The effect of different modification conditions on the efficiency of poplar wood epoxidation and the physical properties of the product

Wood modification with epoxy compounds, such as glycidyl methacrylate, could result in less moisture absorption and dimensional changes due to reduction in the number of hydroxyl groups and cell wall bulking. It is likely that change in the conditions of modification reaction would have a favorable effect on the physical properties by increasing the hydroxyl group’s substitution. To determine the optimal modification condition with glycidyl methacrylate, samples were modified at different concentrations (10, 20 and 30%), temperatures (90, 120 and 150°C) and times (8, 16 and 24 hours). Based on spectrum analysis, decrease of hydroxyl groups intensity and increase of carbonyl groups intensity confirmed cell wall modification with glycidyl methacrylate. Cell wall bulking and hydrophobing due to modification led to a reduction in porosity and free water adsorption. According to the results of soaking-drying cyclic test, increase of glycidyl methacrylate concentration led to the reaction with more number of hydroxyl groups, and higher temperature and longer duration of modification reaction also led to an increase in the reactivity of the epoxy groups with the wood cell wall. The higher temperature of reaction led to maintenance of weight gain due to modification, via formation of a more stable structure against hydrolysis. Scanning electron microscopic images confirmed cell wall swelling and polymerization of glycidyl methacrylate in wood cavities. In a general conclusion, it can be claimed that the concentration of 20%, the temperature of 150°C and the time of 16 hours are the optimal conditions for modification with glycidyl methacrylate.