A mesoscopic computer model for reinforcement in filled and strain-crystallizing elastomer networks

To study reinforcement, particularly in Natural Rubber, a model developed for filled rubber is integrated into a model for elastomers which involves strain-induced crystallization (SIC). The combined model considers both the structures of strain-induced crystallites and the filler morphology in the rubber matrix. The focus here is on the investigation of 2D-networks. At small deformations, the Payne effect can be observed for model networks containing a fraction of filler larger than the percolation threshold. It is caused by breaking of filler-filler bonds. At larger deformations, the stress of both crystallizing and non-crystallizing model networks is amplified by the inclusion of filler. The effect is enhanced if the filler is finely dispersed. The combined model is extended by a critical free energy density for the rupture of model polymer chains. This rupture criterion determines whether the tensile strength and elongation at break of crystallizing or non-crystallizing networks are higher. Despite discrepancies for unfilled networks, the behavior of the tensile strength dependent on filler content approaches the experimental observations for finely dispersed filler.