A new project supported by the German ministry of food and agriculture and agency for renewable resources has recently kicked off aimed at the development of bio-based reinforcing layers for solid wood construction materials to replace with petrochemical products currently used.
The project is a collaboration between Leverkusen, Germany-based speciality chemical company Covestro and four partners: Sortimo International GmbH, the German Institutes of Textile and Fiber Research Denkendorf (DITF), the Institut für Kunststofftechnik (Institute for Plastics Engineering, IKT) at the University of Stuttgart and the Fraunhofer Institute for Chemical Technology (ICT).
The layers will be based on a polyurethane system, which will be reinforced with cellulose fibres and more than 90% bio-based, contain no additives and exhibit “excellent flame retardance and weathering resistance”, said Covestro.
The project has been launched in response to the increasing use of solid timber construction techniques in urban spaces.
The main materials used to manufacture the construction materials are cross-laminated timber and glued laminated timber.
Both materials, according to Covestro, consist of alternate layers of wood and thinly spread polyurethane resin, and can be further reinforced by aramid, glass or carbon fibres.
Over the course of this project, the researchers will seek to find bio-based alternatives to the fossil-based resins and fibres that have been used to date.
According to Covestro, the company is pursuing “a combination of biogenous, aliphatic polyisocyanates and polyols based on vegetable oils.”
“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,” explained Dr Paul Heinz of Covestro, who is coordinating the research project.
In terms of manufacturing, project partners have opted for pultrusion, a continuous industrial production process for highly filled, continuous 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.
Sortimo will produce an industry-standard model component that 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 due to forest restructuring.