Improving the weather resistance of glue-laminated jarrah and karri

IRG/WP 94-40017

J Balfas, P D Evans

Surface modification and dimensional stabilisation significantly increased the dry and wet shear strength of karri and jarrah lap-shear specimens (laminates) bonded with resorcinol formaldehyde. The combination of surface modification (sanding/sodium hydroxide treatment), and furfurylation produced the highest dry and wet shear strengths. Acetylated laminates had the lowest dry bond strength, but the lowest loss of strength on wetting. In most cases karri laminates showed higher dry, but lower wet shear strength than jarrah. Untreated laminates rapidly delaminated during artificial accelerated weathering, but surface modification and dimensional stabilisation significantly increased the resistance of specimens to delamination. Only a small proportion (5-10%) of acetylated specimens delaminated during accelerated weathering and surface modified acetylated laminates showed no delamination during the weathering test. Laminates treated with a combination of surface modification and furfurylation showed less delamination than specimens treated by surface modification alone. Treatments that increase both glue bond strength and dimensional stability appear to offer an effective means of improving the weathering resistance of glue-laminated karri and jarrah.


Keywords: WEATHERING; GLUE-LAMINATED TIMBER; CHEMICAL MODIFICATION; SANDING; SURFACE ACTIVATION; ACETYLATION; FURFURYLATION; RESORCINOL FORMALDEHYDE; JARRAH; KARRI

Conference: 94-05-29...06-03, Nusa Dua, Bali, Indonesia


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