ASSESSMENT OF THE TECHNICAL FEASIBILITY OF PRODUCING EDGE-GLUED PANELS WITH WOOD FROM THREE BRAZILIAN DRY FOREST TREE SPECIES
Edge-glued panels; Brazilian dry forest wood species; polyvinyl acetate; castor oil polyurethane; polymer isocyanate emulsion; melamine-urea formaldehyde
This article reports an experiment to evaluate the technical viability of producing edge-glued panels (EGPs) with wood from three Brazilian dry forest species: Aspidosperma pyrifolium, Cordia oncocalyx and Mimosa caesalpinifolia. Five adhesives were used: polyvinyl acetate D3 (PVA D3), polyvinyl acetate D4 (PVA D4), castor oil polyurethane (CP), polymer isocyanate emulsion (PIE) and melamine-urea-formaldehyde (MUF). The experimental design was completely randomized, involving 3 wood species, 5 adhesives and 5 replicates, totaling 75 observations. Physical-chemical properties of the wood species, basic density, extractives content and pH, were determined. Wood joists were laterally bonded and after conditioning were sawn to obtain the test specimens. Before evaluation of bonding quality by mechanical testing, the specimens were separated into groups, each one submitted to a different pretreatment: dry and moist condition and after 6-hour boil test and boil cycle test. The glueline performance indicators were the 5th lower percentile and the percentage of wood failure. The three wood species showed potential for production of EGPs and at least two adhesives (CP and MUF) resulted in bonded joists able to withstand the 6-hour boil test and the boil cycle test. Despite the observation of a negative correlation between extractives content and 5th lower percentile, when the adhesive MUF was used, this detrimental effect was overcome and all the joists reached the minimum strength required by the technical standards.