Alkaline Copper Quaternary (ACQ) wood preservatives are composed of copper oxide and a quaternary ammonia compound which are extensively used as substitutes for chromate copper arsenate (CCA) in wood preservation. ACQ is less toxic owing to the absence of arsenic or chromium. Preservative treatments change both the physical and chemical properties of wood, consequently affecting the bond integrity of glued products. This study evaluates the influence of ACQ preservative relative to the bonding strength and surface wettability of four tropical hardwoods that are used for making cross laminated timber (CLT). The lumbers were impregnated with 2% ACQ solutions by applying a full cell process treatment. The treated lumbers were evaluated for chemical retention, density increment, wood surface roughness and wettability. Three-layered CLT were fabricated at different parameters i.e., species combination, glue spread rates and clamping pressures, and phenol resorcinol formaldehyde (PRF) as binder. The bonding performance of the CLT was examined through block shear and delamination tests. The ACQ treatment resulted in increased in density, noteably for lower density wood such as batai (15.8%). Higher density wood experienced much less increment: kedondong (0.88%), rubberwood (2.2%) and sesendok (2.4%). Both the chemical retention and cu content followed the same trend. Treated wood of higher density has much rougher surfaces which evidently found to reduce the wettability of wood surface. Generally, ACQ did not significantly affect the bonding properties of CLT produced irrespective of parameters used. Among the wood species, rubberwood shows superior bonding ability either in single or in combination with other species. None of the CLT delaminated after being subjected to vacuum pressure soaking and oven drying.
Professor Dr. Paridah Md. Tahir FASc is currently a Fellow Consultant at the Institute of Tropical Forestry and Forest Products (INTROP), Universiti Putra Malaysia. She has published more than 200 articles in the area of wood/fibre science, polymer composites and pulp & paper. She has co-authored 10 books and more than 100 proceedings, chapters in book, and technical reports. Paridah has secured > RM 12 million research funds and consultancy projects from public, industry and international sources. She had filed 10 patents; three have been granted. Her study on oil palm plywood has been applied in several plywood mills in the country. She is active in developing timber standards for Malaysia and ISO. The department of Standards Malaysia has awarded her with a STAR Award in 2015, a prestigious award given to individuals in recognition of their significant and excellent contribution to standards development in Malaysia. She was recognised as Top Research Scientist Malaysia (TRSM) 2015 and appointed as Fellow of the Academy of Science Malaysia (ASM) in 2018.
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