The liquid like transitions of unsaturated polyester resin by conductivity measurements

The temperature curves of dc current on liquid unsaturated polyester (UP) resins diluted by various amounts of styrene exibit several straight-line segments. From this the activation energies, glass and liquid-like transition temperatures have been evaluated. The transitions have been conformed by thermally stimulated discharge (TSD) measurements. The current intensity and transitions have been varied by diluting with styrene and by irradiation in the (pre)gel state. Another liquid-liquid like transitions found in polarization measurements, which is masked in TSD by S -transition, has been verified by viscosity measurements. The liquid like transitions correspond to the thermal activated disintegration of local ordered structures, which were well documented in the inherently heterogeneous UP resin system.