TABLE OF CONTENTS In recent years a significant effort has been undertaken to evaluate the chemical and technological parameters associated with photopolymerisation. Many analytical techniques have been employed to monitor the cure reaction. Commonly used methods are rheology, chromatography, infrared spectroscopy, titration of functionalities, and mechanical property measurements. These methods have a high degree of sensitivity in either the initial or the final stage of polymerisation. They cannot be used, however, for in situ analysis of the curing process.
Sepe [1] has reviewed the application of differential photocalorimetry (DPC) to the analysis of photopolymers. DPC measures the heat of reaction absorbed on release by a material in photoinitiated reactions occurring when a material is exposed to ultraviolet (UV)/visible light in a temperature controlled environment or is used to measure the cure rate and degree of cure in photocurable polymers. The technique uses a dual-sample differential scanning calorimeter (DSC) to measure the heat of reaction of one or two samples as they are exposed to UV/visible light usually employing a high-range mercury arc lamp with a maximum intensity in the 200 400 nm range.
Since polymerisation processes are mainly exothermic reactions in which each additional chain formation step generates a defined amount of heat, the reaction process can be monitored directly and continuously. Combining DSC with an irradiation unit enables photoinitiated reactions to be studied. Cure data and extent of polymerisation are determined by chemical parameters such as photoinitiation, resin components, and additives and by technical parameters such as...
