Vulcanization kinetics of nano-silica filled styrene butadiene rubber

It was shown that the physical filler-polymer and filler–filler interactions, apart from the filler surface chemistry, has a substantial role in controlling the vulcanization kinetics of styrene butadiene rubber filled with nano-silica in a sulfur vulcanization system. Kinetic studies by the oscillating disc rheometer, differential scanning calorimeter, and swelling tests revealed that the vulcanization rate goes through a maximum as loading of silica increases, but conversion in crosslinking continuously decreases as the amount of silica increases. The effect of silica loadings on the vulcanization reactions was linked to the immobilization of rubber chains around particles as well as in a polymer-mediated filler network, which were differentiated by the nonlinear viscoelastic behavior of rubber vulcanizates. By surface modification of nano-silica, the accelerating/decelerating effects of nano-silica on the vulcanization reactions were altered corresponding to the non-linear viscoelastic behavior of the vulcanizates. Therefore, a mechanism was proposed which correlates vulcanization kinetics of rubber to the dynamics of chains influenced by the reinforcing fillers.     

Effect of iron oxide on vulcanization kinetics and electrical conductance of butyl rubber composites

This paper investigates the effect of iron oxide concentration on the vulcanization process, electrical conductance during swelling in kerosene, and sheds some light on the possible mechanism of vulcanization kinetics. The rate and degree of crosslinking have been evaluated as a function of Fe₂O₃ concentration. It was found that the characteristic time constant during vulcanization decreases as the Fe₂O₃ concentration increases. The activation energy of the crosslinking reaction is calculated. An abrupt decrease in electrical conductance appears after a characteristic time of swelling. A modified model is suggested to calculate the separation distance in the conductive rubber matrix. The effect of microwave irradiation on electrical conductance and separation distance between conductive aggregate of butyl rubber (IIR) composites is also studied. Fe₂O₃ inhibits the degradation of IIR composites and microwave irradiation enhances the texturing microstructure of rubber matrix. © 2000 Society of Chemical Industry     

Study on peroxide vulcanization thermodynamics of ethylene–vinyl acetate copolymer rubber using 2,2,6,6,‐tetramethylpiperidinyloxyl nitroxide

A step forward in the understanding of rubber vulcanization with organic peroxides is provided by combining a proper arrangement between polymer, vulcanizing agent and cure conditions. For this purpose, an ethylene–vinyl acetate copolymer with a high content of vinyl acetate (70 mol%) was used since a fully saturated polymer backbone allows its vulcanization via peroxide. For the range of conditions analysed here, it is shown that the predominant process taking place is crosslinking via radical recombination, minimizing or even avoiding undesirable secondary reactions such us polymer degradation. Once conditions had been optimized, peroxide vulcanization was analysed in more depth in the presence of 2,2,6,6‐tetramethylpiperidinyloxyl, which is a mediating stable free radical commonly used in controlled radical polymerization. Consequently, it was possible to differentiate the termination reaction from the initiation and propagation steps, allowing the determination of the enthalpy of formed C–C crosslinks as measured using calorimetry. It was possible to isolate and determine the contribution of the crosslinking pathway from the global vulcanization reaction by means of calorimetric methods at optimum conditions. In fact, this simple methodology could be an important tool for understanding in detail the complex peroxide vulcanization of elastomers since reactions involved in this process determine the final network structure, and thus the final elastic properties of these compounds.     

水基硅橡胶

简要回顾了室温硫化硅橡胶及水基硅橡胶的发展过程，介绍了水基硅橡胶的制备方法及交联机理，并对其交联过程、性能及用途作了较详细的阐述。     

Vulcanization of butyl rubber by p-quinone dioxime

The vulcanization of butyl rubber by p-quinone dioxime oxidized by red lead and tetrachloroquinone was investigated. The maximum physical effective crosslinking density of the vulcanizates appeared to be when p-quinone dioxime and the oxidizing agent were equimolar. The formation of one physical effective crosslink required one molecule of p-quinone dioxime. Chemical reactions are suggested for the vulcanization steps.     

