Propriedades químicas de extratos tânicos da casca de Pinus oocarpa e avaliação de seu emprego como adesivo

Abstract

This work evaluated the properties of aqueous extracts obtained from the bark of Pinus oocarpa under addition of sodium sulfite and sodium bisulfite and the possibility of employment of tannins from the bark as an adhesive for bonding wood. After evaluation of the chemical properties of tannic extracts it was decided to employ the extraction with distilled water under addition of / 5% sodium sulfite to prepare for the tannin-formaldehyde adhesive. Adhesive phenol formaldehyde and urea-formaldehyde were modified with 10% tannin Pinus oocarpa and the effect of this addition on the quality of the adhesive was evaluated. The addition from the bark of Pinus oocarpa showed that it is possible to use pure tannin as an adhesive because of its good gluing characteristics. The addition of tannic extract to synthetic adhesives contributed to increase viscosity values. Thus the substitution of synthetic adhesives by tannins is possible only up to 10%.