Modelling of the kinetics of the supercritical CO2 assisted grafting of maleic anhydride onto isotactic polypropylene in the solid state

This work aimed at comparing and modelling the kinetics of the free radical grafting of maleic anhydride onto polypropylene (PP) in the solid state with and without supercritical CO2 (scCO2). The kinetics of the decomposition of dicumyl peroxide (DCP) in scCO2 and in N2 was first studied. The one in scCO2 could be described by kd=1.32×1014×exp(-139.3kJmol-1/RT). Without scCO2 the overall grafting reaction rate was controlled, at least partly, by diffusion whereas with scCO2 it was controlled mainly by the grafting reaction itself. Based on the experimental results, the following general kinetic model for the free radical grafting in scCO2 was developed: Rg=3.35×1012×exp(-114.5kJmol-1/RT) [I]0.99 [M]0.97(molL-1s-1).