PVC/环氧化天然橡胶共混型热塑性弹性体的制备

应用动态硫化技术．试验了共混温度、ＰＶＣ母料与环氧化天然橡胶（ＥＮＲ）母炼胶的混合时间、动态硫化时间、共混方式以及ＥＮＲ母炼胶门尼粘度等工艺因素对ＰＶＣ／ＥＮＲ共混型热塑性弹性体性能的影响。结果表明，当共混温度在１６０－１７０℃、混合时间为３ｍｉｎ、ＥＮＲ母炼胶门尼粘度ＭＬ（１＋４）１００℃＝１８时．采用一段共混方式可制得性能较好的热塑性硫化胶。通过Ｂｒａｂｅｎｄｅｒ塑性仪，对ＰＶＣ／ＥＮＲ共混物在密炼室中的动态硫化全过程进行了分析。     

天然橡胶/氯醚橡胶/相容剂共混物的研究

利用差示扫描量热法（ＤＳＣ）和相差显微镜（ＰＤＭ）对氯化聚乙烯（ＣＰＥ）、丁腈橡胶（ＮＢＲ２６）和环氧化天然橡胶（ＥＮＲ５０）作天然橡胶／氯醚橡胶（ＮＲ／ＥＨＲ）体系的相容剂进行了研究。通过考察共混胶的力学性能，确定了相容剂的适宜用量和共混时间。结果表明，ＣＰＥ，ＮＢＲ２６和ＥＮＲ５０能有效提高ＥＨＲ在ＮＲ中的分散程度，混炼时间１５ｍｉｎ，用量１０—１５份为宜。     

PVC／ENR／XNBR（NBR）动态硫化共混物

能干不氧化天然橡胶（ＥＮＲ）、聚氯乙烯（ＰＶＣ）和羧基丁腈橡胶（ＸＮＢＲ）之间的自硫化反应，实现了ＰＶＣ／ＥＮＲ／ＸＮＢＲ三元共混物的动态友化，由此得到了具有热塑性弹性体的一些典型特征的ＰＶＣ／ＥＮＲ／ＸＮＢＲ动态自硫化共混物。该人混物与自硫化反应不明显的ＰＶＣ／ＥＮＲ／ＮＢＲ共混物进行了比较，发现动态自硫化反应显著提高了共混物的综合性能。结果表明，当橡塑比为７０／３０时，前者的拉伸强度为１１．８     

亚乙基硫脲对PVC和PVC/ENR共混物的交联作用

从交联速率、压缩永久变形、凝胶质量分数、强伸性能和耐热性能等方面考察了亚乙基硫脲（ＥＴＵ）和ＥＴＵ／硫黄对ＰＶＣ及其与环氧化天然橡胶（ＥＮＲ）共混物的交联作用。结果表明,ＥＴＵ和ＥＴＵ／硫黄对ＰＶＣ及其与ＥＮＲ的共混物有明显的交联作用;交联后共混物的物理性能和耐热性能均有较大提高;适当增大ＥＮＲ用量,有利于提高共混物的热变形性能;ＰＶＣ／ＥＮＲ的共混比为７０／３０时,硫黄的最佳用量为１５份,促进剂选择促进剂ＤＭ／ＴＭＴＤ体系为佳。     

剑麻短纤维补强环氧化天然橡胶/PVC复合材料的性能研究

研究了剑麻短纤维用量和环氧化天然橡胶（ＥＮＲ）／ＰＶＣ共混比对剑麻短纤维补强ＥＮＲ／ＦＶＣ复合材料性能的影响。结果表明,该复合材料具有同的硬度和纵向拉伸强度、较低的扯断伸长率和扯断永外变形、良好的耐油和耐老化性能。剑麻短纤维的用量宜为３０份,ＥＮＲ／ＰＶＣ的共混比宜为７０／３０。     

PVC/环氧化天然橡胶共混型热塑性弹性体的性能与相态

在研究了ＰＶＣ与环氧化天然橡胶（ＥＮＲ）共混的工艺条件和配方优选的基础上，分别采用无填料、填充碳酸钙和填充炭黑的方法，制出了透明型、彩色型和黑色型３种ＰＶＣ／ＥＮＲ共混型热塑性弹性体。考察了其物理性能、耐热老化性能、耐油性能、挤出加工性能及多次返炼性能，还通过电子显微镜对相态结构进行了分析。     