促进剂M-La的合成及对天然橡胶的硫化促进作用

采用沉淀法用对氨基苯甲酸、氢氧化钠和硝酸镧在乙醇环境下合成了促进剂对氨基苯甲酸镧(M-La),研究了其对天然橡胶硫化的促进作用。通过红外光谱分析、热分析和元素分析等确定所合成促进剂M-La的分子式为La(C_7 H_6 NO_2)_3·2 H_2O。硫化性能测试结果表明,随着促进剂M-La用量的增加,天然橡胶的硫化速率指数由139增加至227,焦烧时间逐渐延长而正硫化时间基本维持不变,硫化胶的加工安全性不断增强;硫化胶交联密度由最初的1.95×10~(-4) mol/g逐渐增大至2.41×10~(-4) mol/g。促进剂M-La对天然橡胶硫化的促进作用比较明显。     

Effect of temperature on the course of thiuram-accelerated sulfur vulcanization

Tetramethylthiuram disulfide-accelerated sulfur vulcanization of styrene-butadiene rubber has been investigated at temperatures from 100°C to 170°C over 0.5 to 600 min. Continuous measurements in a Vuremo curemeter were used to estimate the extent of crosslinking, which was plotted against cure time. Apart from the induction period (t_i), the kinetic graphs are satisfactory represented by a rate equation assuming three independent first-order reactions: fast crosslinking, degradation, and slow crosslinking. The rate equation contains seven kinetic parameters. Over the temperature range studied, there is no difference between the values of activation energy for t_i^?1, for fast crosslinking, and for degradation. The activation energy of slow crosslinking only is significantly greater. Due to the presence of Aerosil, the reciprocal values of the induction periods and the values of the ultimate extents of fast crosslinking are increased, and the values of the rate constants of degradation and slow crosslinking are decreased. Simultaneously, the activation energy of slow crosslinking is also significantly decreased. On the basis of these results, the proposed theory of tetramethylthiuram disulfideaccelerated sulfur vulcanization supposing that zinc dimethyldithiocarbamate is the actual accelerator in this type of curing system is discussed.     

硅橡胶泡沫材料硫化特性分析

采用橡胶硫化仪研究了溶析成孔工艺制备的硅橡胶泡沫材料的硫化特性 ,分析讨论了硅橡胶的结构、成孔剂用量对硫化特性的影响规律。研究表明 ,苯基对硅橡胶的硫化有延迟作用 ,胶料中成孔剂对硫化有一定影响 ,成孔剂的刚性和占位作用削弱了胶料的交联 ,不影响硫化的成孔剂适宜用量为 2 0 0～ 2 3 0份     

挤出用溴化丁基橡胶硫化体系的研究

溴化丁基橡胶几种典型硫化体系的对比实验,结果表明,用氧化锌体系硫化的溴化丁基橡胶具有良好的焦烧安全性,比较适宜于挤出用;加入促进剂HVA-2,可显著提高胶料的硫化速度和交联程度,并改善焦烧安全性;当氧化锌用量为4份,HVA-2用量为1.5份时,胶料具有较佳的综合物理性能和加工安全性。     

Effects of modified silica on the co-vulcanization kinetics and mechanical performances of natural rubber/styrene–butadiene rubber blends

Rubber blends are widely used for combining the advantages of each rubber component. However, to date, how to determine and distinguish the vulcanization kinetics for each single rubber phase in rubber blends during the co-vulcanization process is still a challenge. Herein, high-resolution pyrolysis gas chromatography–mass spectrometry (HR PyGC-MS) was employed for the first time to investigate the vulcanization kinetics of natural rubber (NR) and styrene–butadiene rubber (SBR) in NR/SBR blends filled with modified silica (SiO₂). The reaction rates of crosslinking of each rubber phase in NR/SBR were calculated, which showed that the crosslinking rates of NR were much lower than those of SBR phase in the unfilled blends and blends filled with unmodified and silane modified silica. Interestingly, the vulcanization rates of NR and SBR phase were approximately same in the vulcanization accelerator modified silica filled blends, showing better co-vulcanization. In addition, the vulcanization accelerator modified silica was uniformly dispersed and endowed rubber blends with higher mechanical strength compared to the untreated silica. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48838.     

