Abstract
Rubberwood is widely planted for latex production. At the cessation of latex yield it becomes a viable timber source in the wood industry. While good bonding performance of rubberwood has been reported, quantitative information to support this statement is missing. In this study, the tensile shear strength (TSS) and wood failure percentage (WFP) of unmodified and acetylated rubberwood in both wet and dry conditions were examined. Three frequently used adhesives were selected: one-component polyurethane (1C PUR), melamine-urea-formaldehyde (MUF), and phenol-resorcinol-formaldehyde (PRF). Furthermore, fatigue behaviour was analysed for PRF-bonded samples by cyclic loading. Results showed that in dry state, the TSS and WFP of acetylated rubberwood is comparable to the unmodified samples for all adhesives. In wet condition, the performance of bonded rubberwood was improved by acetylation. Cyclic loading revealed comparable fatigue behaviour of bonded unmodified and acetylated rubberwood. This investigation provides first quantitative information on the performance of bonded rubberwood, which can be a valuable input for the production of laminated timber products for structural purposes.
Highlights
Rubberwood is a hardwood species that has been known initially as an agricultural product established mainly for latex production
As in the present study, a reduced sample size is used for testing lap shear strength in contrast to the dimensions specified by EN 302-1:2013, the effect of downscaling the sample size on tensile shear strength (TSS) was tested with beech wood using 1C PUR
This study provides a quantification of bonding performance of acetylated rubberwood in terms of TSS and fracture mode for dry and wet conditions (A1, A2)
Summary
Rubberwood is a hardwood species that has been known initially as an agricultural product established mainly for latex production. As the latex production declines or ceases, rubberwood is used as timber due to its good woodworking properties such as machining, sawing, or turning, and appealing aesthetics. It was found that in some cases, in dry condition, bonding strength decreased with increasing levels of acetylation Adhesives such as PUR, MUF and PRF were capable of forming strong and durable bonds with acetylated wood, showing no change compared to the performance of unmodified wood. 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. Bonded acetylated wood 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)
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