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KeywordsBrown-rotted lignin (BRL) Brown-rot fungi Brown-rotted Douglas-fir wood Phenolic hydroxyl group . Formaldehyde reactivity Phenol-formaldehyde resin Flakeboard Southern pine SummaryData on an adhesive System for flakeboard is presented in which 35% of the phcnol in a phenol-formaldehyde (PF) resin is replaced with brown-rotted lignin (BRL). This BRL, which has previously been shown to be rieh in phenolic hydroxyl groups, has a higher formaldehyde reactivity than a purified Kraft lignin. Formulation characteristics and molecular weight of the BRL-PFresin were determined and compared with a control PF resin. The physical properties of flakeboard including intcrnal bond (IB), dry static bending (modulus of rupture, MOR), accelerated agingMOR, water absorption and thickncss swelling were examined and found to be comparabie for both adhesivcs.The results of this study demonstratc that BRL can be used äs a partial substitute for phenol in structural wood adhesives.

Organosolv wheat straw lignin extracted using the CIMV process TM is a linear, low molecular weight, and natural phenolic oligomer. In this study, organosolv wheat straw lignin was tested as a substitute for 50% to 70% of the phenol in a phenol-formaldehyde-resol resin. The lignin was used without any chemical modification in a one-step synthesis reaction. Parameters such as reaction time and formaldehyde-to-phenol sources (phenol + lignin) mass ratios were optimized to achieve the requirements for industrial wood adhesives in terms of pH, viscosity, and dry matter. For the first time, the formaldehyde ratio was studied in order to reduce resin residual free formaldehyde below 1%. Lignin-phenol-formaldehyde resins were successfully synthesized up to a phenol substitution rate of 70% and showed physico-chemical properties close to standard phenol-formaldehyde resins. The thermo-mechanical properties analyzed in dynamic load thermo mechanical analysis were similar to those of the reference resins. Plywood panels manufactured using these lignin-based resins reached the specifications for industrial panels according to the French standard for exterior plywood panels. Moreover, the formaldehyde content of these plywoods was low enough to satisfy even the most rigorous legislation.

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