Bio-based resin in the works for CLT, glulam

Working with four partners, Covestro is developing bio-based layers for wood construction materials to replace the petrochemical products used till now. The polyurethane system, which is reinforced with cellulose fibers, exhibits good flame retardant properties.

The main materials used to manufacture construction elements are cross-laminated timber and glued-laminated timber. Both materials consist of alternate layers of wood and thinly spread polyurethane resin.

If aramid, glass or carbon fibres are embedded into the layers of resin, they create reinforcing segments that further enhance the stability of the construction elements.

Over the course of the project, the researchers has focussed on finding bio-based alternatives to the fossil-based resins and fibres and are looking at a combination of biogenous, aliphatic poly-isocyanates and polyols based on vegetable oils.

The resultant polyurethanes were required to 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 fibers such as those extracted from regenerated cellulose. Researchers are confident that they will have the first ever reinforcing materials for use in timber constructions that are made up of at least 90% renewable raw materials.

An industry-standard model component will then 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 because of forest restructuring.

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