Wood adhesives of today perform very well in terms of bonding performance and moreover they are also inexpensive. However, most wood adhesives are derived from petroleum-based chemicals, which is a limited and non-renewable resource. Furthermore, some of these chemicals, for example formaldehyde, also have a negative impact on the environment and on human health. With the increasing concern for the environment, it is necessary to find alternatives derived from bio-based resources that can replace petroleum-based polymers. To enable this transition it is important that the adhesive properties in terms of bond strength, water resistance and heat resistance are similar, and that the alternative can compete in terms of cost. It has proved difficult to find bio-based alternatives that fulfill all requirements; they are often too expensive or have poor water resistance. Proteins, for example, have shown very good results and a lot of research is today focusing on protein-based wood adhesives.[1] However, protein is also a valuable food source, and therefore not an ideal candidate for the production of adhesives. Motivated by the wood-biorefinery concept of using side-streams from the forest-products industry, and by the surprisingly good results from our previous studies on other polysaccharides in this type of applications,[2] we are now investigating the possibility for using hemicelluloses from wood as binders in wood adhesives. Water dispersions of xylan were prepared and evaluated. However, xylan itself cannot be used as a wood adhesive due to its limited bonding performance, especially regarding the water resistance. Therefore, the addition of dispersing agents, poly(vinyl alcohol) or poly(vinyl amine), and crosslinkers, such as glyoxal or hexa(methoxymethyl) melamine, were evaluated. Several of the xylan dispersions demonstrate good bond strength and surprisingly good water and heat resistance when gluing wood veneers; especially xylan together with a relatively small amount of poly(vinyl amine) shows remarkable water resistance and bond strength.[3]<br/>[1] Nordqvist et al. Int. J. Adhes. Adhes. (2010) 30, 72-79<br/>[2] Norström et al Ind. Crops Prod.(2014) 52, 736-744<br/>[3] Norström et al Eur.Pol. J. 2015, 67, 483–493

Polysaccharides as green binders for wood adhesives

251st National Meeting (2016)

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