ABSTRACT
Tannins of eucalyptus bark were obtained by extracting with water under addition of 8% Na2CO3 and 4% Na2SO4. To determine the adhesive properties was evaluated the viscosity, density, solids, gel time, and pH of adhesive of black wattle 50%, urea 100%, tannin extracted from the eucalyptus bark with Na2CO3 30% and Na2SO4 50%, and urea with tannin extracted from the eucalyptus bark of ratio of 90:10 and 80:20. Waste eucalypts wood (density classified into three classes: low, medium and high) were glued to the hot tannic and synthetic adhesives. The resistance was determined by the glued joints shear strength and wood failure. It can be concluded that the adhesive compounds by tannin extracted with sodium sulphate and pure sodium carbonate (100%) had desirable characteristics for the production of tannins, but not enough for its use as adhesive wood in its entirety and it may be used in the urea-formaldehyde glue gem enrichment in the timber. The higher shear strength on wood occurred in the high density class for all adhesives used, while larger gaps in wood adhesives in most tests it occurred in the wooden low densities.
Keywords
Waste timber; eucalypt; natural adhesives; tannins; hot glue