Thermal Analysis of Photopolymerization

Photopolymerization processes used to be difficult to measure quantitatively by conventional techniques such as dilatometry, UV spectrometry, IR spectrometry and gravimetry. Using a special TA apparatus one can determine the fractional conversion according to the measurement of the polymerization heat. The advantages of measuring the photochemical reaction heat are as follows (1) photopolymerization analysis can be carried out on the system with the photosensitive resin produced from multi-component compounds (2) film-shaped samples can be measured using a high-sensitivity apparatus and (3) kinetic analysis of the polymerization heat can be performed directly. 

Both the degree of polymerization during radiation and after-polymerization after radiation can be calculated using the following equation  

The photopolymerization rate is dependent on the radiation wavelength and the ambient temperature and atmosphere. The properties of the polymer (e.g. glass transition temperature, T ) is also dependent on the radiation conditions (e.g. radiation time). The optimum conditions for photochemical reaction can therefore be determined by taking the above factors into full account. 

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