9th Annual Student Colloquium & Poster Session.
Real time Wide-Angle X-ray Scattering (WAXS) measurements during cyclic tensile tests at high strain rates (from 8 s'1 to 280 s1) and at room temperature on crosslinked Natural Rubber (NR) 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. This
critical time is characterized by a change in the growth kinetics of the crystallites in the plan
orthogonal to the traction axis. The orientation of the crystallites is not significantly modified by high velocities of deformation.