Evaluation of Photo-polymerization Kinetics by Means of Transmittance Measurements

Polymeric resins are widely used for dental reconstruction, and most of them use the camphorquinone as activator of the polymerization reaction, through the absorption of light at a defined wavelength range (400÷460 nm). During the photopolymerization curing, transparency of these resins change, and transmittance variation was detected by photodiode and bolometer measurements. This change can be used as an index of the reaction rate, so the kinetic parameter k (reaction rate) was evaluated from transmittance data by means of nonlinear regression. The relation between k and the light intensity impinging the resin sample is thus obtained, revealing the presence of two different polymerization reactions at two different intensity ranges. Results can be used to predict the most suited curing times for different light intensities, even for different materials, as ceramics.