Sustainable Biobased Composites: Fumaric Acid-Based Epoxy Resin Synthesis and Modified Natural Waste Reinforcements

Abstract

The increasing demand for sustainable alternatives to petroleum-based polymers has accelerated the development of biocomposites to mitigate environmental impact. In this study, a novel bio-based epoxy resin (EFA) was synthesized via the reaction of fumaric acid (FA) and epichlorohydrin (ECH), and characterized using FT-IR, 1H NMR, viscosity, mass spectrometry, and epoxy group analysis. Apricot kernel shell (APKSh), an agricultural waste, was used as a natural reinforcement, modified with citric acid (CA) and levulinic acid (LA) to improve interfacial compatibility. Composites were produced with filler contents ranging from 5 to 30 wt% and tested for FT-IR, SEM, TGA, DMA, mechanical, thermal, and surface properties. The 15 wt% CA-modified composite exhibited a tensile strength of 105.7 MPa, an elastic modulus (e-modulus) of 8.7 GPa, and a Shore D hardness of 80, representing up to 222 % improvement in tensile strength and 107 % improvement in hardness compared to the neat ER-EFA (7:3 weight ratio). The LA-APKSh composites showed a char residue of 26.9 % at 800 degrees C and a Tg value of 106.01 degrees C. Contact angle (C.A.) measurements revealed enhanced hydrophobicity, with values exceeding 99.6 degrees for CAAPKSh composites. The weight gain data in seawater indicated that all composites had higher values compared to the neat ER-EFA matrix (7:3 weight ratio). ANOVA analysis highlighted the influence of filler type and content on composite properties. This study presents a promising approach to developing high-performance, eco-friendly epoxy composites using chemically modified lignocellulosic waste.