Fibre composite breakthrough

Germany’s Fraunhofer Institute claims a material milestone in the development of bio-based fibre composites

Thanks to their wide range of possible applications, traditional fibre composites are popular materials in manufacturing – despite their relatively high production and disposal costs. However, the drawbacks can now be circumvented thanks to the development of a new, self-reinforced composite material made of polylactide (PLA).

Bio-based, easy to recycle and cheaper to produce, the material is said to be ideal for use in sporting, automotive and medical applications. A thermoplastic bio-polyester, PLA is made using lactic acids, renewable resources from agricultural waste, or specially cultivated raw materials such as sugarcane.

“In this project, we’ve brought the benefits of PLA to the next application level by fusing two types of polylactide to create a self-reinforced composite,” says Kevin Moser, project manager at Fraunhofer ICT.

He says the material combines the advantages of PLA with those of composites. “It has high mechanical strength and rigidity, while also exhibiting good hydrolysis resistance. Like pure PLA, the material is fully bio-based, easy to recycle, ductile and even industrially biodegradable.”

Advantages include substantially reduced manufacturing costs, since energy demands for PLA production are about half of those needed to manufacture petroleum-based plastics such as polypropylene and polycarbonate.

Additionally, recycling is simple since fibres do not have to be separated from a matrix – an issue that makes the recycling of conventional fibre-composite materials much trickier.

“The material, which can be manufactured on an industrial scale, represents a milestone in the development of functionalised, bio-based material systems with high mechanical strength,” Moser maintains.

“Also, it makes 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.”

In the manufacture of the composite, two different PLA types with different melting points are combined into a self-reinforced 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.

Apart from the Fraunhofer Institute, other partners in the project – which is funded by the European Union – include the Technical University of Denmark, the Belgian textile research institute Centexbel and the Danish firm Comfil.

The resource-conserving concept with great application potential also impressed the jury at JEC 2019, Europe’s largest trade fair for composite materials, winning first prize in the sustainability category.