Green Epoxidized Niepa Seed Oil for Toughening Epoxy Resin: An Insight Into Viscoelastic, Mechanical, Thermal and Adhesive Properties

Non‐edible vegetable oil‐based epoxy resins have gained major attention as they can partially replace the commercial epoxy resins. This work focuses on optimizing the epoxidation conditions of Niepa ( Quassia indica ) seed oil (N), which is a renewable, inedible, and non‐toxic resource. Subsequently, the influence of epoxidized Niepa seed oil (EN) on the mechanical, viscoelastic, adhesive, and thermal properties of epoxy (E) is evaluated. Nuclear magnetic resonance (NMR) and titrimetric studies revealed that the optimum condition for in situ epoxidation of N is 60°C for 10 h (selectivity 76.6%). Further, E/EN blends were prepared at varying compositions. Differential scanning calorimetry (DSC) studies indicated a reduction in the enthalpy of curing with increasing EN content. Dynamic mechanical analysis (DMA) revealed a slight reduction in cross‐link density and glass transition temperature ( T g ) with higher EN content. The rise in tan δ reflects the superior damping properties of the blends. Despite the reduction in tensile properties of blends, the impact strength and lap shear strength enhanced to 34.8 kJ/m 2 (324%) and 10 MPa (82%), respectively, for E/EN (85/15). The findings indicate that EN is a potential candidate to overcome the brittleness of epoxy resin and thereby enhance its application in the field of adhesives.