Photo-crosslinked acrylates degradation kinetics

A series of crosslinked polyurethane acrylate solids with glass transition temperatures ranging from -49 to +65 A degrees C was prepared by photopolymerization of specially formulated solvent-free resins. The kinetics of thermooxidative and thermal (in N-2) degradation of these crosslinked acrylate networks at temperatures ranging from 100 to 400 A degrees C was studied as a function of crosslink density using thermogravimetry. The polyacrylate network degradation rate decreased with the increase of crosslink density, while apparent activation energy of degradation increased. Polyacrylate thermal stability increase with crosslinking was explained by decreased rate of oxygen and volatile products diffusion and/or slowing of depolymerization due to increased radical recombination rate, and decreased chain segments mobility in systems with higher crosslink density.