Research progress in the lignin-based formaldehyde-free wood adhesives

DI Mingwei;WANG Sen;YAO Ziwei;Materials Science and Engineering College,Northeast Forestry University;

formaldehyde-free;;lignin;;soybean protein;;activation;;wood adhesive

Lignin as a by-product of the pulping process is also a renewable product abundant in nature. It has great potential for many applications in various industries, including not only traditional products, e. g., resins and composites,but also emerging materials,e. g.,biofuel and commodity chemicals. Wood adhesives are mainly prepared from petroleum-based polymers nowadays. However,with the depletion of petroleum resources,environmental damage and increasing concern for the toxic volatile substances from adhesives,it is necessary to find renew-able alternatives to prepare formaldehyde-free wood adhesives. As a low-cost and abundant biomass resource,lignin was used to prepare wood adhesives,which attracted the attention of people. The recent research progress of the lignin-based formaldehyde-free wood adhesives were reviewed in this paper,such as lignin-furfural adhesive,lignin-polyurethane adhesives,lignin-tannin adhesive,lignin-polyethyleneimine adhesive,laccase-activated lignin adhesive and lignin-soybean protein adhesive. The relevant information on several lignin adhesives and their applications in the wood-based panel industry was introduced. This reviewwas focused on the chemical modification of lignin structure( such as phenolization,hydroxylation and laccase activation) and preparation of adhesives from lignin and various bio-resources. Meanwhile,the main reaction mechanism and performance parameters about wood-based panel were listed to indicate the property difference of lignin adhesives,including mechanical properties and water resistance.Some problems and solutions about lignin-based wood adhesives were analyzed,and the prospect of lignin-based wood adhesives was discussed. Although compared with traditional urea-formaldehyde resin and phenolic resin,mechanical properties and water resistance of lignin-based wood adhesive were still needed to be improved,it showed great potential in the wood-based panel industry with the development of relevant research.