Viscoelastic properties and transitions during thermal and UV cure of a methacrylate resin

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Abstract
The solidification behavior of a dimethacrylate system during UV and thermal cure at temperatures from the Tg of the monomer (T) to above the ultimate Tg of the polymer (T) is investigated using torsional dynamic mechanical analysis. Gelation and vitrification times are quantified using several criteria for the transitions, and the data are presented as a function of cure temperature in TTT diagrams. The influence of cure method and temperature on the mechanical properties, degree of conversion, and gel content of the cured samples is discussed. The results show that gelation occurs before or at the same time as vitrification at all temperatures, including T. With UV cure, gelation generally occurred within seconds, whereas the properties continued to develop for minutes or hours afterwards. The method of cure was found to influence the properties of the cured material. When prepared above T, the UV cured material had a higher Tg, a higher crosslink density, and a higher degree of conversion than the thermally cured material.