Carbon fibre waste recycling breakthrough

Carbon fibres could be recycled for the first time, enabling firms to reuse components and cut down on production waste.

Carbon fibre composite materials consist of the fibre embedded in a resin matrix. They are used in such industries as aerospace and electronics, and at present the hi-tech material is thrown away when the product reaches the end of its life. This adds to the build-up of non-biodegradable waste. The new technique allows the fibres to be reclaimed from the matrix.

New fibre is expensive to produce. A great deal of the material is also currently wasted during production, said Dr Steven Pickering, a senior lecturer at Nottingham University, who is to lead a three-year research programme into the problems.

‘Carbon fibre users have trouble deciding what to do with cut-offs from production, and there is a similar issue with products that reach the end of their lives. But we don’t have to throw this hi-tech material away,’ he said.

Researchers at the university will use a recent invention, the fluidised bed, to remove the epoxy resin to enable the carbon fibre to be recycled. The ‘bed’ is actually a chamber containing sand, which acts like a fluid when suspended in an airstream. The chamber, and therefore the sand, is heated to 450 degrees C.

The carbon fibre is chopped into 2cm2 blocks and dropped into the bed. The epoxy resin evaporates and the fibre is blown by the airstream to a collection point.

It is the resin that has in the past prevented engineers from recycling carbon fibre, as it is a thermoset material that once heated and cooled into a moulded shape cannot be reheated and remoulded. Evaporating the resin allows the fibre to be reclaimed for further moulding, said Pickering.

‘The reclaimed fibre becomes fluffy like cotton wool, and our aim is to see this processed into a usable form,’ he said.

The reclaimed 1cm-long fibres have a number of applications, including use in injection moulding compounds, because of their ability to strengthen materials. But most existing manufacturing technology has been designed for use with long strands of the material, so the research team will be looking into ways of making the shorter recycled fibres compatible.

‘This might involve pelletisation, or producing the fibre in a more orientated form, so it is less fluffy. In this form it could be woven into tissue that can be worked into the standard material.’