Kinetic and heat transfer modeling of rubber blends' sulfur vulcanization with N‐t‐butylbenzothiazole‐sulfenamide and N,N‐di‐t‐butylbenzothiazole‐sulfenamide

Vulcanization kinetics and heat transfer for various blends of natural (NR) and polybutadiene (BR) rubber were studied simultaneously using a mechanistic approach when developing vulcanization model kinetics. Rubber process analyzer (RPA), dynamic scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FTIR) methods were used for the study. The model reaction scheme was based on one of the best possible proposed individual reaction mechanisms. Molecular modeling was applied to distinguish between the reactivity of chemically similar species. The kinetics of N‐t‐butylbenzothiazole‐sulfenamide (TBBS) and N,N‐di‐t‐butylbenzothiazole‐sulfenamide (TBSI) were treated separately using FTIR experiment data, and then incorporated in a model suitable for two‐accelerator vulcanization. The proposed model quite well describes the thermal equilibration during the induction period despite a few simplifications. During cure and over‐cure periods the course of vulcanization was described using a rigorous kinetic model. Physical and chemical model parameters were calculated from experimental data. Average heat transfer coefficient minimum during induction period was found to be at a weight ratio of BR and NR 1 : 1. The activation energy of significant reactions between rubber and other species was found to vary linearly with vulcanization compound composition.