Lignocellulosic biomass is a sustainable alternative to the petroleum-derived chemical for the development of biobased wood adhesive, which motivates the integrated biorefineries to effectively convert biomass feedstock into desirable chemicals. Herein, lignin recovered from kraft biorefinery (L-KB) and two bio-oils, BO-SL/L and BO-FP/PW, prepared from laboratory scale solvent liquefaction of lignin and fast pyrolysis of pinewood, respectively, have been used to substitute 50% (w/w) of phenol in phenol-formaldehyde (PF) resin system. To this end, we first studied the molecular structural characteristics of moieties derived from lignin and polysaccharides present in L-KB, BO-SL/L, and BO-FP/PW via FTIR, 13C-1H HSQC 2D-NMR, and GCMS techniques. Further, the obtained resin adhesive structures were examined by FTIR and 1H-NMR spectroscopy, which confirms methylene bridges appearance during the resin preparation. Subsequently, to understand the curing behavior of each of the resin with hexamethylenetetramine (HMTA) curing agent, DSC analysis was performed, which helps to optimize the bonding process. The resulting bonding strength of each of the resin adhesive, measured by gluing two pieces of wood, reported significantly different adhesion ability due to structural differences, which was analyzed by two-way ANOVA followed by Tukey's post hoc test. Overall, this study represents a comparative strategy for substituting biorefineries derived phenolic part in the PF resin system to conventional petroleum-derived phenol without compensating adhesion ability when applied to the wood. This provides an effective solution to produce biorefinery-derived PF for adhesives applications.

Synthesis of biobased phenol-formaldehyde wood adhesives from biorefinery derived lignocellulosic biomass

ACS Fall 2021

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