Hydrosilylation of terminal double bonds in polypropylene through reactiveprocessing

The melt-phase hydrosilylation of terminal double bonds in polypropylene (P P) was investigated. The double bonds were generated by peroxide initiated degradation of PP in an extruder or a batch mixer. For this purpose, an org anic peroxide, Lupersol 101, was employed in concentrations of 0.5-5 wt%. A hydride-terminated polydimethylsiloxane was employed as a model substance to investigate the feasibility of hydrosilylating the terminal double bonds of the degraded polypropylene. Reactive processing experiments were carrie d out in a hot press, a batch mixer, and a single screw extruder. Two diffe rent reaction mechanisms were used to initiate the hydrosilylation reaction : a radical chain addition mechanism and a platinum catalyzed mechanism usi ng Karstedt's catalyst. For the radical mechanism, it was shown that cataly tic amounts of a peroxide could initiate the addition of silanes to the dou ble bonds of the degraded polypropylene. Furthermore, it was found that bot h reactions, degradation and hydrosilylation, could be performed simultaneo usly. For the catalytic mechanism, the required stabilization of the platin um colloid formed in this mechanism was accomplished by adding t-butylhydro peroxide as a cocatalyst. This melt-phase hydrosilylation route may be used to produce terminally functionalized polypropylenes, and a case study invo lving the terminal attachment of a styrene functionality was examined.