On the mechanism of sulfur behavior in rubber compounds
On the mechanism of sulfur behavior in rubber compounds
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DOI：
10.1080/00222349808220461
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发表时间：
1998-01-01
期刊：
影响因子：
--
通讯作者：
Jurkowska, B
中科院分区：
文献类型：
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作者：
Jurkowski, B;Jurkowska, B
矿物硫是一种广泛使用的成分，在硫化过程中在橡胶链之间形成交联。在复合过程中，硫在40摄氏度和70摄氏度之间的温度下的高弹性状态促进了其颗粒的伸长，然后将这些细而弱的针状物破碎成碎片。这增加了颗粒的表面积，并且在熔融后，为硫向橡胶基质中的强烈扩散创造了条件，这有助于使硫在固化橡胶中的分布均匀。硫相对均匀地分布在橡胶化合物的本体中。然而，在橡胶化合物的储存过程中，在其表面上观察到一薄层硫（霜）。这会在心理上影响加工，并对使用中的硫化橡胶性能产生影响。在40摄氏度以下，随着橡胶化合物储存时间的延长，起霜硫的浓度会增加。当温度超过42摄氏度时，硫会逐渐消失。硫/硬脂酸的低共熔合金应该在从在高于42 ℃的温度下储存的橡胶化合物的表面消失起重要作用。这是因为该低共熔物的熔点（约46 ℃）非常接近于观察到起霜机理变化的熔点。在此条件下，硫作为低共熔物处于熔融状态;因此，它可以扩散到聚合物基质中。如果含有硫、促进剂、硬脂酸和氧化锌的固化体系的熔融颗粒在配混的最后阶段在橡胶基质内相遇，则可能形成低共熔物。
Mineral sulfur is a widely used ingredient to form cross-links between the rubber chains in the vulcanization process. During compounding, a high elastic state of sulfur at temperatures between 40 degrees C and 70 degrees C promotes elongation of its particles and, next, breaking these thin and weak needles into pieces. This increases the surface area of particles and, after melting, creates conditions for intensive diffusion of sulfur into the rubber matrix, which helps to equalize the distribution of sulfur in cured rubber. Sulfur is relatively uniformly distributed in the bulk of rubber compound. However, during storage of rubber compounds, a thin layer of sulfur is observed on their surface (a bloom). This detrimentally affects processing and has an influence on cured rubber properties in use. Up to 40 degrees C, the concentration of bloomed sulfur increases as the storage time of a rubber compound is prolonged. For temperatures above 42 degrees C, bloomed sulfur disappears gradually. The eutectic alloy of sulfur/stearic acid should play an important role in the disappearance of a bloom layer from the surface of a rubber compound stored at a temperature above 42 degrees C. This is because the melting point for this eutectic, about 46 degrees C, is very close to that at which the change in mechanism of blooming was noticed. Under this condition, sulfur, as a eutectic, is in a molten state; due to this, it can diffuse into the polymer matrix. Formation of a eutectic is possible if molten particles of the curing system, containing sulfur, accelerator(s), stearic acid, and zinc oxide, will meet each inside the rubber matrix during the last stage of compounding.