Eco-friendly production technologies for poly(vinyl acetate) wood adhesives: Recent progress and challenges - A short review

Wood adhesives have come a long way from urea-formaldehyde (UF) resins to waterborne poly(vinyl acetate) (PVAc) latex polymerized by emulsion polymerization. Nevertheless, while modern adhesives are more environmentally friendly, they still contain low concentrations of substances considered to be toxic or carcinogenic. Increasing social awareness about the environmental friendliness and toxicity of chemical compounds has pressured producers of wood-based materials and furniture to develop new green technologies and eliminate potentially dangerous chemical compounds. The crucial parameter for wood adhesives is the durability class of water resistance according to the EN204:2016 standard. To achieve a higher class, i.e., D3 or D4, it is necessary to use a crosslinked polymer. Crosslinking is usually performed using N-(hydroxymethyl)acrylamide monomer (NMA), UF resins, or glutaraldehyde. NMA contains and emits formaldehyde, which is poisonous and carcinogenic, so the chemical industry is trying to replace this substance with greener, formaldehyde-free, and eco-friendly substitutes, such as silanes, bio vinyl and acrylate monomers, or 2,5-diformylfuran. In this short review, we focus on demonstrating updated green approaches to developing wood adhesives and methods to eliminate the presence of unwanted substances such as formaldehyde. We present the technologies for producing PVAc step by step and the stages that need to be further investigated or improved.