An experimental study of the mechanically induced crystallization in filled natural rubber: relevant variables, kinetics and effect of loading history

Modelling crystallization under stretch is a key topic for fatigue design of rubber-like antivibration parts. Nevertheless, the industrial compounds used exhibit dissipative visco-elastic behaviour that complicates splitting between mechanical and time effects on the phase change and its kinetic, and thus the characterization and modelling of the phenomenon. In this study, we consider an industrial recipe for load/unload tension tests over a range of strain rates leading to non-equilibrium cases, and a multi-relaxation cyclic test combining static and monotonic steps (ANH). A systematic analysis of the triplet \{strain, stress, crystallinity ratio\} and their derivatives was applied, taking advantage of well resolved in-situ synchrotron measurements and providing insights into crystallization and melting kinetics and effects of loading history on these ones. The results obtained for this fully formulated material and various loads representative of service conditions provide a precious database to challenge the existing mechanical models aiming at describing the cristallinity index and crystallization/melting kinetics.