Utilização da madeira de seringueira para produção de madeira laminada colada

Abstract

The aim of this study was to evaluate the properties of rubber wood (Hevea brasiliensis) treated with preservatives based on chromated copper borate (CCB) and pyrethroid (Pentox) for production structural pieces of glued laminated timber. Six trees with age close to 12 years and diameter at breast height (DBH) higher than 25 cm were obtained. The chemical composition of the wood was analyzed (extractives, insoluble lignin, ashes and holocellulose) and after the treatments, observations were made on the anatomical structure, and the determination of pH, modulus of elasticity (MOE), modulus of rupture (MOR), parallel compression strength, shear strength, hygroscopic equilibrium moisture, apparent density and shrinkage. The preservative treatment with CCB was performed by sap-displacement method, while Pentox treatment was performed by brushing. The beams of glued laminated timber were produced with 3 veneers with dimensions 6.0 x 2.0 x 120.0 cm by beam, in a total of 5 pieces per treatment. For comparison purposes, samples were also produced with untreated rubber wood. Two different adhesives (vegetal polyurethane and resorcinol formaldehyde) were evaluated. The properties of MOE, MOR and shear strength of the glued laminated timber samples were determined. The rubber wood showed extractives content of 9.97% and insoluble lignin of 25.84%. The treatment with CCB caused a significant increase in the pH of the wood. In addition, the rubber wood showed an anisotropy index higher than 1.5. For the properties of MOE and shear strength, values of 6863.75, 6471.97, 6494.50 MPa and 10.89, 12.54, 9.41 MPa were obtained for the rubber wood untreated, with CCB and Pentox, respectively. The values of MOR and shear strength for the glued laminated timber beams treated with Pentox and untreated did not show statistical differences for both types of adhesives. For MOE, there was no statistical difference between the preservative treatments. In general, treatment with Pentox did not impair the properties of glued laminated timber, while the treatment with CCB resulted in loss of mechanical strength.