Prediction of thick rubber compression vulcanization process with improved vulcanization kinetics model considering temperature dependence and its initial state

Reasonable setting of the vulcanization process parameters is crucial for the molding quality of rubber products. The issue of non-uniform distribution of vulcanization degree induced by time-dependent temperature fields (typical non-isothermal vulcanization) frequently occurs in thick rubber components. However, the existing vulcanization kinetics models virtually lack sufficient description of this non-isothermal state, making it difficult to accurately and effectively determine the optimal vulcanization process conditions. In this study, a vulcanization kinetics model was developed incorporating temperature-dependent factors to accurately describe the kinetic behavior across both stages of molded vulcanization: the curing phase and the cooling phase. A thick rubber column (76 mm in diameter, 34 mm in thickness) was used to validate the accuracy of the proposed vulcanization kinetics model. Temperature test data at selected locations throughout the rubber column, microstructure, and cross-linking density were measured using thermocouples, scanning electron microscope, and shore rubber hardness tester, respectively. In addition, the proposed vulcanization kinetics model was implemented with user-defined function in Fluent software to simulate the temperature distribution and the curing degree inside the rubber column. Comparison between experimental and simulation results demonstrated that the proposed vulcanization kinetics model accurately predicts rubber curing behavior under both isothermal and non-isothermal conditions. This capability supports the design and optimization of vulcanization processes for thick rubber products.