氯化丁基橡胶/天然橡胶共混物性能的研究

研究了共混比及硫化体系对氯化丁基橡胶（ＣＩＩＲ）／天然橡胶（ＮＲ）共混物性能的影响，探讨了老化温度及防老剂对氧化锌／促进剂ＴＭＴＤ／促进剂ＤＭ硫化体系硫化的ＣＩＩＲ／ＮＲ共捐物耐热氧老化性能的影响。试验结果表明，氧化锌／促进剂ＴＭＴＤ／促进剂ＤＭ（５．０／１．５／１．０）硫化体系硫化的ＣＩＩＲ／ＮＲ共混物的拉伸强度和扯断伸长率与按共混比计算的平均值差别较小，尤其是拉伸强度与计算值完全一致。当共混物中ＣＩＩＲ用量超过５０份时，共混物的耐热氧老化性能明显改善。不同防老剂对ＣＩＩＲ／ＮＲ（５０／５０）共混物热氧老化的防护效能大小顺序为ＲＤ及４０１０＞４０１０ＮＡ＞ＭＢ＞Ｄ。防老剂ＲＤ先加入到ＮＲ中后再与ＣＩＩＲ共混．其防护效能更佳。     

ENR／CSM的自硫化研究

研究在没有任何硫化剂的情况下环氧化天然橡胶（ＥＮＲ－５０）和氯磺化聚乙烯（ＣＳＭ－４０）共混物的自硫化，以及共混比、填料品种及用量、间苯撑双马来酰亚胺与马来酸酐等活性剂、硫化温度和时间对交联程度和性能的影响。结果表明ＥＮＲ／ＣＳＭ共混体可以产生自硫化；共混比为５０／５０时交联密度最大，性能最佳，炭黑和白炭黑对该体系有好的补强作用，但白炭黑的补强作用比炭黑的好；间苯撑双马来酰亚胺及马来酸酐能活化自硫化体系；延长硫化时间及提高硫化温度均可增加交联作用，该自硫化体系没有返原现象。     

HPVC/SBR共混体系相容性的研究

采用动态硫化方法制备高聚合度聚氯乙烯（ＨＰＶＣ）／ＳＢＲ共混型热塑性弹性体,考察了单一组分相容剂「相容剂分别为ＮＢＲ２７０、ＮＢＲ Ｐ６５、ＣＰＥ和氢化苯乙烯－丁二烯、苯乙烯嵌段共聚物（ＳＥＢＳ）」、复合相容剂（ＳＥＢＳ／ＮＢＲ和ＣＰＥ／ＮＢＲ）及交联程度对ＨＰＶＣ／ＳＢＲ共混体系相容性的影响。结果表明,使用复合相容剂可明显改善ＨＰＶＣ／ＳＢＲ共混物的性能;动态硫化在改善共混物力学性能方面起主要作     

PVC／LLDPE／EVA／交联剂共混体系中增容－交联协同作用的研究

本文讨论了ＰＶＣ／ＬＬＤＰＥ共混体系中，ＥＶＡ、交联剂对共混物力学性能、相形态的影响。ＥＶＡ作增容剂，能与交联剂发生协同作用，改善ＰＶＣ、ＬＬＤＰＥ的两相分散性，增强两相粘接力，大幅度提高共混物的强度和韧性。     

Preparation and Electron Beam Irradiation of PVC/ENR/CNTs Nanocomposites

Poly (vinyl chloride), PVC/epoxidized natural rubber blend, ENR/carbon nanotubes, CNTs nanocomposites were prepared using melt intercalation and solution blending methods. In both preparation methods PVC: ENR: CNTs ratios were fixed at 50:50:2, while the 50/50 PVC/ENR blend without the addition of CNTs was used as control. The PVC/ENR/CNTs nanocomposites were exposed to electron beam (EB) irradiation at doses ranging from 0–200 kGy. The effects of two different preparation methods on the tensile properties, gel fraction and morphology of the PVC/ENR/CNTs nanocomposites were studied. Prior to EB irradiation, the addition of 2 phr of CNTs caused a drop in the tensile strength (Ts) of the 50/50 PVC/ENR blend, implying poor distribution of CNTs in the PVC/ENR blend matrix. However upon EB irradiation, the nanocomposites prepared by the melt blending method exhibited higher values of Ts as compared to the neat PVC/ENR blend due to occurrence of radiation-induced cross-linking in the PVC/ENR blend matrix. Transmission electron microscopy (TEM) images proved that a better dispersion of CNTs in PVC/ENR blend matrix can be achieved by melt intercalation compared to solution blending and the dispersion of CNTs was improved by irradiation. Scanning electron microscopy (SEM) results showed a distinct failure surface with formation of rough structure for the irradiated nanocomposites, which explains the higher values of tensile properties compared to the non-irradiated nanocomposites.     

