Bio-SRPC - Development of biobased self-reinforced polymer composites
In all-polymeric composites, the reinforcing and matrix phases are composed of suitable polymers. In self-reinforcing polymeric composites (SRPC), the same polymer or polymer family forms both the reinforcing and the matrix phases. SRPC offer enhanced performance when compared to traditional composites due to their lower densities, reduced use of fillers and additives, superior impact properties and better recyclability.
The aim of the project is to develop production routes for 100 % bio-based self-reinforced polymer composites. The developed bio-based self-reinforced polymer composites (SRPCs) will have mechanical properties which are comparable to the commercially available oil-based equivalents. The approach is to develop multi-component SRPCs, by combining PLA grades with different melting points. From processability point of view this offers the best potential since larger operating windows can be defined.
As the first step in the BioSRPC project, the tenacity and modulus of PLA filaments were increased. A PLLA grade with a low D lactic acid content showed to be optimal for obtaining high mechanical properties. For monofilament tapes, this resulted in a tenacity of 0.45 N/tex, for multifilaments a tenacity of 0.50 N/tex was obtained applying a 2 step process. These high strength PLA filaments are not only of interest for further use in composites, but they also have potential to be used as high performance fibres in technical textiles.
The processing of the obtained filaments to textile structures was the next step within the process chain. Non-woven production was fast and resulted in a flexible textile structures. Weaving of the PLA filaments was more challenging, yet multifilament yarns could successfully be processed into narrow fabrics. Further optimisations are needed to upscale this efficiently to broader fabrics.
As a final step, self-reinforced PLA composites were produced out of the PLA filaments and textile structures. Based on the described result, it can be concluded that by self-reinforcing PLA, the modulus of PLA can be more than doubled, while strength of 160 MPa is reached. Impact resistance can be at least multiplied by a factor 5, increasing the toughness of brittle PLA. Moreover, the composites have properties that are competitive or higher than CURV (SRPC from polypropylene), even when taking into account the materials density. PLA SRPCs show potential for application in semi-structural applications.