Researchers at the Fraunhofer Institute for Applied Polymer Research (IAP), based in Potsdam, Germany, have received funding to develop new reinforcing PLA fibres for composites.

The challenge is that conventional PLA has a relatively low temperature resistance and technical fibres can be produced most economically using the melt spinning process.

The Fraunhofer IAP team has developed more thermally stable stereocomplex PLA (sc-PLA), in which the PLA molecules form a special crystal structure. This allows the production of fibres which have a melting point that is 40-50°C higher than conventional PLA fibres.

The researchers are now working with fibre producer Trevia to optimise a melt spinning process for sc-PLA filament yarns.

In addition, the development of a manufacturing process for sc-PLA reinforced flat films is planned and the team will work with adhesive tape manufacturer Tesa to test the suitability of sc-PLA films as adhesive foils. Fraunhofer IAP also plans to process the filaments in a double pultrusion process to produce granules suitable for injection moulding.

“We are further developing our PLA fibres in order to transfer them to industrial scale together with partners from industry,” said project leader Dr André Lehmann. “These fibres are ideally suited for reinforcing PLA plastics. The resulting self-reinforcing single-component composite promises great recycling benefits because since the fibre and the matrix of PLA are chemically identical, complex separation steps are not necessary.

“The automotive and textile industries are already showing interest in bio-based materials that are easier to recycle. In terms of price, PLA would already be competitive.”

The research is being funded by the German Federal Ministry of Food and Agriculture (BMEL) which is intensively promoting the development of biomaterials, with more than 100 projects currently underway.

www.iap.fraunhofer.de