Effect of polythiourethane hardener modification on the behaviour of epoxy resin

Polythiourethanes based on oligomeric polymercaptans were employed as curing agent of epoxy resin. The epoxy matrices, in the form of castings, were characterized for their mechanical properties such as tensile strength, elongation at break and unnotched Charpy impact strength as per ISO methods. Mechanical studies indicated that the incorporation of polythiourethane into epoxy resin improves the toughness and flexibility with reduction in tensile strength for samples cured at ambient conditions and influences the mechanical and thermal properties according to its percentage content for samples cured at 130°C. The high increase of impact strength was explained by the development of two-phase morphology during the cure process. The results of this study indicate that both the stoichiometry of the curing mixture and the initial thermal condition are of critical importance in governing the curing mechanism, structure of the network, morphology and the final properties of epoxy/polythiourethane compositions.