Development and characterization of an epoxy-based hybrid polymer composite modified with cashew nut shell liquid, castor oil, and aluminium nanoparticles

While conventional epoxy resins exhibit excellent mechanical properties, their inherent brittleness, lack of sustainable content, and moderate thermal performance limit their application in eco-friendly lightweight engineering. To address these limitations, this study aims to develop a sustainable hybrid polymer matrix based on epoxy matrix with the addition of 2.5 wt.% aluminium nanoparticles and additives of bio-based materials, Cashew Nut Shell Liquid (CNSL) and castor oil. Different formulations were developed and tested for mechanical, thermal and flammability properties. The tensile strength of the nano-reinforced ternary hybrid composite was the highest (51.3 MPa) while Young’s Modulus was the highest (3280 MPa) in comparison with neat epoxy (38.05 MPa and 537 MPa respectively). The flexural strength of the system reinforced with aluminium reached a maximum value of 18.11 MPa and for the ternary blend with nano-fillers it was 1.59 GPa. The impact resistance was enhanced from 1.8 J/cm 2 for neat epoxy to 2.1 J/cm 2 (neat epoxy/castor oil). The Shore-D hardness of the neat epoxy was similar, at 80, while the reinforced castor-oil epoxy measured 79. Fourier Transform InfraRed (FTIR) spectroscopy validated the good chemical interaction and crosslinking between epoxy, bio-oils and aluminium nanoparticles. Thermogravimetric analysis also showed high thermal stability as temperature of decomposition reached 369°C and char yield of 46%. Limiting Oxygen Index (LOI) was between 19 and 24 for the formulations. The outcomes showed that bio-derived oils and aluminium nanoparticles, when synergistically incorporated into the epoxy-based composites, improved the mechanical properties, thermal resistance and structural integrity of the composites.