Numerical analysis of a reactive extrusion process. Part I: Kinetics study on grafting of vinylsilane to polyethylene

For controlling a reactive extrusion process in the subsequent study, the model equations of reaction kinetics and shear viscosity were studied. We focused on a free radical reaction between the molten polyethylene and vinylsilane. The kinetics model was expressed as a reaction rate equation with an apparent rate constant. The shear dependent of reacted polyethylene was formulated by employing the modified Cross model proposed in our early study; In addition, the average molecular weight was considered to correlate the shear viscosity with the reaction kinetics, leading to a series of rheo-kinetics formulas. The experiments were carried out in a specific batch mixer suitably designed for sampling in arbitrary periods. Their reaction conversions, molecular weight distributions, and shear viscosity were measured, respectively, with an induced coupled plasma (ICP) emission spectrochemical analyzer, a high temperature gel permeation chromatography (GPC), and a capillary rheometer. Determining the parameters in each model, a simulator is set to investigate an engineering extrusion process.