Covestro is participating in a project to develop bio-based resin reinforcing layers for solid wood construction materials to replace the petrochemical products used to date.
The polyurethane system, reinforced with cellulose fibres, will be more than 90% bio-based, contain zero additives and exhibit excellent flame retardance and weathering resistance. The project is being supported by the German Federal Ministry of Food and Agriculture (BMEL) through the project sponsor Fachagentur Nachwachsende Rohstoffe (Agency for Renewable Resources).
Solid timber construction techniques employ materials such as cross-laminated timber and glued-laminated timber. Both consist of alternate layers of wood and thinly spread polyurethane resin. Aramid, glass or carbon fibres embedded into the layers of resin further enhance the stability of the construction elements.
Over the course of the recently launched project, the researchers want to find bio-based alternatives to the resins and fibres used to date. They are pursuing a combination of biogenous, aliphatic polyisocyanates and polyols based on vegetable oils. The resulting polyurethanes should exhibit low flammability and good weathering resistance, so that no special additives are needed to enhance either property.
When it comes to reinforcement, the scientists favour cellulose fibres such as those extracted from regenerated cellulose.
“At the end of this process, we will have the first ever reinforcing materials for use in timber construction that are made up of at least 90% renewable raw materials,” says Dr. Paul Heinz from Covestro, who is coordinating the research project.
This, he claims, will make state-of-the-art timber construction with cross-laminated and glued-laminated timber even more sustainable.
To manufacture the construction elements, the project partners have opted for pultrusion, a continuous industrial production process for fibre reinforced composite profiles. Pilot facilities run by the Fraunhofer Institute are being used to manufacture flat profiles for testing and optimising the necessary tools and process parameters.
During the project, Sortimo will produce an industry-standard model component that will be used to evaluate the technical, economic and ecological potential of the new material and production process for the construction industry. Beech wood is being used for the component, as this material is becoming available in growing volumes due to forest restructuring.
To reduce its dependency on fossil raw materials, Covestro is looking to manufacture a growing number of products and their associated precursors from renewable raw materials.