Beech wood modification based on in situ esterification with sorbitol and citric acid

Abstract

Abstract In this study, modification of European beech wood ( Fagus sylvatica ) through in situ esterification of sorbitol and citric acid (SorCA) was investigated at two curing temperatures, 140 and 160 °C. In order to determine the optimum condition for modification, an aqueous solution of SorCA at varying concentrations was evaluated (10, 20, 30, and 55% w/w). Physical, mechanical, chemical, and durability properties of the modified wood were examined. Results have disclosed that among different SorCA concentrations, treatment with SorCA at 30% w/w was considered as the optimum concentration independent of the curing temperature. Under these conditions, anti-swelling efficiency increased to approx. 55% and modulus of elasticity increased slightly with approx. 9% in comparison with untreated wood. Decay resistance against white-rot ( Trametes versicolor ), brown-rot ( Coniphora puteana ), and soft-rotting microfungi classified the SorCA-30%-modified wood as very durable. In addition, thermogravimetric study evidenced that SorCA 30%-modified wood has a lower thermal decomposition temperature in comparison with untreated wood/wood control by 20 °C difference, indicating that the SorCA-modified wood possibly has fire-retardant properties. However, due to the acidic properties of the SorCA solution, modulus of rupture (MOR) and mainly work to maximum load in bending decreased considerably.