• Mcintosh, Charles
• Grigsby, Warren
• Warnes, Jeremy

Abstract

Many have recognised the potential of tannins such as those extracted from bark,to substitute more expensive petrochemical components in adhesives for wood gluing applications. Reported is an investigation on the dissolution and reactivity of pine bark tannin in adhesive bond strength development,describing attempts to overcome the low cross-link density and vitrification usually associated with such adhesive systems. Use of tannin/phenol resorcinol formaldehyde adhesives determined a preference for spray dried pine bark extracts over the concentration of the aqueous extract. Spray dried tannin needed to be adequately mixed and dissolved prior to blending with PRF resin to achieve good adhesive bond strength. Adjustment of water and sulfite tannin solution pH increased solubility and led to substantially greater adhesive performance. Incremental increases in tannin pH led to greater adhesive strength and wood failure with an optimum tannin solution pH of ca. pH 9,which was a balance between tannin/PRF glue mix properties including viscosity,reactivity and adhesive strength.

Topics

• density
• impedance spectroscopy
• strength
• viscosity
• activation
• wood
• resin