Curing of urethane dimetracrylate composites: A glass transition study

Abstract

Urethane dimethacrylate thermosets (UDMA) and their composites (PICN) were cured under varying polymerization pressures (1–3500 bars) and the resulting materials were characterized mainly by dynamic mechanical analysis (DMA) to measure their glass transition. In the case of PICN, glass transition displays an optimum in the middle pressure range (1000–2000 bars), which is linked to the conversion degree of polymerization process as measured by near infrared (NIR) spectrometry whereas it displays hyperbolic increase for UDMA networks. The results were discussed using classical theories used for describing the glass transition of networks. For samples post-cured at 160 °C during 1 h, the glass transition of undercured samples (1–1000 bars and P > 3000 bars) is shown to increase in link with possible post-curing. Reversely, the Tg of the most cured samples (polymerization pressure about 2000 bars) decreases which was attributed to the possible thermal decomposition. The glass transition temperature is here tentatively proposed a marker of the network architecture for samples varying by their processing (curing, post-curing) conditions and possibly their degradation level.