Bio-based composite sheets manufactured from two polylactide types with different melting points.

Project creates new self reinforcing bio-based composite material

A new self-reinforcing bio-based composite material developed as part of the Bio4self project and made from polylactide (PLA) claims to be easier to recycle and cheaper to produce than traditional carbon fibre composites.

A thermoplastic bio-polyester, PLA is based on lactic acids, renewable resources from agricultural waste, or specially cultivated raw materials such as sugarcane. In the Bio4self project, Fraunhofer researchers fused two types of PLA to create so-called self-reinforced PLA composites.

This combines the advantages of PLA and composite materials. The newly developed PLA composites have high mechanical strength and rigidity while also exhibiting good water resistance. Like pure PLA, they are fully bio-based, easy to recycle, ductile and even industrially biodegradable. It was possible to substantially reduce the manufacturing costs, and the energy demands of PLA production are now approximately half those needed to manufacture petroleum-based plastics such as polypropylene and polycarbonate.

Fibres and textiles made from polylactide.

In PLA, the CO2 equivalent per kilogram of material used is half that of products based on fossil fuels, such as polypropylene and polyester. Furthermore, recycling PLA composites is very easy, as they are made up of just one material type and the fibres do not have to be separated from the matrix – an issue that makes the recycling of conventional fibre composite materials much trickier.

These composite materials represent a milestone in the development of functionalized bio-based material systems with high mechanical strength. And they make a substantial contribution to the closed-loop economy, because the composite can also be melted and, using existing manufacturing equipment, reprocessed into a new product for high-quality applications. Kevin Moser, project manager at Fraunhofer ICT

In the manufacture of the composite, two different PLA types with different melting points are combined into a self-reinforced PLA composite material. The higher-melting-point PLA is embedded as a reinforcing fibre in the lower-melting-point matrix. The resulting material rigidity can compete with commercially available self-reinforced polypropylene composites. It is planned to manufacture initial prototypes already later this year.