New Insights Into Strain-Induced Crystallization and Temperature-Induced Crystallization of Un-Vulcanized Natural and Synthetic Rubber: Extended Chain Versus Chain Folding

New insights into the strain-induced crystallization (SIC) and temperature-induced crystallization (TIC) of un-vulcanized natural rubber (NR) and peroxide vulcanized natural rubber (PVNR) have been obtained by wide-angle X-ray diffraction (WAXD). The SIC samples were deformed at various temperatures (from -50 to 50 ˚C) in order to determine the effect of temperature on the crystallite structure. In the WAXD patterns, highly oriented sharp crystal reflections was observed for the SIC samples, whereas sharp rings without preferred orientation was observed for the TIC samples. A novel 2D method to calculate WAXD patterns have been used to obtain values for crystallite size, percent crystallinity, preferred orientation, as well as crystalline disorder. The crystallite sizes and volume increased with increasing temperature, but with a decrease in the number of crystals. The crystallite sizes were much larger for the TIC samples as compared to the SIC samples.