Combination of Chemical Modification and Densification Processes to Improve the Sorption and Dimensional Stability of Wood

Due to the limited availability of durable tropical timber species, the development and production of chemically modified wood materials are expanding. Past research has investigated chemical reactions between the hydroxyl groups of wood and carboxylic acid anhydrides. Tropical species exhibit excellent durability, mechanical properties, and low water absorption, making it difficult for domestic species to compete with them. Therefore, this study employed a combination of chemical modification processes (acetylation and propionylation) and densification on two of the most widespread domestic species: European beech (Fagus sylvatica L.) and Norway spruce (Picea abies (L.) H. Karst). The modified samples were compared in terms of water-related properties, specifically sorption and dimensional stability. Both chemical modification methods, when combined with densification, positively influenced the monitored sorption and dimensional characteristics compared to non-densified samples. Unlike the reference samples, the modified domestic species exhibited water-related properties and dimensional stability comparable to the selected exotic species, Jatoba (Hymenaea courbaril). While Jatoba samples generally showed higher density values, densified propionylated beech and reference spruce were statistically comparable, and densified reference beech actually surpassed the density values significantly.