Grafting dual polar monomers onto hydroperoxidized polypropylene with the assistant of supercritical carbon dioxide

A hydroperoxidized polypropylene (HPP) was obtained by oxidizing PP porous particle in solid phase, followed by impregnating dual polar monomers of pentaerythritol triacrylate (PETA) and styrene (St) into the HPP with the aid of supercritical carbon dioxide (scCO₂). Then, HPP was used as polymerization initiators and PETA/St were grafted onto microporous PP backbone in water medium. Effects of hydroperoxidation temperature, time, oxidant dosage and PP diameter on hydroperoxides concentration and G _p and G _e were illustrated systematically. Besides, effects of scCO₂ swell time, pressure, monomers concentration and ratio, grafting reaction time and temperature on G _p and G _e were also examined. Results showed that G _p can be easily controlled by changing process conditions; G _e was observed to be greater than 90% in most of the cases. Gel content of grafted samples was also determined. The structures and thermal properties of grafted copolymers were characterized through FTIR, SEM, TGA and DSC.