A Review on Lignin‐Based Phenolic Resin Adhesive

Abstract

Replacing petroleum-based chemicals with biomass-based alternatives is becoming more and more important for the development of a low-carbon economy around the world. The latest life cycle assessment displayed that partially replacing phenol with biobased lignin in the process of synthesizing phenolic resin adhesives used in wood panels industry can remarkably reduce carbon emissions and negative environmental impact. The macromolecular structure of lignin is similar to that of phenolic resin and the basic structure unit is similar to that of the phenol, thus endowing it with the potential to substitute phenol and reduce the release of formaldehyde in the preparation process of phenolic resin. Importantly, the lignin-based adhesive exhibits improved performance and reduced cost compared with the petroleum-based adhesive due to the reduced adding amount of petroleum-based volatile components. However, the intrinsic large steric hindrance, structural heterogeneity, and low activity of the natural lignin limit its further application in the adhesive. Many researchers have developed the activation methods such as physical modification, chemical modification, and biological modification to overcome these issues. The different modification of the lignin and their application in the adhesive area are mainly summarized here. Besides, the modification methods and the curing mechanism are also discussed.

Hydrogen-Bonding Interaction-Driven Catechin Assembly into Solvent-Free Supramolecular Adhesive with Antidrying and Antifreezing Properties

“…An interesting phenomenon was discovered that there was a negative correlation between the size of phenols and shear strength (Figure S2b) due to the low cross-linking density caused by the steric hindrance. The phenolic hydroxyl groups of CA with a smaller volume were exposed on the molecular surface, while the partial phenolic hydroxyl groups (hydrogen-bond donors) were entrapped inside TA with a larger volume, which limited the efficient cross-linking with ether groups (hydrogen-bond receptors) of PEG 2000 into a stronger adhesive . In contrast, no bulky supramolecular adhesive was observed in the case of CAol/PEG 2000 due to insufficient cross-linking dots in catechol (CAol) .…”

“…The phenolic hydroxyl groups of CA with a smaller volume were exposed on the molecular surface, while the partial phenolic hydroxyl groups (hydrogen-bond donors) were entrapped inside TA with a larger volume, which limited the efficient cross-linking with ether groups (hydrogen-bond receptors) of PEG 2000 into a stronger adhesive. 36 In contrast, no bulky supramolecular adhesive was observed in the case of CAol/PEG 2000 due to insufficient cross-linking dots in catechol (CAol). 37 To scrutinize the effect of the PEG chains with diverse molecular weights on adhesive properties, the different PEG molecules including PEG 400 , PEG 1000 , and PEG 4000 were introduced.…”

Aging Behaviors of Phenol-Formaldehyde Resin Modified by Bio-Oil under Five Aging Conditions

“…Phenol, as the main raw material of PF resin, is derived from petroleum-based chemicals. To reduce the use of phenol, modifiers from renewable natural compounds such as lignin [ 3 , 4 , 5 ], tannin [ 6 ], and cardanol [ 7 ] have been a focus of research in recent years.…”

Modification Mechanism of Phenol-formaldehyde Resin with Crude Bio-oil by Model Compound Method

“…With the promotion of global policies on resource shortage and environmental protection, seeking or developing a renewable resource to substitute phenol for preparing PF is becoming more important. Over the past decade, researchers have successfully produced bio-based PF by replacing phenol with sustainable materials such as lignin [3][4][5][6], tannins [7,8], cardanol [9], furfural [10], glyoxal [11] and bio-oil [12][13][14][15]. Bio-oil, the main product of the rapid pyrolysis of biomass, has been successfully used in the preparation of PF resin in recent years [16][17][18].…”

“…The copyright holder for this preprint this version posted July 6, 2022. ; https://doi.org/10.1101/2022.07.04.498740 doi: bioRxiv preprint past decade, researchers have successfully produced bio-based PF by replacing phenol with sustainable materials such as lignin [3][4][5][6], tannins [7,8], cardanol [9], furfural [10], glyoxal [11] and bio-oil [12][13][14][15]. Bio-oil, the main product of the rapid pyrolysis of biomass, has been successfully used in the preparation of PF resin in recent years [16][17][18].…”