Investigate the Potential for the Recycling of Carbon Fibre Composites by Solvolysis at Atmospheric Pressure
Principal Investigator: Prof S Pickering
Co-investigator: Prof P Licence
Project start date: April 2015. Duration: 6 months.
Context, aims and objectives
Carbon fibre reinforced plastics (CFRP) are ideal lightweight structural materials for aerospace, automotive, energy and sports industries and the global demand for carbon fibre, used almost exclusively in thermoset polymer composites, is forecast to grow from 46,000 tonnes in 2011 to 140,000 tonnes by 2020. Carbon fibre is a high value material that is energy intensive to manufacture and affordable technology to recover and recycle it from manufacturing waste and end of life components is required to improve its sustainability. A number of companies have emerged in the past five years or so operating commercially in carbon fibre recycling. These include ELG Carbon Fibre in the UK, MIT-RCF in the USA and CFK Valley Stade Recycling in Germany. The carbon fibre recovery processes used by these companies are based on pyrolysis at temperatures typically excess of 500ᵒC. A similar high temperature process based on fluidised bed technology has also been developed at The University of Nottingham. These processes are characterised by oxidation of the polymer matrix, with the potential for energy recovery and, in the case of the commercially operating pyrolysis processes, difficulty in uniformly removing all the pyrolytic char by oxidation without causing significant oxidation damage to the carbon fibre. The fluidised bed process produces a more uniformly clean recovered carbon fibre, but there is some oxidation, resulting in significant reductions in fibre mechanical strength.
This feasibility study proposes investigations into a novel recycling process for carbon fibre composites (CFRP) involving solvolysis at atmospheric pressure. Solvolysis processes are the next generation of carbon fibre recycling technology as they offer the recovery of chemical products from the polymer as well as the recovery of high grade carbon fibre with minimal degradation. Current published work on solvolysis shows processes that either require high pressures, typically over 50 bar, or lower pressure processes that require extended reaction times, typically over 10 hours. The use of alternative solvents that can process at atmospheric pressure and recover high grade carbon fibre in a matter of minutes is therefore very attractive. This step change in technology will address a key challenge in the adoption of recovered carbon fibre in manufacturing: the reduction of carbon fibre recovery cost.
The aim of the feasibility study is to investigate the potential for using solvolysis processing at atmospheric pressure for the recovery of near virgin quality carbon fibre and chemical products from waste carbon fibre composites. Specific objectives are to:
- identify liquids that are likely to be inexpensive and are effective in removing the polymer from the carbon fibre.
- establish that the polymer can be removed from the carbon fibre within a short time leaving clean individual filaments that lend themselves for manufacture into high grade applications as structural reinforcement.
- characterise the polymer products that are recovered and the quality of the recovered carbon fibre.
- devise a process concept that could be scaled to commercial operation.