In situ WAXS dynamic study of strain induced crystallization kinetics of synthetic and natural rubber

Real time Wide-Angle X-ray Scattering (WAXS) measurements during cyclic tensile tests at high strain rates (from 8 s(-1) to 280 s(-1)) and at room temperature on crosslinked Natural Rubber (NR) and Synthetic Rubber (IR) are performed thanks to the development of a specific homemade device. From the observed influence of the frequency on the crystallization index at the maximum sample elongation, a characteristic crystallization time is deduced. Furthermore, an adjustable stroboscopic system allows obtaining the crystalline properties not only at the maximum sample elongation but along the complete cycle. The experiments enabled us to extract a critical time of 50 msec below which the macromolecules cannot appreciably crystallize. A comparative study on NR and IR shows that these materials exhibit very similar strain-induced crystallization kinetics. This trend is very different than these one observed during conventional test, i.e. at law strain rate. These results should be explained by the high degree of supercooling reached by both materials.