Kinetics of Strain-Induced Crystallization in Natural Rubber Studied by WAXD: Dynamic and Impact Tensile Experiments

Abstract

The time-dependence of strain-induced crystallization in cross-linked natural rubber was studied using synchrotron wide-angle X-ray diffraction (WAXD) with an unprecedented time resolution in the ms range. In-situ dynamic mechanical tests and tensile impact tests were carried out. In tensile impact tests, consisting of a strain step within less than 10 ms, it was found that roughly half of the crystallization process was complete within less than 5 ms, provided the strain is large enough. Afterward, crystallization proceeded on a time scale of a few seconds. This implies that under dynamic loading at frequencies which are typically encountered in the application of rubbers, the degree of crystallinity is considerably lower than under equilibrium conditions. This was directly confirmed by in situ dynamic cyclic experiments at a frequency of approximately 1 Hz. Since crystallization is a major factor contributing to the outstanding mechanical properties of natural rubber, these findings can aid in the interpretation and prediction of the frequency-dependence of mechanical properties.

Temperature dependence of strain-induced crystallization in natural rubber: On the presence of different crystallite populations

“…The time of the different temperature steps is thus long enough to consider that the equilibrium state is reached. This is consistent with a recent study of Brüning [29] that showed that the rate of melting is extremely fast (around 10 msec), at least much higher than the heating rate of the present study. The same trend is observed for L 200 , as shown on Fig.…”

Kinetics of strain-induced crystallization in natural rubber: A diffusion-controlled rate law

“…While temperature and strain are the main parameters governing the degree of crystallinity, its time-dependence is especially M A N U S C R I P T A C C E P T E D ACCEPTED MANUSCRIPT critical in dynamic loading scenarios. On time scales shorter than a few seconds, due to the finite crystallization kinetics the crystalline microstructure in NR significantly deviates from what is suggested by quasistatic tensile experiments [3].…”

Structural Changes of Gluten/Glycerol Plastics under Dry and Moist Conditions and during Tensile Tests

“…36,37 A home-made tensile rig was used to carry out both mechanical deformation and small/wide angle X-ray scattering 38,39 . The tensile rig was mounted on top of a hexapod for fine sample alignment.…”