Determination of optimum blending conditions for poly(vinyl chloride)/epoxidized natural rubber blends

An attempt to resolve the difficulties normally faced in preparing PVC-dominant PVC/ENR blends with the Brabender plasticorder is discussed. As expected, it was found that the mechanical properties of PVC/ENR blends are greatly influenced by the mixing parameters, which are further reinforced with evidence from both dynamic mechanical analysis (DMA) and morphological studies. Both techniques showed the attainment of compatible 50/50/PVC/ENR blends, the former a single glass transition temperature (T_g) and the latter a single-phase system, albeit their inherent properties are dependent on the blending parameters. By utilizing the correlation between mixing temperature and rotor speed derived, good PVC/ENR blends can be easily procured. © 1993 John Wiley & Sons, Inc.     

Mechanical Properties and Thermooxidative Aging of a Ternary Blend,Pvc/Enr/Nbr,Compared with the Binary Blends of Pvc

In the quest to improve the thermooxidative aging of the poly(vinyl chloride)/epoxidized natural rubber (PVC/ENR) blend, nitrile rubber (NBR) was incorporated into the blend to yield a ternary blend of PVC/ENR/NBR. A Brabender Plasticorder with a mixing attachment was used to perform the melt mixing at 150°C and 50 rpm followed by compression molding. The mechanical properties, dynamic mechanical properties, and thermooxidative aging behavior of the ternary blend were compared with those of the binary blends (i.e., PVC/ENR and PVC/NBR). It was found that the ternary blend exhibits mechanical properties which are superior to those of PVC/ENR. A single glass transition temperature (T _g) obtained from dynamic mechanical analysis coupled with synergism in the modulus and some other mechanical properties indicate that PVC, ENR, and NBR form a single phase (miscible system) in the ternary blend. Di-2-ethyl hexylphthalate (DOP) plasti-cizer improves the aging resistance of the blends generally, whereas the presence of CaCO₃ as a filler only imparts minor influences on the properties and aging resistance of the blends.     

Aspects of miscibility in poly(vinyl chloride)/epoxidized natural rubber blends. Part I: Mechanical and morphological properties

Miscibility in poly(vinyl chloride)/epoxidized natural rubber (PVC/ENR) blends was studied by examining evidence from tensile, impact, and physical properties. The observation of synergism in tensile strength, percent elongation at break, hardness, and relative density has reaffirmed PVC/ENR blends as miscible systems. Studies of impact properties, however, revealed that the blends are microheterogeneous in nature. This could be attributed to the large sizes of polymer molecules involved and the microgel content of ENR-50. Results from Fourier transform infrared spectroscopy (FTIR) revealed that hydrogen bonding is extensively involved in PVC/ENR systems. This evidence unveiled the exact nature of the specific interactions responsible for miscibility and hence the enhanced mechanical properties of PVC/ENR blends.     

Internal mixer studies of poly(vinyl chloride)/epoxidized natural rubber blends

Blends of polyvinyl chloride/epoxidized natural rubber (PVC/ENR) blends were studied. Their rheological properties were studied with a Brabrender Plasticorder. It was found that the rheological properties of any PVC/ENR blends are governed by their blending conditions. To ensure homogenous PVC/ENR blends, adequate and suitable blending conditions must be utilized. PVC thermoplastics phases enhances rigidity while ENR rubbery phases imparts flexibility and processability to the blends. With premixing, Ba/Cd/Zn-based PVC stabilizer is effective in stabilizing the PVC/ENR blends. Their properties are further enhanced by the addition of curatives.     

