Thermal, mechanical properties and morphology of epoxy resins modified with light pyrolysis natural rubber

Abstract

Instead of using traditional functional liquid rubbers in toughening epoxy, light pyrolysis natural rubber (LPNR) obtained from scrap rubber was introduced to improve the toughness of cured epoxy resins. Epoxy blends were prepared by physically mixing the epoxy resins with various concentrations of LPNR. The structure, thermal, mechanical properties and morphology of the epoxy blends were investigated by Fourier transform infrared spectroscopy, differential scanning calorimetry, dynamic mechanical analysis, impact behavior, and scanning electron microscopy. It was found that the inclusion of 5 phr LPNR reached the maximum value in impact strength of the modified epoxies and the presence of LPNR enables the epoxy resins to fracture in a pattern more akin to ductile materials than in case of the neat epoxy which shows features of brittle rupture. The agglomeration of rubber particles decreased the toughness of epoxy resins modified with more LPNR. Meanwhile, the nearly unchanged glass transition temperature of LPNR epoxy samples illustrated weak interfacial adhesion existed between the rubber phase and epoxy matrix due to low compatibility and feeble combination between them. The thermal stability of modified epoxy resins went down because of the existence of LPNR domains inside the matrix. Overall, the LPNR should be further investigated to improve its compatibility and reinforce its combination with the epoxy resins to become a particularly efficient toughening agent because of its cheaper resource and contribution to environmental protection.