WOOD ADHESIVES BASED ON TANNIN EXTRACTS FROM BARKS OF SOME PINE AND SPRUCE SPECIES

Barks available in commercial quantities in Australia and overseas have been examined for their efficacy as raw materials for conversion to high quality adhesives for reconstituted wood products. Previously bark from mature Pinus radiata was found to be suitable. This paper examines the suitability of barks from four mature pine species (Pinus caribaea, Pinus elliottii, Pinus pinaster and Pinus sylvestris), one young pine species (Pinus radiata) and one spruce species (Picea abies). Only the bark extracts of Pinus caribaea and Pinus pinaster gave high quality (Type A bond, WBP) wood adhesives. The gluing properties of the adhesives derived from the extracts appeared to be dependent on their contents of formaldehyde-reactive polyflavanoids as indicated by their Stiasny values, with a value of 65% being the minimum for producing a high quality adhesive by the methods used.