The copolymerization of styrene and maleic anhydride initiated by peroxides of isotactic polypropylene

A monomer mixture of styrene (St) and maleic anhydride (MA) was grafted on isotactic polypropylene (PP) powder at 80 degrees C in benzene. During that process ungrafted copolymer is formed at the same time. The initiators are peroxide groups formed on the surface of polypropylene (PP) by ozonization or by gamma-irradiation. The grafting of the two monomers on PP as well as forming of unbound copolymer depend on the quality and quantity of the initiator structure type. Two types of hydroperoxidic groups are present on the surface of the oxidized polypropylene (OPP)-associated hydroperoxides (AHP) and isolated hydroperoxides (IHP). The results allow us to conclude that the partial transformation of AHP into IHP proceeds during the polymerization caused by components of the system or by temperature as well as by the iodometric reduction. A reversible transformation of IHP during a long storage of OPP is also possible. The alternatives to the mechanism of formation and reactions of radicals in this system are discussed. The results are compared to those obtained earlier in emulsion polymerization of styrene with a redox activator of initiator.