Effect of point of preservative addition on the mechanical and physical properties of strandboard treated with Tanalith 3485

IRG/WP 00-40152

G J Goroyias, M D C Hale

Preservative has been added to a PF bonded strandboard at various different stages in the manufacturing cycle and the physical and mechanical properties of the boards have been evaluated (modulus of elasticity, modulus of rupture, thickness swelling, water absorption, internal bond strength, and shear strength). Preservative addition has been examined at five different stages namely green strand diffusion, strand vacuum treatment, glue-line addition, heat and cold quench and by post manufacture vacuum treatment. The treatment methods had marked effects on the mechanical properties of the boards. The post manufacture vacuum treatment at 3% resin content boards showed poor IB strength after wetting but a higher resin content improved the IB strength but did not reduce thickness swelling significantly. Glue-line treatment was done by spraying wood strands with preservative prior to resin blending and this produced boards with inferior physical properties to the other application methods fully evaluated. Higher pressing temperatures alleviated this. Vacuum pressure impregnation and diffusion treatments of the strands prior to pressing produced boards with similar properties to the control boards, produced without preservative addition. A heat and cold quench treatment was used to simulate the immediate treatment of hot boards by dipping after release from the hot press in a production line. This treatment gave properties slightly inferior to the control boards and a poor preservative distribution. The preservative distribution in the vacuum treated strands strandboard and the diffusion treated strands strandboard was uniform.


Conference: 00-05-14/19 Kona, Hawaii, USA

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