Temperature Dependence of Strain-Induced Crystallization in Silica- and Carbon Black-Filled Natural Rubber Compounds

The results of strain-induced crystallization (SIC) studies on natural rubber compounds containing different amounts of carbon black and silica are reported. Two-dimensional wide-angle X-ray diffraction (2D WAXD) experiments were performed to quantify the degree of SIC at ambient and enlarged temperatures. The influence of temperature and filler system on the degree of crystallinity of natural rubber was investigated, since the estimated temperatures in truck tire treads are in the range 60–80 °C. Interestingly, the degree of crystallinity for silica-filled natural rubber compounds was commonly at least similar or higher compared to carbon black-filled compounds with identical filler mass fraction. In addition, it was demonstrated that the temperature dependence of natural rubber compounds containing silica and carbon black is also similar. In both cases the SIC disappeared slightly above 100 °C. Hence, it was concluded that the SIC behavior is most likely not the decisive factor for the different abrasion resistance of silica- and carbon black-reinforced natural rubber compounds for truck tire treads. This is an important insight considering the rising demand for sustainable rubber compounds for truck tire treads with low CO2 emissions as well as reduced abrasion.