白炭黑补强异戊橡胶和天然橡胶性能的对比研究

采用白炭黑填充补强异戊橡胶(IR)和天然橡胶(NR),分别研究其硫化特性、机械力学性能、热空气老化性能和动态力学性能.结果表明:白炭黑补强的IR比NR硫化速度快,焦烧时间短,交联密度与NR接近;NR的机械力学性能优于IR;随着白炭黑用量增加,IR的耐老化能力逐渐增强,NR在白炭黑用量为20份时耐老化性能最好;在0℃时,IR的损耗因子大于NR的损耗因子,在60℃时,IR的损耗因子小于NR的损耗因子.     

助交联剂在氢化丁腈橡胶中的应用研究

研究了添加不同用量的助交联剂齐聚酯和三甲基丙烯酸三羟甲基丙烷酯(TMPTMA)氢化丁腈橡胶的硫化特性、力学性能,并对比了两种助交联剂对氢化丁腈橡胶的硫化特性、力学性能、老化性能、高温拉伸性能、耐磨性能和加工性能的影响。结果表明：随着齐聚酯和TMPTMA含量的增加,橡胶的扭矩增大,硫化时间缩短;拉伸强度基本不变,硬度、100%定伸应力、撕裂强度逐渐提高,拉断伸长率、回弹性减小。与添加齐聚酯的橡胶相比,添加TMPTMA橡胶的扭矩较大,硫化时间较短;对比添加齐聚酯和TMPTMA的橡胶,它们的力学性能、老化性能、高温拉伸性能和耐磨性能都非常接近,可见它们在硫化过程中的作用原理相似。由橡胶加工分析仪可知,添加TMPTMA橡胶的储能模量较小,损耗因子较大。     

配方体系对HNBR/HXNBR并用胶门尼黏度和硫化特性的影响

采用门尼黏度仪和无转子硫化仪研究了氢化羧基丁腈橡胶(HXNBR)的添加量、硫化/活化体系和补强体系对氢化丁腈橡胶(HNBR)/HXNBR并用胶门尼黏度和硫化特性的影响。结果表明,随着HXNBR用量的增加,HNBR/HXNBR并用胶的门尼黏度呈线性增加趋势;过氧化二异丙苯(DCP)/三羟甲基丙烷三甲基丙烯酸酯(TRIM)交联体系的硫化时间和交联程度高于DCP/三烯丙基异氰脲酸酯(TAIC)组合,添加活化剂MgO会提高其交联程度;另外,HNBR/HXNBR并用胶体系的门尼黏度随着炭黑的结构度和填充量的增加而增大。     

Effect of thiourea on thiuram-accelerated sulfur vulcanization and its significance for vulcanization mechanism

Tetramethylthiuram disulfide-accelerated sulfur vulcanization of natural rubber has been investigated at temperatures from 100°C to 140°C. Continuous measurements in a Vuremo curemeter were used to estimate the extent of crosslinking, which was plotted against cure time. The linearized forms of the cure curves clearly show that at lower cure temperatures, the course of vulcanization differs significantly from the first-order rate law. These digressions were removed by the addition of thiourea, which simultaneously speeds up the course of vulcanization and diminishes its activation energy on the one hand but, on the other hand, diminishes the ultimate extent of crosslinking. On the basis of the above results, the mechanism of thiuram-accelerated sulfur vulcanization, in which ionic and radical reactions take place, is discussed.     

