Mechanism and kinetics of grafting of polypropylene by water-soluble monomers in emulsion

Oxidized isotactic polypropylene powder was grafted at 30 °C in aqueous emulsion with water-soluble monomers such as acrylic acid and acrylamide. The decomposition of the polypropylene -O-O- groups, initiating the graft polymerization, proceeds due mainly to the effect of the activator used, viz. a chelate of iron(II), and is favoured by the monomer and the necessarily present water-insoluble liquid phase. The grafting reaction order with respect to the concentration of the water-soluble monomer is 2 and higher. A mechanism and kinetics are suggested for the polypropylene grafting by these water-soluble monomers, involving the concept of presence of long-living radicals bonded to the solid polypropylene phase.