The influence of preservative treatment on laminated P. patula bond performance

Abstract

In this research, the effect of wood preservatives and wood properties on one-component polyurethane bond performance in Pinus patula laminates was investigated through shear and delamination tests. Concentration levels of 2 and 4% of chromated copper arsenate (CCA), and 1.67 and 3.30% of disodium octaborate tetrahydrate (DOT) were used. Different levels of wood density and wood type (viz. sapwood only and samples with more than 35% heartwood), was considered. Based on the ASTM D905, SANS 10183-4-2, and EN 14080 standards, the shear strength, wood failure and delamination results suggested that engineered wood products can be produced from CCA and DOT treated Pinus patula that was laminated using polyurethane adhesive. All 20 groups in the experiment met the standard's requirements for shear strength, wood failure percentage and total delamination. It was interesting to note that the specimens treated with the highest concentration of preservative (4% CCA) displayed superior shear strength in comparison to the 2% CCA treated samples and the untreated control group. However, the increased levels of preservative also had a negative effect since it resulted in a decreased wood failure percentage. Overall, the DOT-treated specimens displayed more consistent performance in comparison to CCA specimens, in terms of shear strength and wood failure. The results also indicated that wood properties play a significant role in the strength of bonds. As expected, high-density samples produced higher shear strength in most cases. The DOT treated samples were found to have a higher resistance to delamination in comparison to CCA treated samples. Finally, the preservative treatment concentration levels should be carefully selected, as the study found that with increasing the preservative concentration, delamination increased.