Sustainable resin development for the strategic upcycling of waste fly ash into high-performance polymer composites

Recently, there has been an increasing demand for Eco-friendly resins as alternatives to petroleum-based products to achieve carbon neutrality and reduce greenhouse gas emissions. Simultaneously, effective waste management is essential for promoting environmental sustainability. This study aims to address both issues by presenting the development of a novel high-performance Eco-friendly resin and its application in fly ash (FA)-based composites. The Eco-friendly resin was synthesized with sodium lignosulfonate, polyvinyl alcohol, and citric acid (CA), a crosslinker. The optimal resin properties were determined by varying the CA concentration and crosslinking conditions, and esterification was performed. This reaction resulted in significant improvements of the esterified resin in tensile strength (127.8%), Young's modulus (36.6%), toughness (1237.8%), elongation (420.4%), and hydrophobicity (44.3%), compared to the hydrogen-bonded resin. The FA was modified using polydopamine, a biomimetic self-adhesive polymer, to enhance interfacial compatibility and facilitate the formation of covalent ester crosslinks with the matrix, alongside physical interactions. Subsequently, chemically modified FA (M-FA) with different concentrations was blended with this resin to produce composites. Notably, the incorporation of only 0.1 wt.% of M-FA into the lignin-based resin resulted in a significant increase in tensile strength (38.5%), elongation at break (12.5%), Young’s modulus (27.6%), and toughness (65.4%) compared to the unmodified FA(U-FA) composites. While conventional approaches have historically shown poor FA–polymer composites, our novel approach presents a transformative opportunity to convert fly ash into high-performance composite materials, defined by a tensile strength exceeding 140 MPa and thermal stability comparable to engineering plastics.