Electron beam curing of aliphatic unsaturated polyesters. I. Mechanistic study on converting to pressure-sensitive adhesives

Aliphatic unsaturated polyesters (UPEs) mixed with N,N-diethylaminoethyl methacrylate (DEAEMA) were convertible by electron beam irradiation to soft solids of high peeling strength. Double bond conversions, gel contents, molecular weight distributions, and crosslinking densities of the irradiated mixtures were studied in comparison with those of UPE-vinyl acetate mixtures, which gave very low peel strength on irradiation. The latter system started gel formation even at earlier stages of irradiation and had higher cross-linking densities as a result of copolymerization between polyester and monomer double bonds. In contrast, the UPE-DEAEMA system exhibited slow gel formation with predominant conversion of monomer double bonds, indicating formation of graft copolymers. This system also had lower crosslinking densities than the other system. Therefore, it was concluded that the pressure-sensitive adhesive nature of the electron-beam-cured UPE-DEAEMA mixtures could be attributed to the formation of flexible graft polymers entangled in a loosely crosslinked network. (C) 2003 Wiley Periodicals, Inc.