Stable and circular: Thermally stable self-reinforced PLA composites

Fraunhofer CCPE researchers are investigating composites made of thermally stable PLA filaments and a chemically identical matrix. In recycling processes, these materials have a clear advantage over established fibre-reinforced systems and thus offer an option to contribute to the UN Sustainable Development Goals.

The material class of conventional, petroleum-based polyesters, with polyethylene terephthalate (PET) as the main representative, has dominated the fibre market for many decades and is applied in both textile and technical segments. With the bio-based and biodegradable representative polylactic acid (PLA), on the other hand, the relatively low melting temperature of approx. 170 °C limits the potential areas of application. This weakness can be remedied if stereocomplexation is exploited, which makes it possible to increase the melting temperature by approx. 60 K. In the past years, the research community has mainly dealt with this topic on a laboratory scale, resulting in stereocomplex PLA (scPLA) based products not being commercially available up to now. The implementation of the manufacturing process for scPLA fibres using the economically viable melt spinning process is welcomed by the industry, by both leading European material and fibre manufacturers, as it is expected to significantly expand the areas of application for PLA-based materials.

Even greater potential lies in the development of PLA-based single-component composites that this will enable. The increased melting point of the scPLA fibres allows them to be incorporated into a chemically identical PLA matrix. This can generate an advantage over established fibre-reinforced systems with regard to the recycling process and contribute to the implementation of the UN Sustainable Development Goals.

After two years of research activity within the Fraunhofer CCPE, the scientists succeeded in implementing a manufacturing process for scPLA fibres in order to be able to produce sample quantities on a kg scale in the spinning pilot plant at the Fraunhofer IAP. These developments were crucial to enable the currently ongoing cross-institute research. Here, fabrics made from scPLA-PLA blended yarn are being formed into self-reinforced organic sheets at the Fraunhofer ICT to verify the reinforcement effect and initiate the development of PLA-based single-component composites for technical components. In addition, a cooperation of the Fraunhofer IAP with Trevira GmbH as well as tesa SE will start on 1 June 2021 within the framework of a BMEL-funded project. The aims of the joint research project are to transfer the manufacturing processes for scPLA fibres and films to industrial production facilities and to develop self-reinforced PLA granulate for injection moulding applications.

Contact person:

Dr. Evgueni Tarkhanov (evgueni.tarkhanov@iap.fraunhofer.de)