An alternative to phenol, a petroleum-based nonrenewable resource, in phenol-formaldebyde resins must be developed to support the wood-based panel industry. Tannins are the best substitute for phenol in this case. Tannin from black wattle (Acacia mearnsii) can be liquified with phenol in the presence of an acid catalyst. In this study, tannin replaced 33 percent of the phenol in the preparation of resol-type plywood adhesives. Loblolly pine (Pinus taeda) plywood bonded with the liquified tannin resin had strengths and wood failures that were comparable to commercial phenol-formaldehyde adhesives and significantly better than unmodified tannin-formaldehyde adhesives when used to bond Southern Pine under bonding conditions commonly employed with phenol-formaldehyde resins
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Santana et al. (1995) studied this question.