Adesivos à base de taninos das cascas de duas espécies de eucalipto para produção de chapas de flocos

Eucalyptus grandis and Eucalyptus pellita bark tannins were extracted with hot water, with addition of 4,5% of sodium sulfite, for a three hours period, at temperatures of 70oC and 100oC, respectively. The tannins were reacted with acetic acid and sodium sulfite, for reduction of adhesive viscosity. Calorimetric exploratory differential techniques were used to determine adhesive kinetic parameters. Flakeboards were fabricated with Pinus elliottii wood flakes, using 8% or 10% of Eucalyptus grandis or Eucalyptus pellita tannin- based adhesives or 8 % of commercial urea-formaldehyde adhesive. Board properties were determined according to ASTM D-1037 standard. Except for moisture related properties, the boards fabricated only with tannin- based adhesive were superior to the minimally acceptable ANSI/A 208.1-93 standard. The flakeboards fabricated with Eucalyptus grandis bark tannins were better than those fabricated with Eucalyptus pellita bark tannins.