University of Stuttgart – biopolymers as construction material of the future?
The Institute of Building Structures and Structural Design (ITKE) at the University of Stuttgart is investigating whether it is possible to replace traditional plastics in the building industry with natural fibre-reinforced biopolymers. As part of the project, which is being funded by the Deutsche Bundesstiftung Umwelt, the ITKE researchers are working with the Nimbus Group to develop transparent lightweight building boards from biopolymers with acoustic function.
The fact that fibre-reinforced polymers can be used for many applications demonstrates the enormous flexibility of the material. Fibreglass-reinforced polymers have also started to be used in the building industry. The Institute of Building Structures and Structural Design (ITKE) at the University of Stuttgart, directed by Prof. Dr.-Ing. Jan Knippers, focuses mainly on fibre-reinforced polymers, bionics and the development of new building materials.
The huge resistance to acids and bases and their excellent corrosion resistance makes fibreglass-reinforced plastics an excellent construction material. In terms of design, the fibreglass-reinforced polymers are also very flexible in terms of shape and have excellent transparency characteristics. In 2008, the ITKE erected the first steel fibreglass-reinforced polymer bridge in Friedberg (Hesse). Prof. Knippers and his team took advantage of the light weight of fibre-reinforced polymers to prefabricate most of the bridge and transport it in one piece to the construction site. One of the goals of the construction of the new bridge is to reduce maintenance costs through improved weathering and corrosion resistance. Fibre-optic sensors integrated into the plastic material enable the ITKE engineers to monitor the bridge over many years in order to compile scientific documentation of the behaviour of the plastic.
As part of her doctoral thesis, the architect Carmen Köhler is investigating the applicability of natural fibre-reinforced biopolymers in the construction industry. In contrast to fibreglass-reinforced polymers, natural fibre-reinforced polymers are considerably lighter, emission stable and breathable. "Construction material that is breathable at the same time as preventing moisture from penetrating, is also of major interest in architectural terms," said Carmen Köhler explaining that she finds the material suitable for facades and insulations.
In a project funded by the Deutsche Bundesstiftung Umwelt (German Federal Environmental Foundation), the scientist is focusing on the development of transparent building components from biopolymers with a proportion of renewable materials that is as high as possible. Working with the Nimbus Group, the ITKE is developing a transparent lightweight building board from biopolymers with acoustic function.
"We are currently testing a broad range of materials for their suitability in the production of building boards," said Carmen Köhler explaining that the group of researchers is investigating polylactide, cellulose acetate and other materials. Selection criteria are price, temperature stability and the potential use of additives during processing. "We hope that the material will be classified as B2 or even B1 class construction material," said Köhler explaining that B1 and B2 refer to the degree of inflammability of materials, which should be as low as possible.
Köhler envisages that the lightweight building boards will be used in open-plan offices to separate individual work stations. The researchers have high requirements in terms of design. The acoustic function of the boards also has an important role to play. "Microperforation decelerates the sound waves at the plates, which leads to damping room acoustics." Renewable materials are thus used to create an acoustic room separation in which the optic permeability of the room is maintained.
Biopolymers are also suitable for outdoor use. The testing of the material has shown that cellulose acetate and polylactide are very resistant to UV. The biopolymers did not become discoloured to the same extent as traditional transparent polymers when exposed to sunlight.
Cellulose acetate is already used for transparent heat insulation. “For outdoors, a number of quite interesting applications can be imagined, all of which have completely different requirements on the temperature,” said Köhler. The goal of Köhler’s research is to find out whether transparent biopolymers can be used to replace traditional transparent polymers in the building and construction industry.