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

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.