The grafting of maleic anhydride onto a granular polypropylene (PP) using supercritical CO2 as a solvent and swelling agent was studied to prepare granular PP-g-MAH polymers The factors affecting the graft degree of PP

such as the monomer content

initiator content

reaction temperature and reaction pressure were discussed The maximum graft degree of PP with MAH in supercritical CO2 medium was 5.23％ under the optimal reaction conditions at 125℃ and 15 MPa for 5 h．By using the superefitical CO2 technique the operation of grafting reaction and separation of products became simple and easy to deal with．The formation of PP-g-MAH grafting copolymer was evidenced by FTIR measurements An absorption peak at 1720.6 cm-1 assigned to the stretching vibration of carbonyl groups was observed．DSC results indicated that the grafting gave almost no influence of Tg values

but may increase the crystallinity of PP.