Effects of preservative-chemicals on the bonding strength of urea-formaldehyde adhesive in Bambusa vulgaris Schrad. ex J. C. Wendl. var. vulgaris hort. laminates

摘要

Timber over-exploitation has threatened traditional commercial species such that alternatives including bamboos are being sought especially in the wood composite industry. However, bamboo has short service-life, as it is bio-degradable. For its laminated boards to substitute those of timber, the strips would need preservative-treatment. The effect of conventional preservative (i.e., CCA) and extracts from an organic source (e.g., Erythrophleum suaveolens bark) on the bonding (i.e., shear) strength ofurea-formaldehyde (UF) resin in hot-pressed Bambusa vulgaris (green bamboo) laminates was examined. Sixty treated strips (200 mm long × 20 mm wide × 4.5 mm thick) were glued at their inner culm surfaces (i.e.,160 mm-glued and 40 mm-unglued portions).Untreated strips served as controls. Strips were paired at their gluelines and hot-pressed at 85 deg C and 15 Mb for 20 min.Bonding strengths at the glue-lines of the laminates were assessed using shear test (EN 13354: 2008). Bonding strengths of UF-resin laminates were weakened by the preservative chemicals, especially the inorganic type. Control laminates recorded greater mean shear strength (3.828 MPa) than those impregnated with E. suaveolens extract (2.751 MPa) and CCA (1.452 MPa). Thus, when chemical treatment is the only option to increase the service-lives of laminates against bio-deterioration, inorganic preservatives (e.g., CCA) should be the less favourable choice due to their weaker bonding strengths than extracts from organic sources.