Study on the synthesis of bio-based epoxy curing agent derived from myrcene and castor oil and the properties of the cured products

Abstract

Two novel bio-based epoxy curing agents derived from myrcene (MMY) and castor oil (CMMY) were prepared, respectively. Their chemical structures were confirmed by Fourier transform infrared spectrometry (FTIR) and ¹H nuclear magnetic resonance (¹HNMR). The two curing agents were used to cure a commercial epoxy resin (E-51). The MMY-cured epoxy resin had very poor toughness while the CMMY-cured epoxy resin had low strength, so the two curing agents were mixed at different weight ratios to form new curing agents for the E-51 epoxy resin. The tensile strength, impact strength, dynamic mechanical properties, thermal stability, micro-morphology of fracture surfaces and gel content of the cured epoxies were all investigated. The curing behaviors of the cured epoxies were studied by differential scanning calorimetry (DSC). Results show that the elongation at break is increased and the tensile strength and glass transition temperature are decreased with increasing weight ratio of CMMY, while the impact strength is increased gradually. The initial degradation temperatures of all the cured epoxy resins were above 367 °C. The gel contents of the epoxy resins cured with the mixed curing agents were above 87%. The activation energies for the systems with MMY and CMMY were 75.90 and 67.69 kJ mol⁻¹, respectively.