INTERNAL ANTIPLASTICIZATION IN COPOLYMER AND TERPOLYMER NETWORKS BASED ON DIEPOXIDES, DIAMINES AND MONOAMINES

Seven epoxy networks based on diglycidyl ether of bisphenol A, isophorone diamine and trimethylcyclo-hexylamine, and differing in the amine/epoxy molar ratio and/or in the monoamine/diamine molar ratio, were studied by tensile and compressive tests, ultrasonic wave propagation and thermomechanical spectroscopy. It appears that any structural modification leading to a decrease in the glass transition temperatures induces an increase in the elastic modulus in the glassy state, above the β-relaxation. This so-called internal antiplasticization phenomenon cannot be linked to change in volumetric properties, as previously proposed in the literature, but rather to the effect of crosslinks on the local mobility. © 1990.