Effects of chain transfer agent on the electron beam-induced graft polymerization of glycidyl methacrylate in emulsion phase

Abstract

The graft polymerization of glycidyl methacrylate from irradiated polyethylene/polypropylene (PE/PP) in the presence of the chain transfer agent 4-cyano-4-((phenylcarbonothioyl)thio) pentanoic acid (CPPA) was studied at 40 °C using pre-irradiation grafting technique. Free radical active sites on polyethylene/polypropylene were formed by electron beam irradiation in nitrogen atmosphere and dry ice temperature. Compared to the conventional grafting method, addition of the chain transfer agent resulted in lower amount of grafted poly(glycidyl methacrylate) (PGMA) on the PE/PP trunk polymer. The calculated degree of grafting increased with increment in absorbed dose and reaction time but decreased with increasing glycidyl methacrylate concentration, at fixed monomer to CPPA ratio, and amount of CPPA. An apparent first-order dependence of conversion on monomer concentration was observed. The free poly(glycidyl methacrylate) that was formed in the polymerization mixture during grafting in the presence of CPPA had Mn which increased with reaction time and polydispersity index (PDI) values less than 2. NMR analysis of the PGMA homopolymer indicates the presence of dithiobenzoate group from CPPA at one end of the polymer chain. The pristine and grafted trunk polymers were characterized with FTIR, TGA, and SEM-EDX.