Abstract
Dimethacrylate-based resins cured using a photoinitiator system are widely used as matrices in dental restorative composites. In this work, the thermal degradation of copolymers based on urethane dimethacrylate (UDMA) and bis-phenol A glycidyl dimethacrylate (BisGMA) were investigated by thermogravimetric analysis. Different weight ratios (100/0, 70/30, 50/50, 30/70 and 0/100) between the UDMA and BisGMA comonomers were employed. The camphorquinone – ethyl-4-dimethylaminobenzoate photoinitiator system was used. The degradation of copolymers occurs in three steps, contrarily to two steps for UDMA homopolymer and a single step for BisGMA homopolymer. Activation energies of the degradation processes were calculated using differential and integral isoconversional methods. The influence of copolymers composition on the activation energy as a function of the degradation conversion degree was studied. Keywords: thermal degradation, dimethacrylate copolymers, UDMA/BisGMA