Semi-interpenetrating novolac-epoxy thermoset polymer networks derived from plant biomass

Abstract

Bio-based phenol-formaldehyde polymer (BioNovolac) was developed by reacting molar excess of bio-oil/phenol with formaldehyde in acidic medium. Glycidyl 3,5-diglycidoxybenzoate (GDGB), was prepared by direct glycidylation of α-resorcylic acid (RA), a naturally occurring phenolic monomer. GDGB was crosslinked in the presence of BioNovolac by anionic polymerization. Fourier transform infrared spectroscopy (FTIR) confirmed the formation of semi-interpenetrating polymer networks. The glass transition temperature and moduli of bio-based crosslinked systems were observed to increase with increasing GDGB content. Active chain density and mass retention measured by dynamic mechanical analysis (DMA) and Soxhlet extraction, respectively, indicated a high crosslink density of the cured networks. Scanning electron microscopy (SEM) images depicted the homogeneity of the bulk phase. The preparation of bio-based epoxy-novolac thermoset network resulted in reduced consumption of petroleum-based chemicals.