New recycling technology provides end-of-life solution for composite plastics

Automotive and construction industries are set to benefit from a commercially viable route towards sustainable manufacture. New technology based on pyrolysis and physical separation could tackle a growing problem for automotive, construction and other major industries – how to recycle composite plastics.



Forthcoming legislation sets increasingly stringent targets for recovery of composite materials, used for highly engineered components such car bumpers and fascias. The high tech plastics are lightweight and durable but relatively difficult to recycle. The EU end-of-life Vehicle Directive requires 85% recovery of plastics, rubber and glass by 2006 and 95% by 2015. Fibre-reinforced composite plastics are widely used in automotive, construction and other industries. Around 240,000 tonnes a year are produced by UK industry. Composites are strong, lightweight and readily engineered into complex components.



Fibre-reinforced composites are more difficult to process than other plastic waste materials such as polythene. They cannot simply be melted because they are thermoset and contain a significant fraction of glass or other fibre and filler such as calcium carbonate. Components are often bulky and uneconomic to transport. Scientists from the University of Leeds, working with partners from British industry, have come up with a solution that could divert growing quantities of composites going to landfill. The two-year research project formed part of a major waste minimisation initiative backed by government and industry. The WMR3 LINK programme (Waste Minimisation through Recycling, Recovery and Re-Use in Industry) is spearheading new ways to clean up the environment and make better use of resources.



‘Until now, fibre-reinforced polymer composites have been widely considered un-recyclable,’ says Professor Paul Williams of the University of Leeds, Department of Fuel and Energy. ‘That has been a major headache for the motor industry in particular. Most of the car, including the tyres, metal and glass can be recycled quite easily but composites are much more difficult because the material is reinforced.’



The new recycling process combines pyrolysis and physical separation. Composites are broken down into gas, oil, a small amount of carbon and fibre. Recycled oil and fibre can both be re-processed into composite plastics. Pyrolysis operates at a low temperature, around 500oC, so recycled fibre retains its size and much of its strength. After cleaning, up to 25% of recycled fibre can be combined with 75% virgin fibre in new composite plastics without any deterioration in product quality. Results show that recycled fibre can be woven into cloth and sprayed with resin to build structures such as boat hulls. Use in fibreboard is also being investigated.