Preparation and properties of biocomposites composed of sorbitol‐based epoxy resin, tung oil‐pyrogallol resin, and wood flour

The biocomposites composed of sorbitol polyglycidyl ether (SPE), tung oil‐pyrogallol resin (TPG), and wood flour (WF) were prepared by the compression molding at 190°C, and their thermal and mechanical properties were investigated in detail. The epoxy/hydroxy ratio was fixed to 1/1 in the curing reaction of SPE and TPG, based on the fact that the degree of addition of pyrogallol to each tung oil molecule for the TPG used as a flexible bio‐based hardener is evaluated to be 2.3 by 1 H‐NMR method. The SPE‐TPG/WF biocomposites showed much higher storage moduli than SPE‐TPG did, although tan δ peak temperatures of the biocomposites (44.5–45.6°C) were a little lower than that of SPE‐TPG (53.5°C). Tensile moduli of the biocomposites increased with an increase of WF content in the range of 0–50 wt %. Furthermore, the biocomposites had a little higher tensile strength than the cured neat resin did. Field emission‐scanning electron microscopy analysis of the biocomposites revealed that WF is tightly incorporated into the crosslinked epoxy resins. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013