乙烯热塑性硫化胶性能的影响

采用动态硫化法制备了乙烯-丙烯酸酯橡胶（AEM）/聚偏氟乙烯（PVDF）热塑性硫化胶（TPV）,考察了动态硫化过程中转子剪切速率对TPV微观相态结构及性能的影响。结果表明,动态硫化过程中转子的剪切速率越快,AEM和PVDF更易发生相转变,微观相态结构更加精细,形成具有“海-岛”结构的TPV。随转子的剪切速率加快,TPV的拉伸强度和扯断伸长率均先增大后减少。当剪切速率为75 r/min时,AEM/PVDF TPV具有较好的力学性能,拉伸强度达到14.84 MPa,扯断伸长率为246%,TPV具有更加优异的耐热油和热空气老化性能。     

过氧化物硫化体系对CM／XNBR共混物性能的影响研究

研究了不同用量过氧化物硫化体系对氯化聚乙烯橡胶（CM）／羧基丁腈橡胶（XNBR）共混硫化胶各相交联密度及热空气老化前后的物理机械性能、耐油性能等的影响规律。结果表明,随硫化体系用量的增加,共混硫化胶两相的交联密度都明显增加,交联密度差值变大;焦烧时间逐渐降低;硬度、拉伸强度、100％定伸应力、体积磨耗量呈上升趋势,永久变形、扯断伸长率明显降低,撕裂强度整体变化不大,常温下体积和质量变化率均很小,高温下体积和质量变化率明显降低后趋于平稳;热空气老化后,硬度、拉伸强度、100％定伸应力、撕裂强度整体上升,扯断伸长率整体下降,体积磨耗量整体变化不大;热油老化后,拉伸强度、100％定伸应力变化不大,扯断伸长率明显降低。     

Blends of polyacetal and ethylene-octene elastomer: Mechanical,dynamic mechanical and morphological properties

Polyacetal (POM) and ethylene octene copolymer(EOC) elastomers form immiscible blends with extremely low compatibility. In order to improve the dispersion, stability and properties of these blends, dynamic vulcanization was carried out in a twin screw extruder using dicumyl peroxide. The tensile strength decreased with increase in % elongation at break for both blend systems. There was a drastic decrease in impact strength for unvulcanized blends as the elastomer content increased and this was attributed to the coalescence of the elastomer particles as their content increased. In the case of dynamically vulcanized blends there was a significant increase in impact strength as the levels of elastomer increased. Dynamic mechanical analysis has been carried out to investigate the effect of blend composition and dynamic vulcanization on dynamic mechanical parameters such as storage modulus, loss modulus and loss factor. The results indicate gross incompatibility of POM and EOC blends. However, dynamically vulcanized blends show better adhesion between component polymers. The morphological studies reveal that the particle size and coalescence of elastomer was significantly reduced in comparison to unvulcanized bends. The phase adhesion was improved by dynamic vulcanization. Hence, it was observed that dynamic vulcanization effectively improves the morphology of the blend system and enhances the properties of polyacetal.     

环保型增塑剂对丙烯酸酯橡胶/乙烯丙烯酸酯橡胶共混胶性能的影响

研究了环保型增塑剂RS-107、RS-700、RS-735和TegMeR?812对丙烯酸酯橡胶(ACM)/乙烯丙烯酸酯橡胶(AEM)共混胶性能的影响,结果表明,随着增塑剂的加入,ACM/AEM共混胶的转矩明显下降,不同增塑剂对共混胶硫化影响的差别不大。加入4种增塑剂均使得共混硫化胶的硬度、拉伸强度和100%定伸应力减小而扯断伸长率增大,压缩永久变形性能和热稳定性都出现了不同程度的下降,耐低温性能得以改善,提高了耐IRM 903标准油性能,但对耐ASTM No 1标准油性能的影响不大。加入增塑剂使得共混胶的玻璃化转变温度明显向低温方向偏移、储能模量减小。其中,RS-700赋予共混硫化胶最好的综合性能。     

双马来酰亚胺在ACM橡胶中的应用

研究了N,N－间苯撑双马来酰亚胺（MPBM）对ACM橡胶力学性能、热空气老化性能以及耐热油性能的影响。结果表明：随着MPBM用量增大,ACM硫化胶的100％定伸应力和硬度增大,拉促强度有所提高,拉断伸长率下降,表观交联密度增大,热空气老化性能以及耐热油性能仍可保持较高水平。     

