ThermoBiK: Climate protection through bio-based adhesives

The development of new bio-based adhesive and adhesives based on polyurethane dispersions (PUD) was the focus of the project “Thermoaktivierbare Bio-Klebstoffe“ (“Thermoactivated bioadhesives“) – ThermoBiK for short. The aim was to create adhesive formulations with a bio-based carbon content of more than 50 percent and at the same time with a 25% lower carbon footprint compared to conventional thermoactivated adhesives. To assess these two parameters, Fraunhofer UMSICHT carried out a life cycle assessment for two applications developed by our industrial partners: sole bonding in shoe production and the lamination of 3D furniture fronts with decorative film. Processes ranging from the extraction of resources to the production of PUD and the disposal of adhesives were investigated.

In order to make products more environmentally friendly, alternatives to fossil raw materials are increasingly in demand in industry. The demand for high-performance adhesives based on renewable raw materials is thus growing in shoe and furniture production. Greenhouse gas reductions and an increased proportion of bio-based substances in PUD can be achieved by producing crystallizing polyester polyols from bio-based dicarboxylic acids and diols for use in PUD adhesives. As part of the ‘Thermoactivated bioadhesives’ project, various such adhesive systems were formulated and tested for applications on wood and footwear.

The material developments by the industrial partner Covestro show that semicrystalline polyester components can be produced from bio-based raw materials and used to synthesize stable PUD with a solids content between 40 and 50 percent. It is technically possible to use bio-based PUD in existing adhesive applications and in their joining and processing steps. In addition, tests at Jowat SE have shown that synthesized bio-based PUD is suitable for the lamination of 3D furniture fronts with decorative film and can replace conventional PUD in this area.

In addition to their good adhesive properties, bio-based PUD also offer advantages in terms of climate protection. According to the life cycle assessment carried out by Fraunhofer UMSICHT, bio-based PUD allow greenhouse gas emissions to be reduced by more than 25 percent in comparison to  conventional crude oil-based PUD Their bio-based carbon content of the developed PUD is well over 50 percent.

• Covestro Deutschland AG
• Jowat SE
• Henkel AG & Co. KGaA