As the volume of nonbiodegradable carbon-fiber-reinforced plastics (CFRPs) grows worldwide, there is also a growing concern in the UK composite industry about the huge amounts of waste generated by both manufacturing processes and end-of-life products themselves. Thermoset CFRPs, such as those produced with materials from the FibreCycle project, are usually recycled using one of three different processes: pyrolysis, solvolysis, or fluidized bed.
Pyrolysis, which can be either a continuous or batch process, involves burning off resins with a very limited amount of oxygen. Recycled fibers can be sold in milled, chopped, or pelletized form. Microwave pyrolysis processes are also being developed in the US, Germany, and the UK.
During solvolysis, both the resin and the fibers are recovered. High temperature and high pressure are required to reach a supercritical state, and the process uses fluids such as water, propanol, or methanol.
In the fluidized bed process, both cured and uncured composite wastes are fed into a bed of sand and exposed to hot air, which breaks down and vaporises the polymer. The resin products are fully oxidized in a combustion chamber, where the heat energy can be recovered. Fibers and filler are carried out of the bed by way of the gas stream.