Influence of Treatment Parameters on Beech Wood (Fagus sylvatica) Modified with Polyethylene Glycol and Various Carboxylic Acids

In this current study, beech wood (Fagus sylvatica) was modified by cross-linking via esterification with combinations of polyethylene glycol (PEG) 400 and various carboxylic acids. Promising combinations (1,2,3,4-butanetetracarboxylic acid (BTCA)/PEG400; citric acid (CA)/PEG400; malic acid (MA)/PEG400) were examined in previous studies. The goal of this study was the optimisation of the treatment. The use of a catalyst, the concentration of the chemicals and the curing conditions were varied. The weight percentage gain (WPG), bulking and anti-swelling efficiency (ASE) after leaching in water were used to evaluate the success of modification. Optimal results were achieved with a curing temperature of 160 °C. Without the addition of PEG, the WPG and bulking values were lower. The use of sodium hypophosphite monohydrate (SHP) as a catalyst had a positive effect only on the combination of BTCA/PEG400. Variations of concentrations usually had a higher impact on WPG and bulking than on ASE. The combination of MA/PEG 400 generally showed lower values.