Pyrolysis, or the decomposition of a substance using heat, is the best way of recovering carbonfibre from recycled composite structures, according to the non-profit Metallurgical Research Association of the Basque Country in San Sebastián, Spain.
Industrial interest in the environmental impact of dismantling aircraft led the centre to investigate carbonfibre recycling. The association investigated two processes for reclaiming carbonfibre from composite structures. One process uses nitric acid to dissolve the resin used to hold the fibres togther in a composite structure. The carbonfibre is then washed in water three times and once in acetone for its recovery.
The second process is the pyrolysis method. This involves putting materials in an argon atmosphere that is heated to melt the resin, while the carbonfibre is unaltered.
While researchers found that recycled carbonfibre from both processes could still provide strength enhancement for materials, they concluded that pyrolysis produced the best quality recycled carbonfibre.
In particular, tests with thermoplastic composites provided enhanced mechanical properties. The study included an analysis of the environmental qualities of the process.
The need to heat the nitric acid and its innate toxic properties counted against it. The process generated more toxic residue than material originally processed. The cost estimates for both processes assumed the waste composite structure was free.
A third process that was tested was the incineration of the waste composite structure and the use of the resultant heat for power generation.
Source: Flight International
