Bio-Based Epoxies

Abstract

Epoxy resins have been used as composite matrix materials for over half a century, enabling lightweight materials for a variety of applications. Their properties including high strength, chemical resistance, and ease of processing feature them as prime candidates for composite applications. Currently, high performance epoxy monomers are derived from non-renewable feedstocks, which presents a problem for future generations and technologies regarding sustainability. Many bio-based alternatives have been investigated, but properties fall short of high-performance industry standards due to a lack of appropriate chemical groups. Herein 3 bio-based epoxy monomers, with potential to replace high-performance standards, are compared against 3 petroleum derived industry standards. Industrial high performance aromatic diamine crystalline hardener is used to synthesise resin systems. Tensile, flexural and fracture toughness properties are investigated following ASTM standards. Beyond a practical investigation of the physical properties of these resins a comparison of chemical structure to mechanical properties is made. Free volume investigations using positron annihilation lifetime spectroscopy (PALS) were performed, and can be used to explain to some degree the observed properties of the resin systems.