Materials

How recyclable are composite plastics?

How recyclable are composite plastics?A new report has been launched to highlight currently available recycling methods for processing composites, such as carbon and glass fibre materials, and includes suggestions for making them commercially viable.

The report, ‘Composites Recycling – Where are we now?’, was produced by Composites UK, a trade body for the composites industry, in collaboration with the Universities of Manchester, Nottingham and Birmingham. It includes details on fibre reinforced polymers (FRP) and recyclable resins, processes used in their recovery and reuse, the environmental impact of composite recycling, applications for dry fibres and associated legislation.

The composition of FRPs gives them strength and durability but they remain lightweight making them useful across a wide range of industries. Indeed, their use is increasing around the world, with the global market for products expected to reach US$95 billion (£71.6 billion) by 2020.

It is these properties, however, that also makes them difficult to recycle and the increase in products made out of the materials also means there is an increased need for sustainable recycling options for these materials.

Although still a relatively small waste stream, it is estimated that 2,000-3,000 tonnes of carbon fibre reinforced polymer (CFRP) waste and up to 60,000 tonnes of end-of-life glass reinforced polymer (GRP) waste are produced in the UK each year.

Although processes have been developed to recycle these materials, few have become commercially available. To make them more available new business models are needed that integrate with existing waste management supply chains, according to the report.

Composite polymers

The report focuses mainly on the recycling of thermoset FRPs, which are plastics reinforced with fibres, commonly glass or carbon, and some thermoplastic materials.

Thermoset composites become hard when heated and can’t be remoulded once formed, while thermoplastic materials are the opposite, softening when heated and becoming hard when cooled.

GRPs are relatively hard to recycle but can be used as a refuse derived fuel in energy from waste methods. Another process that can be used to recycle GRPs is solvolysis, which involves heating the material to 200°C under pressure to allow intact fibres to be recovered.

To highlight the use of this process, Gary Leeke from Cranfield University, brought a two-person carbon-fibre kayak, made from recycled carbon fibre to Composites UK’s circular economy event this month, which coincided with the report launch. Presentations at the event showcased research into increased fibre alignment by the Universities of Bristol and Nottingham and Tilsatech, a producer of flame retardant materials.

Minimising ‘negative environmental impact’

Stella Job, Supply Chain and Environmental Manager at Composites UK, said: “It is important for Composites UK as a trade association to work with our own industry and the waste management sector to minimise any negative environmental impact and gain the best value from our waste.

“We are committed to supporting new processes and supply chains which will help us achieve this. We heard from several of the organisations we are working with at our event last week: ‘A Circular Economy for the Composites Industry’, with a backdrop of ELG’s shredding and sorting facility.”

More information can be found in the ‘Composites Recycling - Where are we now?’ report on the Composites UK website.