NBR／CSM并用比对共混胶耐热耐油性能的影响

研究了NBR／CSM并用比对共混胶硫化性能、力学性能、耐热老化性能和耐油性能的影响,并采用了扫描电镜分析方法表征共混胶浸油前后的结构。结果表明,随NBR用量的增加,共混胶的硫化效率提高,加工安全性能增强,耐油性能有所上升,但其耐热性能有所下降。当NBR／CSM并用比为60／40时,通过力学性能可知,共混胶中两相结构发生相反转。综合其性能,当NBR／CSM并用比为60／40时,共混胶具有最佳的耐热耐油性能,浸油后的抗拉强度保持率达到69％,断裂伸长率保持率达到86％,质量变化率为lO％,体积变化率为15％。     

PA6／POE-g-MAH体系的结构与性能研究

以动态硫化及非动态硫化方法制备了马来酸酐接枝乙烯-辛烯共聚物(POE-g-MAH)增韧的聚酰胺6(PA6) 共混物,研究了PA6／POE-g-MAH体系的力学性能以及POE-g-MAH在PA6中的分散状况。结果表明动态硫化 PA6／POE-g-MAH共混物的屈服强度、冲击强度、断裂伸长率及弯曲模量均高于非动态硫化方法制备的PA6／POE-g- MAH共混物,动态硫化的PA6／POE-g-MAH共混物可以在材料的刚性与韧性之间达到良好的平衡。扫描电子显微镜图像的统计分析表明,非动态硫化PA6／POE-g-MAH共混物中分散的橡胶相数均颗粒尺寸随组成中POE-g-MAH 的含量增大而不断增大,动态硫化的PA6／POE-g-MAH共混物中分散的橡胶相数均颗粒尺寸随POE-g-MAH含量的增大变化不大。     

SBR在全钢载重子午线轮胎下三角胶中的应用

研究丁苯橡胶(SBR)在全钢载重子午线轮胎下三角胶中的应用。结果表明:将全钢载重子午线轮胎下三角胶中的生胶由NR调整为NR与SBR并用(并用比为80/20),并调整硫化体系,胶料的门尼焦烧时间、硫化速度和硬度变化不大,定伸应力略有提高,拉伸强度及拉断伸长率略有降低,拉断永久变形减小,耐热老化性能和成品轮胎胎圈耐久性能相当,成本明显降低。     

Effect of dynamic vulcanization on the microstructure and performance of polyethylene terephthalate/elastomer blends

Blends of polyethylene terephthalate (PET) and ethylene‐ethyl acrylate‐maleic anhydride terpolymer (E‐EA‐MAH) were dynamically crosslinked in a one‐step extrusion process. An amine‐terminated glycol reacting with MAH moieties was used as the crosslinking agent. The effect of blend composition and dynamic crosslinking on the microstructure and mechanical properties were investigated. Blend ratios ranging from 80:20 to 20:80 PET/E‐EA‐MAH were studied. The region of phase inversion was located for uncrosslinked and dynamically crosslinked blends. The rheological characterization was also carried out for these blends in comparison with the neat materials. After dynamic crosslinking, the phase inversion is shifted from the 30–40% range to the 70–80% range of elastomer content. This shift is induced by the increase of viscosity and elasticity of the network formed. Dynamically crosslinked blends show significant improvements in impact strength but also exhibit a decrease in elongation at break.     

TPV及PP-g-MAH对回收PET的改性研究

以马来酸酐接枝聚丙烯(PP-g-MAH)为相容剂,回收聚对苯二甲酸乙二醇酯(rPET)为基体材料,动态硫化热塑性弹性体(TPV)为增韧材料,制备了rPET/TPV/PP-g-MAH共混物。用SEM、DMA及DSC分析了TPV及PP-g-MAH对rPET断面结构、储能模量和结晶性能的影响,并测试了共混物的力学性能。结果表明:加入9.95%TPV后,rPET/TPV共混物的熔融温度下降了2.33℃,结晶温度提高了2.82℃,断裂伸长率及缺口冲击强度明显提高,弯曲强度和拉伸强度略有下降;加入PP-g-MAH后,TPV球状粒子嵌入rPET基体材料中,共混物的相容性提高,储能模量明显增大,刚性增强,弯曲强度和拉伸强度有所提高;与纯rPET相比,含1.8%PP-g-MAH的rPET/TPV/PP-g-MAH共混物的断裂伸长率提高了129.06%,缺口冲击强度提高了47.02%。     

