Mechanochemical Reactions in Black-Filled SBR Vulcanizates under Large Deformation

Abstract

Abstract Mechanochemical degradation of black-filled SBR's at large deformation was studied in relation to abrasion. Deformation of rubbers caused bond scission and reduced the crosslink density; however, subsequent free radical reactions reconstructed the network structure in a short time to some extents depending on the strain. The extent of crosslink recovery was larger with larger strains. As a consequence, the loss in crosslink density showed a peak when plotted against the strain. When rubber was deformed by repeatedly passing through a narrow gap of a two-roll mill, the crosslink density was raised appreciably above the original level after a small number of passes. Surprisingly, the rubber could become plastic-like while the crosslink density was maintained high. All of these results matched well with the characteristic phenomena observed in abrasion of rubbers, e.g., the varying appearance of wear with severity, the worn surface and debris prone to be oxidized, and the bimodal size distribution of debris. It was strongly suggested that mechanochemical degradation participated in abrasion in a wide range of severity.