Technology for Wood and Natural Fiber-Based Materials

Research Project

BioProfile – Extruded and co-extruded profiles from plant residue-reinforced bioplastics for façades, windows and other architectural applications

Window and façade profiles made from plastic are extremely popular due to their durability, low maintenance and good recyclability. In cooperation with the University of Stuttgart, we are developing profiles made from bioplastics in which regionally available plant residues, such as wheat straw, are used as filler material. Thanks to the good formability during the extrusion process, the bio-profiles can be utilized not only for windows and façades but also for diverse architectural applications. With this project, we are contributing towards increasing the proportion of renewable raw materials in the construction industry. .

Schnitt durch ein pflanzenreststoffverstärktes und flammgeschütztes Kunststoffprofil
© Fraunhofer WKI | Manuela Lingnau
Plastic profiles for façades and windows with wheat straw as filler material conserve resources

Whilst the focus of the work at the University of Stuttgart is directed at the implementation of the developed materials in architecture, we at the Fraunhofer WKI are addressing the compounding and profile extrusion as well as the characterization of the bio-profiles. We are conducting research into how the material has to be composed and which additives are needed in order for the profiles to be easily extruded. In addition, we ensure that the bio-profiles fulfill component requirements such as fire protection, UV stability, thermal insulation and durability.

In order to achieve the fire-protection class “flame-retardant”, we pursue the approach of introducing flame retardants into the outer layer of the profiles by means of co-extrusion. We investigate the flame-retardant effect using the UL94 test method, the small-burner test and the cone calorimeter. In order to assess the durability of the flame-retardant profiles, we perform all tests both before and after artificial weathering.

Vier Proben von Weizenstroh in verschiedenen Zerkleinerungsstufen
© Fraunhofer WKI | Richard Deetz
Preparation of wheat straw for compounding

With regard to durability, thermal insulation and UV stability, we test and optimize the physical and mechanical properties of the bio-profiles, thereby encompassing flexural properties, water absorption and swelling, behavior in the hard-body drop test, thermal expansion and thermal conductivity.

The production of the bio-profiles is carried out in accordance with DIN EN 15534-1 for composite materials made from cellulose-containing materials and thermoplastics, usually referred to as wood-polymer composites (WPC) or natural-fiber composites (NFC). As fillers, not only wood fibers and wood-fiber flours are suitable but also, depending on the field of application and regional availability, natural fibers and natural-fiber flours from other vegetable sources, e.g. hemp, flax, sisal, coconut, cotton, kenaf, jute, Manila hemp, banana-leaf fibers, bamboo, rice and wheat straw. For the matrix, various types of petrochemical or vegetable polymers are used, which are obtained from recycled plastics or produced from new raw materials. The Fraunhofer WKI specializes in the development of resource-conserving bio-composite materials. We devise tailor-made solutions for the most diverse areas of application.

Extrusionsanlage mit einer Fassadenplatte, die auf Förderbandrollen transportiert wird
© Fraunhofer WKI | Bastian Weiß
Extrusion of flame-retardant façade panels on the basis of wheat straw and polyethylene
Probestück eines pflanzenreststoffverstärkten Kunststoffprofils, das in einen Ständer eingespannt ist und mithilfe eines Kleinbrenners beflammt wird
© Fraunhofer WKI | Jan Dannenberg
Small-burner test
Kleine Anlage zur Freibewitterung auf einem Hausdach, bestückt mit zwölf Profilstücken
© © Foto Fraunhofer WKI | Jan Dannenberg
Outdoor weathering of co-extruded profiles for determination of the durability of the flame-retardant effect

Project partners

  • Institute of Building Structures and Structural Design (IKTE) at the University of Stuttgart (Coordinator)
  • Profine GmbH
  • ETS Extrusionstechnik Mathias Stange


/etc/designs/default/0.gifFunding body:
German Federal Ministry of Food and Agriculture (BMEL)

Project management:
Fachagentur Nachwachsende Rohstoffe e. V. (Agency for Renewable Resources, FNR)

Funding reference:

01.10.2017 to 31.03.2020