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。     

过氧化物交联聚烯烃弹性体的性能

采用过氧化物交联，讨论了交联剂、共交联剂、补强填充剂以及增地采用茂金属催化剂合成的乙烯－辛烯共聚物（ＰＯＥ）的物理机械性能的影响。和过氧化物交联后，ＰＯＥ的拉伸强度、扯断伸长率和扯断永久变形大幅度下降。加入共交联剂，可以提高交联程度，缩短硫化时间。加入炭黑，可以起到补强作用。提高１００％定伸应力、撕裂强度、伸强度和硬度，减小扯断伸长率和扯断永久变形。加入增塑剂降低了某些力学性能，但扯断伸长率增加，     

Vinyl acetate content and electron beam irradiation directed alteration of structure,morphology, and associated properties of EVA/EPDM blends

A series of ethylene vinyl acetate/ethylene–propylene diene elastomer (EVA/EPDM) blends with four types of EVAs with various vinyl acetate (VA) content, are prepared without and with crosslinker, trimethylol propane triacrylate (TMPTA). These are irradiated by electron beam (EB). As the VA content increases, the gel content, i.e., degree of crosslinking of EVA/EPDM blends, is increased. With increase in VA content, the modulus and tensile strength are decreased but elongation at break is increased due to increase in amorphousness. On EB irradiation, modulus and tensile strengths are increased but at the cost of elongation at break. Crystallinities of all blends are decreased with increase in VA and EB crosslinking. The thermal stability of EVA/EPDM blend is decreased with increase in VA content but increased after EB irradiation. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) show that with increase in VA content the miscibility of two polymers keeps on increasing, which even become more after EB irradiation. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43468.     

The Effect of Dicumyl Peroxide Vulcanization on the Properties & Morphology of Polypropylene/Ethylene-Propylene Diene Terpolymer/Natural Rubber Blends

ABSTRACT

This article discusses some properties such as tensile properties, chemical and oil resistance, gel content, crystallinity, and morphology of polypropylene (PP)/ethylene-propylene diene terpolymer (EPDM)/natural rubber (NR) blends. Dicumyl peroxide (DCP) was applied as a crosslinking agent. In terms of tensile properties, peroxide vulcanized blend shows higher tensile strength and tensile modulus (stress at 100% elongation, M₁₀₀) as compared with the unvulcanized blend. The elongation at break of the peroxide vulcanized blend is higher for the blend with NR rich content compared with the EPDM rich content. The improvements in chemical and oil resistance as well as gel content of peroxide vulcanized blends have also proved the formation of crosslinks in the rubber phase. Scanning electron microscopy (SEM) micrographs from the surface extraction of the blends support that the crosslinks have occurred during dynamic vulcanization. Dynamical vulcanization with DCP has decreased the percent crystallinity of blends that can be attributed to the formation of crosslinks in the rubber.     

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     

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。     

不同硫化助剂对EPDM/MVQ共混物性能的影响

研究了PDM和TAIC两种助硫化剂对共混胶性能的影响。实验结果表明,随着TAIC用量的增加,共混胶的硫化速度和硫化程度先增加后减小;随着PDM用量的增加,共混胶的硫化速度变化不大,说明PDM反应不是很剧烈,但交联程度是一直增加的。随着硫化助剂用量增加,TAIC共混胶的拉伸强度、拉断伸长率和撕裂强度均大于PDM共混胶,而压缩永久变形的变化率正好相反。老化后共混胶的硬度、拉伸强度和100%定伸应力均增加,但是拉断伸长率降低。说明在老化过程中胶料发生了二次硫化现象,交联程度进一步完善,交联网络的分布更加均匀,交联密度进一步增加。用平衡溶胀法测试共混物的交联密度,表明TAIC共混胶的交联程度大于PDM共混胶。     

