Kinetics of the benzoyl peroxide/amine initiated free-radical polymerization of dental dimethacrylate monomers: Experimental studies and mathematical modeling for TEGDMA and bis-EMA

The kinetics of the benzoyl peroxide/amine initiated free-radical cross-linking polymerization of dimethacrylate monomers used as dental materials was studied. The monomers examined were (t)riethylene glycol dimethacrylate (TEGDMA) and ethoxylated bisphenol A glycol dimethacrylate (Bis-EMA). As co-initiator to the benzoyl peroxide (BPO) the new amine 4-(N,N-dimethylamino)phenethyl alcohol was used. The polymerization rate vs time for several initial initiator concentrations was measured using differential scanning calorimetry. Differences in the polymerization kinetics of the two monomers are discussed in connection with the chemical structure of dimethacrylates Furthermore, a mathematical model was developed to simulate the BPO/amine initiated free-radical polymerization of dimethacrylate monomers. In the elementary reaction mechanism besides initiation, propagation, and termination reactions, also inhibition, primary radical termination, radical trapping, and secondary initiator chain transfer reactions were included. Diffusion-controlled phenomena on the termination, propagation, and initiation reactions were incorporated into the model based on theoretical equations and the free-volume theory. Theoretical simulation results were in good agreement with the experimental data for all different initial initiator concentrations studied.