Enhanceing antifungal activity of starch-based wood adhesive by Larch bio-oil

Abstract

In order to enhance the antifungal activity of wood products with starch-based wood adhesive (SWA), the Larch bio-oil was involved in the synthetic of SWA as a fungicide. The chemical compositions of Larch bio-oil and its antifungal effects against three common molds (Aspergillus niger, Penicillium citrinum and Trichoderma viride) were evaluated, and the comparison of antifungal activity, basic characteristics and chemical structure between bio-oil starch-based wood adhesive (BSWA) and SWA were conducted. The results indicated that the Larch bio-oil was composed of considerable amounts of phenols, ketones, aldehydes and organic acids (total 71.0 %) and exhibited excellent antifungal activity against the tested molds with the inhibition zone diameters of 14.28–19.67 mm and the minimum inhibitory concentration of 25 %. Compared with SWA, the antifungal rating of BSWA was improved, and the bonding strength of BSWA increased by 53.4 % while the curing temperature decreased by 18.0 %. These improvements were supported by the changes in the chemical structure of adhesive after adding Larch bio-oil. In comparison with the SWA, the peaks of C2, C3, C5 and C6 of the starch molecular structure of BSWA in the 13C NMR analysis all decreased, while the peaks of C1 and C4 both increased. The results confirmed that Larch bio-oil could be used as a renewable substitute fungicide for SWA.