Thermal property measurements during curing of thermoset resins using steady periodic conditions

Variation of thermal diffusivity and specific heat of a general-purpose epoxy during curing was investigated experimentally. The thermoset materials are particularly difficult to characterize during their polymerization on the one hand because of the presence of exothermic chemical reactions and on the other hand because their thermophysical properties depend both on the temperature and on the degree of cure. Thanks to a method in periodic mode associated with very sensitive thermal sensors, one could separate and measure the variations of thermal diffusivity with temperature and degree of cure during the thermoset polymerisation. In addition, a heat capacity analysis was performed during the cure using a temperature modulated calorimeter. Thermal diffusivity measurements show a non linear increase of more than 100% during the cure of an epoxy/glass fiber composite while heat capacity changes are less than 10%.