Wood-derived phenol novolaks and their wood/epoxy biocomposites

Abstract

Guaiacol novolak (GCN) and wood-tar creosote novolak (WCN) were synthesized by the reactions of wood-derived guaiacol and creosote with formalin, respectively, and used as hardeners of sorbitol polyglycidyl ether (SPE). Thermal and mechanical properties of the cured resins (SPE-GCN and SPE-WCN) and their biocomposites with wood flour (WF) were compared with those of the materials prepared by using a petroleum-based phenol novolak (PN). Although tan δ peak temperatures of SPE-GCN and SPE-WCN were lower than that of SPE-PN, that (58.5-70.8°C) of SPE-GCN/WF(40-50 wt %) was higher than that (56.6-57.0°C) of SPE-PN/WF(40-50 wt %). Tensile moduli of all the biocomposites increased by the addition of WF, while tensile strengths were rather reduced. When the biocomposites with the same WF content were compared, tensile modulus of SPE-GCN/WF was higher than that of SPE-PN/WF. The 5% weight loss temperatures (346-291°C) of SPE-GCN and SPE-GCN/WF were comparable to those (338-284°C) of SPE-PN and SPE-PN/WF.