PHOTOCHEMICAL CROSS-LINKING OF POLYPROPYL ENE AND LOW-DENSITY POLYETHYLENE IN THE PRESENCE OF ACRYLIC-MONOMERS

The effects of diethyleneglycol diacrylate and butanediol diacrylate o n the efficiency of photo-induced cross-linking of PE and PP in the pr esence of benzophenone, 4-chlorobenzophenone, 4-tert-butylbenzophenone , and 4,4'-dimethylbenzophenone were studied. The efficiencies of phot ochemical and photo-induced processes were assessed on the basis of ge l fraction yields, conversion of the double bonds of the monomers, and initiator consumption rates. Quenching yields for quenching of the ex cited states of the initiators by the monomers were estimated using fl ash photolysis. It was found that diacrylates promote the cross-linkin g of PE and PP. The cross-linking efficiency was found to be controlle d by the donor-acceptor properties of the substituent in the molecule of benzophenone. Quenching of the excited states of initiator involvin g the formation of complex with a molecule of monomer was suggested as a mechanism accounting for this relationship. In PP, there was almost no difference in photoinitiating ability of benzophenone derivatives in the presence of the monomers. This may be due to reduced mobility o f the molecules of the monomers and initiators hindering the formation of complex between them during the life-time of the excited state of benzophenone.