Study on the impregnation quality of rubberwood (Hevea brasiliensisMüll. Arg.) and English oak (Quercus roburL.) sawn veneers after treatment with 1,3-dimethylol-4,5- dihydroxyethyleneurea (DMDHEU)

Abstract

AbstractThe efficacy of chemical wood modification is closely related to the permeability of the wood species and the cell wall deposition of the reagent, causing a permanent swelling (“bulking effect”). This study aimed to analyze how rubberwood (Hevea brasiliensisMüll. Arg.) and English oak (Quercus roburL.) may be affected by chemical wood modification, although they are known to show either variations in permeability or being less permeable. Thin clear veneers were treated with 1,3-dimethylol-4,5- dihydroxyethyleneurea (DMDHEU) which resulted in significantly reduced moisture-induced swelling and increased the resistance to static and dynamic indentation loads. The results evidenced significantly lower liquid uptakes in English oak compared to rubberwood, which directly affected the weight percent gains (WPGs) and restricted the range for potential improvements of the material properties. Surprisingly, rubberwood showed a lower cell wall bulking, which, in comparison with English oak, indicated less DMDHEU monomers entering the cell walls and rather being located in the cell lumens. Atypical for treatments with cell wall penetration chemicals, no further decrease in maximum swelling (SM) was detected with increasing bulking in rubberwood specimens. English oak showed higher variations in DMDHEU distribution within treated veneers and between earlywood and latewood areas, effecting a less homogeneous performance.