Short fibers as reinforcement of rubber compounds

The effect of aramid, glass and cellulose short fibers on the processing behavior, crosslinking density and mechanical properties of natural rubber (NR), ethylene‐propylene‐diene terpolymer rubber (EPDM) and styrene‐butadiene rubber (SBR) has been investigated. Two fiber percentages (10 and 20 phr) were added to the rubber. The results have shown that the above‐mentioned fibers, especially aramid fibers, are effective reinforcing agents for these rubbers, giving rise to a significant increase in mechanical properties, such as tensile modulus and strength, and tear and abrasion resistance. Moreover, a significant decrease in the time to reach 97% of curing, t′_c (97) is observed, which indicates that the fibers tend to increase the vulcanization rate, regardless of the rubber used. Fibers give also rise to an increase in crosslinking, especially the aramid fibers.     

原位改性纳米氧化镁/顺丁橡胶复合材料的制备与性能

采用原位改性的方法制备了硅烷偶联剂Si 75 改性纳米氧化镁/顺丁橡胶复合材料,通过橡胶加工分析仪、扫描电镜等研究了其硫化特性、物理机械性能及动态力学性能。结果表明,当改性剂的用量为填料质量的3%时能有效提高纳米氧化镁/顺丁橡胶胶料的硫化速率和交联程度,且硫化胶的综合物理机械性能最好; 与未改性氧化镁填充的顺丁橡胶相比,改性氧化镁与橡胶之间的相互作用得到了增强,纳米氧化镁在橡胶中的分散性有了较大程度的改善,从而提高了改性纳米氧化镁/顺丁橡胶硫化胶的物理机械性能和损耗因子。     

Thermovulcanization of polychloroprene rubber and its blends with poly(vinyl chloride)

Heat and mechanical stressing at higher temperatures effect changes in polychloroprene rubber leading to network formation. During thermovulcanization of polychloroprene rubber in the temperature range of 150–200°C, two reactions have been observed and their kinetic parameters determined. When the rubber is stressed by shearing forces, the rate of degradation crosslinking is fairly high even at relatively low temperatures (90–150°C). Thermovulcanization of polychloroprene rubber/poly(vinyl chloride) blends has been investigated in the entire concentration range at 180°C. Maxima have been observed on the dependences of some kinetic parameters of the thermovulcanization reaction on polymer blend composition.     

溴化丁基橡胶的热可逆共价交联

利用季铵化反应的热可逆特性,采用含有叔胺官能团的聚合物替代传统交联剂,研究了溴化丁基橡胶(BIIR)的交联反应活性及交联的热可逆性.结果表明,硫化温度和硫化时间对交联BIIR的凝胶含量有显著影响,在160 ℃×30 min的硫化条件下,交联剂呈现出较高的交联活性;不同温度下的转矩测定和190 ℃二次热压的塑性流动证实交联BIIR具备热塑加工性.     

Properties and morphology of crosslinked butadiene-acrylonitrile rubber and polysulphide rubber (NBR/TM) blends

Blending of thermodynamically immiscible butadiene–acrylonitrile rubber (NBR) and polysulphide rubber (TM) results in superior performance materials as regards solvent resistance, and shows some unusual relations between the composition and properties of the blends obtained. Improved performance after vulcanization is probably because of better interphase bonding, resulting from NBR–TM co-crosslinking. Occurrence of such bonding and its role in amelioration of some of the blends’ properties are discussed in this paper. The effect of TM concentration and crosslinking system on vulcanization state and behaviour is studied by application of chemical, mechanical and thermal methods. © 1998 SCI.     

高乙烯基聚丁二烯交联四丙氟橡胶性能的研究

采用不同量的高乙烯基聚丁二烯橡胶(HVBR)作为助交联剂,以过氧化二异丙苯引发交联四丙氟橡胶(FEPM),制备具有新型交联结构的FEPM/HVBR共混胶,同时表征该橡胶的硫化特性、物理性能、断面形貌、溶胀度和热性能。结果表明:随着HVBR用量的增大,共混胶的硬度和拉伸强度增大,拉断伸长率降低,加工安全性和流动性变优;共混胶的玻璃化温度与FEPM接近,且随着HVBR用量的增大,共混胶的玻璃化温度升高,耐热性能提高。