Microwave‐assisted hydrothermal liquefaction of lignin for the preparation of phenolic formaldehyde adhesive

Abstract

ABSTRACT This study aimed to produce phenolic formaldehyde (PF) adhesives using the liquefaction product of bagasse lignin (LPBL) as a partial substitute for petroleum‐based phenol. Lignin was extracted from bagasse using 93% acetic acid solution and was rapidly degraded in hot‐compressed water by microwave heating using oxalic acid as catalyst. The liquefaction yield reached 78.69% under the optimal reaction condition. Gas chromatography–mass spectrometry (GC/MS) analysis showed that the main chemical compounds of the liquefaction product included mono‐substituted and bis‐substituted phenols, such as 2,6‐dimethoxyphenol, 4‐hydroxybenzaldehyde, and so on. The LPBL was employed to replace a portion of phenol at varying ratios from 0 to 20 wt % in the preparation of PF adhesives. The molecular weight, viscosity, and adhesive strength of LPBL‐PF adhesives were found to be lower than those of pure PF adhesives. With the phenol replaced by LPBL up to 20%, the viscosity and adhesive strength of the resin were 4.046 Pa s and 1.017 MPa, respectively. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44510.