FUNCTIONALIZATION OF POLYPROPYLENE VIA MELT MIXING

Grafting of maleic anhydride (MAH) onto isotactic polypropylene (PP) w as performed by melt mixing in a laboratory-scale internal mixer with the addition of dicumyl peroxide (DCP) as an initiator. The efficiency of the graft reaction (estimated by use of Fourier-transform infra-re d spectroscopy) tends to decrease with increasing MAH or DCP content; the optimal composition for the present reaction system appeared to be at a low DCP level and a moderate MAH loading. Concurrent with the gr afting reaction, PP undergoes significant chain scission as indicated by the decrease in mixing torque and supported by the dynamic rheologi cal evidence. The first addition of MAH to the reaction mixture enhanc ed the DCP-initiated chain scission; upon further addition of MAH, the scission reaction became less severe. These observations were explain ed in terms of competition between chain transfer/beta scission and bi molecular coupling of radical intermediates.