ELASTIC PROPERTIES OF THERMOSETS IN GLASSY STATE

The Young's modulus E and Poisson's ratio nu of various thermosets, in cluding 6 amine crosslinked epoxies, one anhydride crosslinked epoxy, one styrene crosslinked polyester and one styrene crosslinked vinylest er, were determined from tensile tests in the 220-393 K temperature ra nge and 1.6710(-4)-1,6710(-2) s-1 strain rate range. The bulk (B) and shear (G) modulus were calculated from E and nu. Some observations abo ut structure-property relationships can be derived from these data and their comparison ones relative to linear polymers. B appears to depen d essentially of the cohesion and packing density and does not depend, practically, of temperature and strain rate. In contrast, G depends s harply of the local molecular mobility, this latter being affected by an antiplasticization mechanism. The Poisson's ratio seems to be syste matically higher for thermosets than for linear polymers.