Presently,wood adhesives are mainly derived from petrochemicals; and the two most commonly used adhesives (phenol-formaldehyde and urea-formaldehyde resins) use carcinogenic formaldehyde. This research, inspired by the fact that mussels stick strongly to rocks in water through an adhesive protein, focuses on development of formaldehyde-free wood adhesives fromrenewable resources. The mussel adhesive protein contains unusually high amounts of amino groups, a catechol moiety, and a mercapto group. It was hypothesized that polymers can serve as good wood adhesives as long as they contain sufficient amounts of amino and phenolic hydroxyl groups. To verify this hypothesis, various adhesive systems were investigated: poly (4-vinylphenol) plus polyamines, chitosan plus phenolic compounds, lignin plus polyamines, condensed tannins plus polyamines, demethylated lignin plus polyamines, and chemically modified soy proteins with increased amounts of a mercapto group and a catechol moiety. Results fromthese studies led to the discovery that the residues (mostly lignin) of brownrot fungus-degraded wood could be used to develop a strong, water-resistant, formaldehyde-free wood adhesive. This paper will present the step-by-step efforts in development of adhesives from renewable natural resources using the mussel adhesive protein as a model.
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