Effect of rubber content on mechanical properties and heat shrinkage of ethylene vinyl acetate copolymer blended with epoxidized natural rubber

Ethylene vinyl acetate (EVA, 18 mol % vinyl acetate) and epoxidized natural rubber (ENR, 50 mol % epoxidation) were blended in an internal mixer and compared to EVA. Dicumyl peroxide (DCP) was used as a curing agent. The blends consisted of 10–50 wt % of ENR and were compared with crosslinked EVA in terms of heat shrinkage, mechanical properties, and degree of crystallinity. It is found that the blends showed a decrease in mechanical properties with increasing ENR content because DCP was not a good vulcanizing agent of ENR. The addition of ENR did not affect heat shrinkability of EVA. The maximum heat shrinkage obtained was 80% for EVA and the blends. ENR did not affect thermal properties of EVA investigated by the differential scanning calorimetry. The X‐ray diffractometry showed discrepancy in degree of crystallinity before and after specimen stretching and after heat shrinking. It is believed that ENR particles decreased molecular orientation of EVA resulting in a decrease in degree of crystallinity but the remained orientation was sufficient for heat shrinking. The blend showed better extrudability than EVA after increasing take‐up speed. Therefore, the extruded tube prepared from the blend provided higher heat shrinkage than EVA tube. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

TENSILE PROPERTY OF EPOXIDIZED NATURAL RUBBER/NATURAL RUBBER BLENDS

The tensile strength and elongation at break of epoxidized natural rubber (ENR) blended with natural rubber (NR) was studied. ENR 25, ENR 50, and one grade of natural rubber (SMR L) were used as the elastomers. The composition of ENR was varied from 0% to 100% rubber. The accelerated sulfur vulcanization system was used throughout the investigation. The tensile property of unaged and aged samples was determined by using the Monsanto tensometer (T10) operating at 50 cm/min. Results show that the tensile strength and elongation at break passes through a maximum at 50% ENR for both ENR25/SMR L and ENR50/SMR L blends. This positive deviation from ideality is attributed to the mutual reinforcement of ENR and NR in the blends as a result of strain-induced crystallization. This synergistic effect is more pronounced in the case of ENR 25 due to the higher crystallinity and availability of more double bonds, which is more compatible to NR compared to ENR 50/NR blends. For the aged samples, a drop in the tensile property associated to the breakdown of the polysulfidic cross-link during aging is observed. A systematic study of the effect of sulfur concentration on the percentage retention of tensile property of the ENR blends after aging reveals that percentage retention decreases with increasing sulfur loading, which, in turn, enhances the formation of the polysulfidic cross-link; thus, more breakdown is observed in the rubber vulcanizate.     

Modification of PVC/ENR blends by electron beam irradiation

The effects of electron irradiation, with doses ranging from 20 to 100 kGy on the physical properties of poly(vinyl chloride)/epoxidised natural rubber blends (PVC/ENR50 blends) were investigated. The enhancement in tensile strength, elongation at break, hardness, and aging properties of the blends have confirmed the positive effect of irradiation on the blends. Crosslinking of the ENR50 phase proved to play a major role in the improvement of mechanical properties of blends. The results also revealed that at any blend composition the enhancement in properties depends on the irradiation dose which controls the degree of radiation-induced crosslinking. The single glass transition temperature obtained confirms that the blends remain miscible upon irradiation.     

Mechanical and thermo-oxidative properties of blends of poly(vinyl chloride) with epoxidized natural rubber and acrylonitrile butadiene rubber in the presence of an antioxidant and a base

Being polar and compatible with poly(vinyl chloride), epoxidized natural rubber (ENR) is similar in behaviour to acrylonitrile butadiene rubber (NBR). To assess the extent of this similarity, the mechanical properties of 50/50 blends of PVC with these two rubbers were compared. Their response to thermo-oxidative ageing in the presence of an antioxidant and a base was also investigated by ageing the blends at 100°C for 7 days. Studies involving mechanical properties and FTIR were used to evaluate the extent of thermal degradation. The results revealed that blends of ENR show mechanical properties which are as good as, and in some instances better than, those of the NBR blends. However, the ENR blends with PVC are very prone to oxidative ageing. This might be attributed to the susceptibility of the oxirane group to ring-opening reactions, particularly in the presence of PVC, which yields HCl as it degrades. The amine-type antioxidant 2,24-trimethyl-1,2-dihydroquinoline (TMQ) improved the oxidative stability of both blends. This was more significant in the ENR blend, which in some cases attained stability comparable with that of NBR. The addition of a base, calcium stearate [Ca(St)₂], did not show any influence in the PVC/ENR blend, even though it was expected to curb acid-catalysed degradation. Ca(St)₂, however, improved the oxidative stability of the PVC/NBR blend. The combination of optimum amounts of TMQ and Ca(St)₂ effectively improved the tensile strength of both unaged blends, without appreciable adverse effect on elongation at break. This combination also imparted stability better than that of TMQ alone.