Interpenetrating-network formation during electron beam crosslinking of an unsaturated polyester-1,6-hexanediol diacrylate monomer system

The progress of electron beam (EB) crosslinking of an unsaturated polyester (UP)-hexanediol diacrylate (HDDA) monomer mixture was monitored by different methods. The gel content measured by solvent extraction was found rather high already at relatively low doses. The physical changes in the system during crosslinking were followed by differential scanning calorimetry (DSC) and dielectric spectroscopy. The DSC results show a shift in T_g with increasing irradiation dose and the beginning of thermal reaction at about 150°C. By irradiation the peaks of the dielectric spectra are broadened and the oscillator strength is reduced. By FTIR analysis it was found that the double bond content of the unsaturated polyester changes only slightly while that of the monomer decreases steeply with the dose. Based on these results the formation of interpenetrating network is probable in the case of UP/HDDA system.