Lignin-modified phenolic resin: synthesis optimization, adhesive strength,and thermal stability

Lignin-modified phenolic resin has been prepared by replacing phenol with l ignin at different weight percentages. The resin synthesis was optimized by varying the molar ratio of phenol to formaldehyde, the concentration of so dium hydroxide, and the reaction time by measuring parameters such as the g elation time, flow time, solids content, pH, and specific gravity. The ther mal stability of lignin-modified phenolic resin was studied by DSC, TGA, an d isothermal analysis, and it was found that lignin-modified phenolic resin is thermally more stable than pure phenolic resin. The adhesive strength o f lignin-modified phenolic resin was determined by the lap-shear method, wh ich showed that the lignin-modified resin retains 78% of the adhesive stren gth for wood-wood systems and 86% of the adhesive strength for Al-Al system s.