Dual Grafting of MAH/styrene onto Polypropylene Using Supercritical CO_(2) Fluid

Free-radical dual grafting of maleic anhydride(MAH) and styrene(St) onto granular polypropylene(PP) using supercritical CO_(2) as a solvent and swelling agent has been studied and PP-g-(MAH-St) prepared. The effect of molar ratio of monomers, swelling temperature and time, reaction time and pressure on the grafting density are discussed. It is found that the St as a co-monomer in the grafting reaction system could (significantly) enhance the grafting density of PP for MAH and St on PP. The maximum grafting density for PP-g-(MAH-St) in supercritical CO_(2) fluid under optimal reaction conditions was 10.58%, two times that for PP-g-MAH. The process is simpler than regular graft polymerization processes. The structures and properties of the graft copolymers were characterized by FTIR and DSC. The results indicate that styrene branch chains reduces the T_(m) of PP from 158 ℃ to 154 ℃.