Bonding of acetylated wood

Abstract

Through the modification of wood, various properties can be altered by chemical, physical or mechanical processes that influence the bonding quality and workability of gluing systems. This is evident for adhesion, pressing time, curing and glue line properties. Further, testing methods need to be evaluated on their applicability for determining the bonding quality of modified woods. In this paper, laboratory test results of non-load-bearing-laminated acetylated products are presented. The results are evaluated and discussed in respect to chemical composition, ultra-structure and other properties altered by the acetylation process.

Quasi-static and fatigue performance of bonded acetylated rubberwood (Hevea brasiliensis, Müll. Arg.)

“…MUF and PRF on the other hand retained strong adhesion in wet conditions, and the wood fails in wet condition leading to a higher WFP compared to PUR bonded samples. These results are comparable with previous studies on other wood species where the WFP of wood bonded with PUR is low (Bongers et al 2016;Kläusler et al 2014a), but high for MUF and PRF in Fig. 3 Average weight percent gain of acetylated rubberwood (*treatment is significantly different at p ≤ 0.05).…”

“…The tests on acetylated samples in dry conditions did not reveal any significant differences neither in TSS nor in WFP to the values of the unmodified samples for any of the three tested adhesives. For PUR, which requires a minimum moisture content of about 6-8% for good bonding performance (Beaud et al 2006), the lower moisture sorption of acetylated rubberwood did not impair the bonding performance tested in dry conditions, which is in agreement with previous studies (Bongers et al 2016;Vick et al 1993). Therefore, the bonding performance of the tested adhesives and of wood is not influenced by acetylation in dry condition (Vick and Rowell 1990).…”

“…Hereby, DMF leads to pronounced swelling of wood, which is thought to make more OH-groups of wood accessible to the glue, leading to higher adhesion of the glue to wood. The acetylation process in this study included the use of DMF, contrary to previous studies on bonding of acetylated wood, where treatment with acetic anhydride was performed without the use of solvents (Bongers et al 2016;Brandon et al 2005;Vick and Rowell 1990). In these studies, the WFP was not improved for PUR bonded wood.…”

“…They found that for all types of PUR adhesives, acetylated wood performed better when compared to unmodified wood in dry and wet conditions. However, the WFP of unmodified and acetylated wood bonded with PUR has been reported to be low in wet condition (Bongers et al 2016;Vick and Rowell 1990). Bonded acetylated wood also performed well with the use of resorcinol-formaldehyde adhesive for both planed and un-planed surfaces, while epoxy adhesives performed better with unplaned acetylated wood surfaces in both dry and wet conditions (Frihart et al 2017).…”

“…In wet condition, PUR, MUF and PRF performed better with increasing level of acetylation. Bongers et al (2016) evaluated the performance of six one-component PUR adhesives as well as MUF and polyvinyl acetate (PVAc). They found that for all types of PUR adhesives, acetylated wood performed better when compared to unmodified wood in dry and wet conditions.…”