A crosslinking kinetic model considering reversion effect with verification and its application in thick rubber vulcanization process

Abstract

Vulcanization is crucial for rubber product processing. The phenomenon of “over-cure on the outside surface and under-cure at the inside position” often occurs for thick rubber products; however, very few suitable kinetic models exist to describe the reversion stage of rubber curing under non-isothermal conditions currently. In this study, we proposed a piecewise nonlinear crosslinking kinetic model that could reproduce the kinetic responses of three vulcanization stages (induction, curing, and reversion stage). A thick rubber sphere with a diameter of 50 mm was utilized to verify the accuracy of the crosslinking kinetic model. The test data distribution of temperature and crosslinking density at different points of the rubber sphere were measured using thermocouples and low-field nuclear magnetic resonance tester, respectively. The crosslinking kinetic model was implemented with user-defined subroutines in Abaqus/Standard (UVARM and USDFLD). The distribution of temperature and degree of curing of the rubber sphere were simulated. Comparison between test data and simulation data indicated that the proposed piecewise nonlinear crosslinking kinetic model can predict the rubber vulcanization kinetic behavior under both isothermal and non-isothermal conditions, which can help design and optimize the vulcanization process for thick rubber articles.