Society’s desire to have ‘more for less’ has led to a surge in products – from planes to phones – being manufactured from increasingly complex materials.

New-generation planes, for example, are significantly lighter than previous airliners, making them more economical and thus enabling airlines to cut airfares.

There is a downside, however: These new, composite materials such as fibre-reinforced polymers are non-biodegradable and, at the moment, unrecyclable – so what do we do with the products when their serviceable life is over?

The answer, at the moment, is ‘nothing’ – or at least nothing useful or environmentally friendly. Two researchers at the School of Chemical Engineering are hoping their groundbreaking work in this little-known field will change that, leading to the global recycling of materials like glass and carbon fibres.

Dr Gary Leeke, Reader in Low Carbon Technologies, and Research Fellow Dr Géraldine Oliveux have recently had their paper on the subject, ‘Current status of recycling of fibre-reinforced polymers’, published in the prestigious peer-viewed journal Progress in Materials Science.

Co-written with former University colleague Luke Dandy, who now works for BAE Systems, the paper has already attracted a raft of interest from America and Europe.

‘The paper is about the recycling of materials that are not considered recyclable at the moment,’ explains French-born Géraldine. ‘There is a company in the UK that does some recycling of these materials, using a heat process, but not in a “circular” way: we’re looking at an holistic approach to the recycling of everything that is present in carbon and glass fibre and other fibre-reinforced composites.’

It is the strength and durability of carbon fibre – most notably used to reinforce composite materials – that has made it so popular in the aerospace, civil engineering and motorsports industries. When combined with a plastic resin and wound or moulded, it forms carbon fibre-reinforced polymer, which boasts a very high strength-to-weight ratio, and is very rigid as well as lightweight.

‘The downside is that this material is not biodegradable, so when a product’s use comes to an end, what do we do with it?’ asks Gary.

When you think that an A380 airbus contains 50 per cent of this kind of material in weight, you can’t just leave it, because it will sit there forever. So our paper looks at recycling and the technologies available to do this.

At the moment, such materials go to landfill or are incinerated, but the exponential growth in the use of fibre-reinforced polymers means alternative solutions need to be found.

‘Everyone wants to fly further, more cheaply, so for that we need more lightweight planes, which means using more composite materials,’ says Gary. ‘So in 10-15 years’ time, when the new-generation planes come out of service, we need to know what to do with them.

‘There is so much more waste being produced due to the fact that we’re making more complex products all the time: take mobile phones, for instance – we’re upgrading them every couple of years.’

One way to recycle composite materials is to separate the components. ‘If composites are stripped back to their original materials, we can look at their properties and how they can be reused, balancing economic and environmental issues.’

In their paper, Gary and Géraldine explore a range of different possible options, from mechanical recycling to a process they have developed called solvolysis, a chemical treatment using a solvent to degrade the resin that binds composite materials.

The researchers, who are currently working on the recycling of composite materials in the framework of the EPSRC-funded project EXHUME (Efficient X-sector use of HeterogeneoUs MatErials in Manufacturing) in collaboration with the universities of Exeter, Cranfield and Manchester, say the intervention of government is vital if industry is to take the issue seriously.

‘As well as discussing this in the published paper, we will also be putting out a White Paper to the Government at the end of the EXHUME project,’ says Gary.

‘More effort needs to be put into developing new practices. At present there are no official standards for this kind of waste, which prevents it being recycled. There is interest from industry, but it needs to lobby the appropriate bodies to get standards approved, so that it’s possible to sell a recycled product that has quality assurance attached to it.’

Géraldine adds: ‘If that were to happen, it would generate a new economy through the recycling of fibre-reinforced polymers. If my mobile phone case was made from part of an A380, or my pencil or knitting needles came from a Formula One car, I’d like that – and kids would find it cool.’

  1. This paper, titled ‘Current status of recycling of fibre reinforced polymers’ was originally published in ‘Progress in Materials Science volume 72’.
  2. The paper also received the College of Engineering and Physical Sciences Best Publication award for April 2015.