EFEITO DO TRATAMENTO TÉRMICO SOBRE A RESISTÊNCIA AO CISALHAMENTO DA LINHA DE COLA EM PAINÉIS OSB

Research to improve dimensional stability of oriented strand boards (OSB) through thermal treatment has been done. It aims to reduce the higroscopicity of the wood particles as well as to relieve the compression stresses generated during pressing process. In spite of the advantages, the thermal treatment above 160oC can inactive the surface of the wood, reducing the penetration of the adhesive and, this way, reducing the quality of the adhesion. The sanding of the surface of OSB panels can remove this effect, increasing the quality of the adhesion and the glue line strength. The present study aimed to evaluate the effect of the thermal treatment on the glue-line shear strength of OSB panels and the effect of the sanding process on this strength, as well. Commercial OSB were thermally treated according to two temperature levels (190 and 220oC), three times (12, 16 and 20 minutes). Eighty-four samples were cut, both of them were sanded before the gluing (resorcinol-formaldehyde, 360 g/m²). The glue-line shear strength testing was conducted according to ASTM D 1037 standard. The results reveled that the proposed thermal treatment reduced slightly the shear strength The interaction factor between temperature and time on these results was identified. However, sanding process removed this effect and improved significantly shear strength. Therefore, the thermical treatment imparted little effect on the glue-line shear strength, while the sanding process improved the quality of the adhesion in OSB panels.