A Kinetic Model for Accelerated Sulfur Vulcanization for Natural Rubber

摘要

A fundamental kinetic model has been developed for the sulfur vulcanization of natural rubbe with a 2-4 morpholinothio-benothiazole sulfenamide (MBS) accelerator.The model was developed using population balance methods that explicity acknowledge the polysulfidic nature of the crosslinks and various reactive intermediates.This approach allows for a more faithful incorporation of the underlying molecular mechanisms that control the vulcanization process.For the MBS vulcanization system we need a total of nine rate constants:two to describe the including scorch delay,two to describe the regeneration and degradation of the accelerator,and efficiently and robustly determined from isothermal oscillating disk rheometer cure data at three different sulfur/accelerator concentrations.The kinetic model can quantitatively predict the complete cure response including induction,curing and the reversion for a complete range of compositions;moreover,the population balance model can be readily extended to also include also the concentration of all the intermediates of different polysulfidic lengths-important information that is difficult to measure experimentally.The level and detail of information obtained from the model can be used effectively to understand the cure and post-cure behavior of an accelerated vulcanization system and to determine the optimal amounts of accelerator,sulfur,activator and other ingredients needed to design the formulation for a particular engineering application.