Features of strain-induced crystallization of natural rubber revealed by experiments and simulations

Abstract

Understanding the strain-induced crystallization (SIC) mechanism of natural rubber (NR) is a prerequisite for comprehending the reinforcement mechanism of NR and for designing new high-performance rubber materials. With the help of new technologies that have enabled more accurate experimental measurement of the microstructure and the use of molecular simulations that can be applied to probe structural changes during stretching in real time, some interesting results have been found. For instance, even at high strains, a very large fraction of the unoriented amorphous phase still remains in the stretched sample with homogeneous or heterogeneous networks. In addition, the onset strain of SIC in peroxide-cured NR decreases with an increasing crosslinking density, while sulfur-cured NR is independent of the crosslinking density, which cannot be explained by conventional theories. The presence of nanofillers, entanglements, non-rubber components and pseudoend-linked networks also results in abnormal phenomena of SIC. Both experimental measurements and molecular simulations were applied to probe the strain-induced crystallization (SIC) of natural rubber in real time, and some interesting results have been found. A very large fraction of unoriented amorphous phase remains, even at high strains. The onset strain of SIC in peroxide-cured NR decreases with increasing crosslinking density, while that in sulfur-cured NR is independent of crosslinking density. This difference may be caused by different network structures. Nanofillers, entanglements, non-rubber components and pseudoend-linked networks also result in abnormal SIC phenomena.