Elucidation of segmental relaxations of silica-filled cis-polybutadiene rubber composites

There has been a lot of interest in characterizing polymer chain dynamics of rubber compounds because it is thought to underpin the exceptional mechanical properties of composites. We studied the effect of precipitated silica on segmental mobility of cis-polybutadiene rubber by using differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). It was found that the calorimetric glass and melting transitions of silica-filled master batch materials were essentially identical to those of the gum rubber, showing no dependence of silica loading and silane treatment. And, we observed in calorimetric measurement a change in the melting transition step for the vulcanizates. The results were correlated to the change of chemical crosslinks caused by various factors filler agglomeration and adsorption effect that tended to decrease chemical crosslink density and silane modification increased it. The DMA results demonstrated that the second peak in loss modulus versus temperature curve for the quenched vulcanizates was assigned to melting peak, and this peak disappeared at a slow cooling rate, which coincided well with DSC results. Moreover, crystalline parts constrained amorphous regions such that the glass transition temperature was raised for the cooled vulcanizates with high chemical crosslinks.     

炭黑和白炭黑填充硫化胶的湿摩擦差异性分析

研究不同负荷和速度下炭黑和白炭黑填充硫化胶的湿摩擦因数,并对其摩损表面进行了扫描电子显微镜和透射电镜表征。结果表明：炭黑填充硫化胶的湿摩擦因数随着速度的增大呈线性下降,随着负荷的增大略有降低,而白炭黑填充硫化胶的湿摩擦因数随着速度的增大呈非线性下降,随着负荷的增大先迅速下降后缓慢降低;白炭黑填充硫化胶摩擦面橡胶膜较薄,裸露白炭黑粒子,过渡区摩擦力较大,不能忽略;炭黑填充硫化胶表面的橡胶膜厚度较大,表面炭黑粒子被橡胶大分子覆盖,过渡区摩擦力小,可以忽略。