Abstract
Chemical modification of wood can improve its dimensional stability and resistance to biological degradation and moisture, but modification can also create a new surface for bonding. Acetylation of wood results in the loss of hydroxyl groups, making the wood more hydrophobic and reduces its ability to hydrogen-bond with the adhesive. In contrast, reacting wood with butylene oxide or propylene oxide lowers swelling of wood in water but does not reduce the number of free hydroxyl groups. The hydrogen bonding model of adhesion would favor the oxide-modified wood over the acetylated wood for higher bond strengths. The effectiveness of adhesion to wood modified with acetic anhydride, propylene oxide, or butylene oxides was evaluated by measuring the dry and wet shear strength, and the percentage wood failure of bond specimens. Unmodified and modified wood specimens of yellow-poplar (Liriodendron tulipifera) were bonded with four adhesives (epoxy, emulsion polymer isocyanate, melamine formaldehyde, and resorcinol formaldehyde) selected on the basis of their sensitivity in bonding to acetylated wood. The importance of the hydrogen bonding model could not be fully determined in these experiments because even though the propylene oxide and butylene oxide modifications enhanced wood failure percentages, they had made the wood substantially weaker. Except for the emulsion polymer isocyanate, all adhesives gave stronger bonds with the acetylated wood than the untreated wood especially during water-saturated conditions.
Keywords
Acetylation,
dimensional stability,
adhesives,
testing,
Liriodendron tulipifera,
wood,
biodegradation,
deterioration,
hydroxyl group,
propylene oxide,
acetic anhydride,
butylene oxide,
moisture content,
swelling,
bond strength,
strength,
acetylated wood,
yellow-poplar,
bonding,
modified wood,
chemical modification of wood
Citation
Brandon, Rishawn; Ibach, Rebecca E.; Frihart, Charles R. 2005. Effects of chemically modified wood on bond durability. Wood Adhesives 2005 : November 2-4, 2005 ... San Diego, California, USA. Madison, WI : Forest Products Society, 2005: ISBN: 1892529459: pages 111-114.
