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