|Catalytic conversion technologies to recycle carbon fiber combining three different processes have been developed by Adherent Technologies Inc (ATI) of New Mexico, USA. ATI has evolved a catalytic conversion technology centred around its batch-based carbon fibre recyclate processing, combining three different processes studied over the past decade, each with specific advantages and limitations. ATI has demonstrated its low-temperature wet process in combination with vacuum pyrolysis for the removal of insoluble contaminants in a pilot-scale reactor capable of processing 23 kg (50 lbs) an hour. Testing of the recycling technology on CFRP scrap with multiple resin chemistries indicates that the combination of dry and wet processes is the best way to maximise recyclate quality.
Vacuum pyrolysis, a dry process operated at around 500°C (932°F), recovers resins as marketable liquids and can be easily up-scaled. At this temperature, however, fibre product may retain oxidation residue or char. The company�s low-temperature liquid process operates at 150°C (302°F), runs at less than 150 psi on standard equipment, and produces a market-ready fibre, but is not particularly tolerant of scrap contaminants (such as metal, wire, paint and sealants). The high temperature liquid option (around 300°C/572°F) produces clean fibres from most composites, but requires customised equipment and is currently not considered necessary for commercial recyclate production. Phenol has proven a good choice as initial heat transfer fluid for both wet processes; the breakdown products of the resin can be recycled into glue for the production of plywood.
As per Reinforcedplastics.com, low temperature wet chemical processing removes the bulk of the resin and some contaminants, followed by thermal post-treatment through vacuum pyrolysis to eliminate remaining resin and produce 99% fibre purity. This may not result in the most elegant processing, but it is capable of handling the true mixed soup of CFRP waste without the need for time-consuming and expensive hand sorting, making it financially viable. Further, the combined approach eliminates the need for any solvent use.