Gum dispersions as environmentally friendly wood adhesives

• Gums can be used as binders for wood adhesives.
• Locust bean gum dispersion fulfill the criteria for a D2 and WATT 91 wood adhesive.
• Locust bean gum dispersions can be pressed at room temperature as well as at elevated temperatures.

Today, wood adhesives are mainly prepared from petroleum-based polymers. There is an ambition to decrease the utilization of petroleum-based raw materials and introduce bio-based polymers instead. However, the utilization of bio-based polymers is often limited due to insufficient properties in terms of water resistance or heat resistance. In this study bio-based dispersions have been prepared of locust bean gum, guar gum, xanthan gum and tamarind gum and evaluated as wood adhesives. Due to the high viscosity of the dispersions, a low dry solids content of 6 wt% was used. The film forming properties have been investigated and contact-angle measurement have been performed to obtain an indication of water resistance. Wood substrates have been bonded together and the bonding performance has been evaluated with different techniques. The gum dispersions have been compared with a commercial poly(vinyl acetate)-based wood adhesive and the results demonstrate that gums can be used as binders for wood adhesives. Locust bean gum dispersions show remarkable results – comparable to the commercial wood adhesive – even though the dry solids content is very low. The locust bean gum dispersion fulfills the D2 and WATT 91 requirements for wood adhesives according to the European Standard EN 204 and European Standard EN 14257.