Mathematical modeling and parameter estimation for 1,6-Hexanediol diacrylate photopolymerization with bifunctional initiator

A dynamic model is proposed for photopolymerization of 1,6-hexanediol diacrylate (HDDA) using bifunctional initiator bis-acylphosphine oxide (BAPO). The proposed model accounts for branching, backbiting and cyclization reactions, and for diffusion-dependent reaction rates during photopolymerization. The proposed model contains 40 adjustable kinetic and free-volume parameters. Experimental data available for parameter estimation are vinyl group conversions obtained using a variety of light intensities and exposure times, and monomer conversions for three experiments. Systematic parameter ranking and estimation is used to evaluate the influence of phenomena included in the model on the quality of the fit. Estimation and ranking results indicate that branching, backbiting, and cyclization reactions have important influences on conversion. Reactions involving two large molecules and propagation reactions become diffusion-dependent. Incorporating diffusion-dependent initiator efficiency results in improved model predictions.