Modelling and measuring UV cure kinetics of thick dimethacrylate samples
Résumé
The UV cure kinetics of thick samples composed of a dimethacrylate oligomer, a photobleaching initiator, and in the presence of oxygen are modeled and measured. First, the temporal and spatial variation of initiator concentration and the resulting variation of intensity with depth are calculated using previous results determined from thin samples. Then cure kinetics at different depths are predicted using a model that accounts for a changing concentration of free and trapped radicals. Thereby, the model includes variation in the extent of unimolecular and bimolecular termination as the reaction proceeds. This is different from the classic steady-state assumption involving only bimolecular termination. The model's calculated results are compared with the experimental results measured by transmitted near-FTIR for a number of thick samples of varying thickness exposed to differing intensities and having differing initiator concentrations. The model's predictions are in good agreement with the experimental results.