Thermomechanical performances of epoxy complex with castor oil-based polyglycidyl ethers as efficient toughness and strength agents

The aim of the work is to develop two functionalized castor oil-based polyglycidyl ethers containing benzene rings by ring-opening etherification and alkylation reaction, respectively: phenoxy castor oil-based polyglycidyl ether (POCOGE) and phenolic castor oil-based polyglycidyl ether (PCOGE). Castor oil-based polyglycidyl ethers were introduced into E-51, which is a common type of bisphenol A epoxy resin. The thermomechanical performances of the polymer blends were evaluated. The addition of the synthetic castor oil-based polyglycidyl ethers showed an enhancement of E-51 in both toughness and flexibility without sacrificing bending strength. The tensile strength reached 81.0 MPa and 86.4 MPa, which were 26.5% and 34.9% higher compared to that of pure E-51. Meanwhile, the impact strength reached 28.1 kJ m⁻² and 19.4 kJ m⁻², an increase of 147% and 70.3%, respectively, compared with E-51. Scanning Electron Microscope (SEM) graphics exhibited those cured polymers had ductile fracture. The non-isothermal curing kinetics of different curing systems were analyzed by Málek's method and conformed to the Šesták–Berggren SB(m,n) model. This study aims to address the inadequate stiffness of bio-based epoxy resins and extend the scope of bio-based epoxy resins with versatile functionality.