Bio-based vanillyl alcohol epoxy thermoset with high mechanical properties and its applications for high- performance natural fiber-reinforced composites

Abstract

Abstract With the massive usage of fossil-based resources and net-zero missions, developing bio-based epoxy resin and sustainable composites with excellent comprehensive properties from biomass resources as an alternative to commercial petroleum-based epoxy is still a crucial challenge. Herein, taking advantage of the mono and diepoxy cross-linking network structure, a lignin-derived novel cross-linked vanillyl alcohol epoxy (VAE) thermoset-containing mono and di (m&d) epoxy structure is prepared by the epoxidation of the vanillyl alcohol, followed by curing with hardener. The synthesized m&dVAE containing mono and di-epoxidized (m&d) aromatic rings, when cured with 4, 4´-diaminodiphenyl methane (DDM) hardener, exhibits higher record tensile strength ~ 124.0 ± 8.43 MPa and tensile modulus ~ 2.88 ± 0.35 GPa compared to a commercial petroleum-based epoxy, diglycidyl ether bisphenol A (DGEBA) thermoset. Additionally, it demonstrated higher adhesion shear strength (~ 19.16 ± 0.58 MPa) with cellulose nanofibers film than DGEBA. Further, the synthesized m&dVAE-DDM resins are used for bio-based natural fiber-reinforced composites for the first time. The green composite possesses excellent flexural strength of ~ 203.72 ± 2.08 MPa and stiffness of ~ 11.58 ± 0.38 GPa than the petroleum-based thermoset composite. Moreover, the green composite showed good hydrophobicity and an excellent heat-resistant index of 144.4°C. The m&dVAE resin can be an alternative to petroleum-based resins, and its environment-friendly green composite could be a promising candidate to replace synthetic materials for high-performance structural applications.