Models of multivinyl free radical photopolymerization kinetics

Models for predicting multivinyl free radical photopolymerization that incorporate diffusion controlled propagation and termination are discussed. One model focuses on spatial effects by incorporating heat and mass transfer in photopolymerizing films. Temperature, species concentrations, e.g., oxygen and initiator, and light intensity are varied as a function of both time and depth. Specifically, the effect of using polychromatic initiation on oxygen inhibition was investigated. The model predicts that by utilizing initiating radiation of two distinct wavelengths, it is possible to overcome oxygen inhibition and achieve complete cure. The second model incorporates chain length dependent termination (CLDT) and chain transfer to polymer (CTP) in a homogenous, polymerizing system. Specifically, how CTP affects the polymerization rate (Rp), the reaction diffusion coefficient, the scaling relationship between polymerization rate and initiation rate (Ri), i.e., Rp∝Riα, and the transition from CLDT to reaction diffusion controlled termination was investigated. The model predicts that, in general, at low double bond conversion, CTP inclusion decreases the reaction diffusion coefficient and increases the polymerization rate. Additionally, increasing the CTP rate decreases the double bond conversion both at which the termination mechanism begins to transition from CLDT to reaction diffusion controlled termination and at which reaction diffusion controlled termination becomes the dominant termination mechanism. The model provides more insight into the termination mechanism and complex polymerization behavior.