Bio-Based Epoxy Resins Derived from Eugenol with High Glass Transition Temperatures as Substitutes for DGEBA

Abstract

Epoxy resins (EPs) are crucial for high-performance applications like lightweight materials, due to their excellent properties. However, the commonly used diglycidyl ether of bisphenol A (DGEBA) has two major disadvantages: it is synthesized mainly from petrochemicals and includes the health concerning bisphenol A. Eugenol is a bio-based aromatic compound that can be modified into di- or triglycidyl ether. Through investigations four monomers are obtained based on eugenol and crosslinked with two curing agents isophorone diamine and 4,4′-diaminodiphenyl sulfone to compare the properties of the resulting EPs with references containing DGEBA. Using new synthesis routes, the bio-content of the monomers can be increased up to 94 wt%. Intramolecular cyclization occurs if a hydroxy group is in ortho-position to the glycidyl ether group. The crosslinking conditions of the bio-based monomers are comparable to or lower than those of DGEBA. The eugenol-based triglycidyl monomers exhibit very high glass transition temperatures of up to 271 °C, almost 50 °C above the reference value, which can enable their use for lightweight construction such as matrices for fiber-reinforced plastics. The char content of all bio-based EPs after pyrolysis is significantly higher in comparison to the references, which may have a favorable effect on fire resistance.