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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - BIO4SELF (Biobased self-functionalised self-reinforced composite materials based on high performance nanofibrillar PLA fibres)

Teaser

Summary

The worldwide demand for replacing fossil-based raw materials by biobased alternatives has led to a significant growth of technological developments on bioplastics. Polylactic acid or PLA is considered as one of the most promising biobased polymers and is currently being used the most.
However, there still exist drawbacks that prevent the wider use and commercialisation of biobased materials such as PLA. The 2 most important ones are:
- Lower mechanical performance: although PLA can already replace conventional materials for quite some applications, its limited mechanical strength is still hampering commercial applications.
- Limited durability: for applications with long lifetime, PLA is not optimal yet due to its limited hydrolytic stability.
Tackling of the current drawbacks remains an important challenge for biobased polymers. There is a need to develop biobased, sustainable polymeric materials with high stiffness, high impact and high durability without impairing recyclability.
The BIO4SELF project wants to tackle these drawbacks and aims at fully biobased self-reinforced polymer composites. These are based on two PLA grades, one to form the matrix and a high stiffness one to form the reinforcing fibres. For reaching the unprecedented stiffness, PLA is combined with a bio-LCP (Liquid Crystalline Polymer) to create an extra reinforcement level. Furthermore, the temperature resistance of PLA and its durability is being improved. The latter via adding well-chosen anti-hydrolysis agents. Also the effect of crosslinking is under evaluation. Further, odour reduction combined with inherent self-functionalization via photocatalytic polymers (self-cleaning properties), tailored microcapsules (self-healing) and deformation detection fibres (self-sensing) will be added. The potential of the biobased self-reinforced materials will be proven in advanced prototypes for automotive and home appliances.
BIO4SELF aims at cost-efficient production of sustainable and fully biobased composites with high technical performances. The use of PLA in the novel composite parts will represent a major contribution to the sustainability of the final products, drastically lowering the environmental impact. To reach this goal, the whole value chain is represented within BIO4SELF, as schematically presented in the value chain (see figure), and innovations all along this value chain are necessary. More specifically this is translated into the following key objectives:
- Novel PLA compounds, with various functionalities, for the high melting reinforcement fibre and the low melting matrix
- High and low melting PLA filaments fulfilling the required properties for the composite processing steps and resulting composite performance
- Production of composite intermediates combining the low and high melting PLA materials (hybrid yarns, woven fabrics, UD tapes and reinforced pellets)
- Demonstration of the PLA composite in prototypes of the projectâ€™s end users, produced either via compression moulding, injection moulding and/or thermoforming
Parallel to these activities, a detailed sustainability and cost assessment combined with market analyses and the set-up of business plans are being performed, as this knowledge is vital to allow the fast adaptation of the results towards industry.

Work performed

From research side, the main focus in the past period was given to the development of the PLA compounds, their processing into filaments, the production of composite intermediates and transferring these intermediates to first composite parts.
An important first step regarding the development of novel material formulations and the related processes was the selection of PLA grades. Further, results were obtained regarding PLA compounding, development of microcapsules for self-healing, additives for self-cleaning and for conductivity, the latter aiming at self-sensing compounds. Both commercially available liquid crystalline polymers (LCPs) and bio-based LCPs made on lab scale were successfully blended with PLA. Also first large scale compounding trials have been performed.
As a next step, filament extrusion of the PLA compounds into filaments was performed. This started with optimisation of the process for unmodified PLA materials and was later broadened to functionalised compounds. Filaments were also extruded on larger scale making further processing to composite intermediates possible.
Different types of composite intermediates will be developed. Focus so far was given to hybrid yarns and woven fabrics. Tests have shown a good intermingling of reinforcing and matrix fibres in the hybrid yarns at high production speeds. Woven fabrics were successfully produced using these novel hybrid yarns. Preliminary tests were done for making PLA pellets reinforced with PLA fibres.
Subsequently, the developed materials were evaluated in simple composite parts, with a dual aim: providing feedback to the material developments in the previous steps and recommendations for the prototype production in the next step. First PLA self-reinforced composite plates were successfully made and characterised.
Finally, even though not yet officially planned, already some first early â€˜baselineâ€™ prototypes were made from PLA by the BIO4SELF end users.

Final results

Self-reinforced polymer composites based on standard fossil based polymers already reached full maturity with various products on the market. The feasibility of self-reinforced biobased polymer composites out of two PLA grades with different melting temperatures is already proven within BIO4SELF at pilot scale and even at industrial scale for one of the end use cases. Further developments will focus on increasing the performance level of the composites and adding functional properties.
One of the routes to improve the performance is the reinforcement of PLA with liquid crystalline polymers (LCPs). BIO4SELF wants to transfer this LCP technology to biobased materials, both by reinforcing PLA with standard commercially available LCPs as well as by the development of bio-LCPs.
Also crosslinking of PLA via radiation will be studied to raise the PLA properties. Within BIO4SELF we will transfer and upscale the radiation technology towards PLA.
Self-functionalizing properties will be added to the PLA based materials. Microcapsule-based self-healing systems for PLA are well described in literature and are being adapted for application in self-reinforced composites. Photocatalytic blends can exhibit high self-cleaning efficiency as demonstrated at lab scale for polypropylene. Here, the technology will be adapted with PLA and up-scaled. Conductive CNT compounds have been successfully demonstrated as smart sensors for strain measurement in injection moulded parts.
Becoming more biobased is a key EU priority. BIO4SELF will contribute to this by bringing innovative high value high volume components from fibre-based materials on the market at competitive pricing and made from non-fossil sources using mainly existing industrial scale equipment.