Scrutinizing the influence of peroxide crosslinking of dynamically vulcanized EVA/TPU blends with special reference to cable sheathing applications

A novel thermoplastic vulcanizate (TPV) based on the blends of ethylene vinyl acetate/thermoplastic polyurethane (EVA/TPU) at various blend ratios has been developed via dynamic vulcanization at 180 °C using di‐(2‐tert‐butyl peroxy isopropyl) benzene (DTBPIB) peroxide as the cross‐linking agent. Modification of the EVA/TPU blends via dynamic crosslinking significantly improves the tensile strength and modulus of the system and the improvement is more significant for EVA/TPU 50/50 and 60/40 blends. AFM study shows that crosslinked EVA particles are dispersed in the continuous TPU matrix and the dispersed EVA domain sizes are relatively smaller in EVA/TPU 50/50 and 60/40 blends leading to good mechanical properties. FTIR spectroscopy has been used to characterize the specific chemical changes occurring due to dynamic vulcanization. This TPV has excellent retention of physico‐mechanical properties even after reprocessing twice and the blends also have very good thermal resistance as indicated by aging study. The samples were found to exhibit remarkable improvement in oil resistance property as compared to their uncrosslinked counterpart. The creep behavior of the blends significantly improves after dynamic crosslinking and blends with higher TPU content show better creep resistance. Volume resistivity of all the peroxide vulcanized blends is in the range of 10¹³ ohm cm, which is suitable for cable sheathing application. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43706.     

Poly(vinylidene fluoride)–acrylic rubber partially miscible blends: Phase behavior and its effects on the mechanical properties

A phase diagram of poly(vinylidene fluoride) (PVDF) and acrylic rubber (ACM) was plotted, and the effects of the extent of miscibility on the mechanical properties of the polymer blends were examined. A compressible, regular solution model was used to forecast the phase diagram of this blend. The model prediction, the lower critical solution temperature (LCST) over the upper critical solution temperature (UCST), was done qualitatively according to the experimentally determined phase diagram by differential scanning calorimetry (DSC), optical microscopy, and rheological analysis. These experimental methods showed that this system was miscible in ACM‐rich blends (>50% ACM) and partially miscible in PVDF‐rich blends. A wide‐angle X‐ray diffraction study revealed that PVDF/ACM blends such as neat PVDF had a characteristic α‐crystalline peak. The partially miscible blends displayed up to 350% elongation at break; this was a significant increment of this parameter compared to that of neat PVDF(20%). However, the miscible blends showed elongation of up to 1000% [again, a remarkable increase compared to chemically crosslinked ACM (220%)] and displayed excellent mechanical properties and tensile strength and a large elongation at break. For the miscible and partially miscible blends, two different mechanisms were responsible for this improvement in the mechanical properties. It was suggested that in the partially miscible blends, the rubbery depletion layer between the spherulite and the conventional rubber cavitations mechanism were responsible for the increase in the elongation at break, whereas for the miscible blends, the PVDF spherulite acted as a crosslinking junction. The stretched part of the tensile samples in the partially miscible blends showed characteristic β‐crystalline peaks in the Fourier transform infrared spectra, whereas that in the miscible blends showed α‐crystalline peaks. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1247‐1258, 2013     

DYNAMICALLY VULCANIZED THERMOPLASTIC ELASTOMER BLENDS OF NATURAL RUBBER AND POLYPROPYLENE

Dynamic vulcanization of a soft grade of thermoplastic natural rubber (TPNR) was carried out using several concentrations of Hexamethylene N, N′ bis (tert-butyl peroxy carbamate) (HBTP). The blends were melt mixed in a Brabender plasticorder. The effectiveness of dynamic vulcanization was investigated using the Brabender plastograms, swelling index measurements, rheological behavior by means of a capillary rheometer, dynamic mechanical properties, and tensile testing. It was found that varying the HBTP concentration had a great influence on the rheological behavior as well as the dynamic and tensile properties of the material. The increase of HBTP dosage resulted in an increase of the extent of crosslinking and caused an increase of the elastic modulus and a reduction of the loss modulus. The ultimate tensile strength and elongation at break also increased with increasing HBTP loading. The rheograms indicated that the blends exhibit a pseudoplastic behavior.