The recyclability of parts is becoming an increasingly important issue in car design. This applies for example to reinforcement of the body panel between the bonnet and the front windscreen. It is crucial in assuring the safety of pedestrians in the event of an accident, and must therefore satisfy very specific mechanical requirements. The Spanish tier 1 producer Maier currently makes this part from a combination of polypropylene and fibreglass.
‘You can use PLA as raw material for the petrochemical PP as well as the fibreglass. This biobased version supplies a huge advantage when it comes to durability, while its mechanical and functional properties are at least equal to those of composites based on PP. What’s more, it is a mono-material, which makes it much easier to recycle,’ states Guy Buyle, coordinator of BIO4SELF, which was established on 1 March 2016.
BIO4SELF builds further on existing expertise in SRPCs, including that of one of the initiators and coordinator Centexbel, the Belgian research centre for textile and plastics, where Guy Buyle works as European project manager. ‘Besides making new blends and their characterisation, together with end users we want to end up with real applications in this project. One of those parties is Maier, which already has a real application in mind for the PLA composite materials: they can serve as a stiff and shock- absorbing material for certain vehicle parts. Another example is the Turkish home appliance manufacturer Arcelik. They have specified a number of components, but will determine the actual applications at a later stage, depending on the properties we can obtain with the composite materials,’ according to Buyle. This will also depend on the temperature to which the new components can be exposed. For PLA that has been limited thus far to around 50 °C. ‘One of the aims is to improve that specification. We also want to create more generic products, which can be put to a wider range of applications than just with the partners in the programme. We want to show what you can do with 100 percent biobased materials and we want to urge businesses to use them.’
An important condition of the large-scale production of the PLA-based SRPCs is that the polymers can be processed with the existing production equipment. ‘The concept of material reinforcement is clear, but we have to see how that performs in the value chain and optimise it even more, for example by adapting process parameters,’ according to Guy Buyle.
AMIBM and partners
A major role is set aside in the BIO4SELF project for the international research institute Aachen-Maastricht Institute for Biobased Materials (AMIBM) set up at the end of last year at the Brightlands Chemelot Campus. This joint venture between Maastricht University, RWTH Aachen University and Fraunhofer IME has a research programme aimed at the sustainable and efficient production of biobased materials and their innovative application in medical and technical applications. Of the €6.7 million subsidy awarded to BIO4SELF, almost €1.2 million is destined for the partners Maastricht University and RWTH Aachen of the AMIBM.
Because businesses from the entire value chain are involved with the partners in the BIO4SELF project, the expertise of AMIBM employees can also be put to use directly in practice. For instance, there are companies that engage in extrusion, twining, spinning, injection moulding and thermoforming, all separate processes that need to be optimised for the biobased composite materials. ‘The advantage of this chain-wide cooperation is that when there is a success, a production chain is immediately ready for large-scale products, and we can have a significant impact on the market with large end customers such as Maier and Arcelik,’ says Guy Buyle.
Dietmar Auhl, lecturer in the ‘biobased materials’ research group and project leader at AMIBM for BIO4SELF, explains how AMIBM wants to add value to the Horizon 2020 project. ‘We have a great deal of experience in polymer research, materials and process design. Our multidisciplinary team covers the entire value chain starting from biobased materials, and can contribute fundamental expertise to every phase. The selection of the PLA raw material and ideas about existing grades or variations within it are crucial steps you need to take before you can make a start on processing and product design. We improve practical research with (simulation) models, which enables us to design materials, processes and products even more efficiently.’
It is highly likely that in the coming five years it will not be possible to compete with the classic SRPCs on the basis of the raw material prices, unless the current low prices of oil and raw materials derived from oil change fast. ‘But you have to consider that SRPCs are not used much at all yet anyway, that the concept has not been fully developed yet, not for the classic polymers either. By achieving that further development in this project for biobased SRPCs, we can develop excellent alternatives for conventional solutions, based on mechanical and functional properties’, argues Guy Buyle.
On the basis of the deliverables from BIO4SELF alone, he estimates that in three or four years there will be a market of 35 kton/year for PLA-based SRPCs. ‘But it can be a lot more than that, if I just go by the interest of the now five companies that have joined the Innovation Support Group, for example because they are interested in testing materials. When you know that IKEA is one of the parties showing interest, the impact of biobased SRPCs could become quite a lot bigger.’
Playing with chains and fibres
The production of self-reinforced PLAs boils down to combining two different PLA polymer fibre types. The matrix requires one PLA with a relatively low strength and melting temperature, while the other polymer, like PLA, has to have great strength and high melting temperature. When you combine the two starting substances, at a particular pressure and particular temperature the polymer with the low melting temperature will melt and form the matrix, while the other one remains intact and adds strength to the material.
The properties of the final composites are determined by different factors. For instance, you can vary the ratio between the two polymers (blends) and vary the length of the chains. In this project we will also attempt to create even stronger materials by combining PLA with biobased LCP (Liquid Crystalline Polymer). In addition, special additives can add all kinds of extra properties. As far as that goes, at BIO4SELF the focus is on three ‘smart’ functionalities: self-healing, cleaning and sensing. With self-healing, microcapsules are added to the polymer, which can cause a repairing polymer reaction. Cleaning involves the breakdown of certain components under the influence of light (UV) so that they can be rinsed off the material, along with the contamination that has attached to them. For sensing, conductive nanoparticles are added to the mix, which allows the material to be incorporated in an electrical circuit where it can detect interruptions, for instance. BIO4SELF also aims to use biobased materials for these additives as much as possible.