Moisture Sorption and Accelerated Weathering of Acetylated and Methacrylated Aspen

Wood cell-wall modification with acetic anhydride, lumen fill with methyl methacrylate, and a combination of these two treatments were studied for their effectiveness in reducing the rate of moisture sorption and the degradative effects of accelerated weathering. Compared to that of untreated wood, the rate of moisture sorption of aspen acetylated to 18 weight-percent gain was greatly reduced as was the extent of swelling in liquid water; erosion due to accelerated weathering was reduced 50%. Methyl methacrylate treatment slightly decreased the rate of swelling in liquid water but did not reduce the extent of swelling. This lumen-fill treatment decreased erosion caused by accelerated weathering about 40%, compared to the erosion of untreated wood. A combined treatment of acetylation followed by methacrylate impregnation was the most effective in reducing the rate and extent of swelling and reducing erosion caused by accelerated weathering (85%). Chemical analysis before and after accelerated weathering showed that ultraviolet degradation caused a large loss of surface lignin and xylose (from xylans) in control specimens. Both acetylation and methacrylate treatments, or a combination of the two, reduced the loss of surface lignin with subsequent reduction in weathering. Acetylation, especially at 18 weight-percent gain, reduced the loss of xylans during accelerated weathering