Accelerated degradation of Polyetheretherketone (PEEK) composite materials for recycling applications

AbstractThe decomposition of Polyetheretherketone (PEEK) is carried out at 623 K within 30 min using a co-solvent system comprising of ethanol and water. It has not previously been possible to carryout the decomposition of PEEK below 703 K in aqueous media. Decomposition is achieved using catalytic quantities of caesium carbonate (Cs2CO3), as low as 19 μmol ml−1, in a high pressure bomb reactor. Carbon fibres are separated from a PEEK/carbon fibre composite and analysed by SEM-EDX. A reaction scheme is proposed for the decomposition process, producing phenol and dibenzofuran as major products. Phenol is analysed quantitatively by means of HPLC, the identification of decomposition products is performed by GC–MS. Decomposition of PEEK at 7 K above its melt temperature using Generally Recognised as Safe (GRAS) solvents represents a significant advance in the recycling of end-of-life, contaminated and deteriorated thermoplastic composite materials

Counting carbon fibres by electrical resistance measurement

AbstractElectrical Impedance Measurement has been used to measure the diameter of single carbon fibres to within 3% of the actual value measured by Scanning Electron Microscopy (SEM). The precision of the technique developed also allows for the accurate determination of the number of fibres present in a carbon fibre bundle, such data are important for the calculation of fibre tensile strength from the tensile force applied to carbon fibre bundles. The impedance of a single carbon fibre and carbon fibre bundles of up to 20 fibres have been measured, with results showing good agreement with theoretical values. The impedance of multiple lengths of carbon fibres ranging from 80 to 300mm has also been studied, with the impedance being directly proportional to the fibre length, as per electrical theory. This technique will be suitable for determining the number of fibres in a virgin or recycled carbon fibre bundle

Energy-efficient scheduling of flexible flow shop of composite recycling

Composite recycling technologies have been developed to tackle the increasing use of composites in industry and as a result of restrictions placed on landfill disposal. Mechanical, thermal and chemical approaches are the existing main recycling techniques to recover the fibres. Some optimisation work for reducing energy consumed by above processes has also been developed. However, the resource efficiency of recycling composites at the workshop level has never been considered before. Considering the current trend of designing and optimising a system in parallel and the future needs of the composite recycling business, a flexible flow shop for carbon fibre reinforced composite recycling is modelled. Optimisation approaches based on non-dominated sorting genetic algorithm II (NSGA-II) have been developed to reduce the time and energy consumed for processing composite wastes by searching for the optimal sub-lot splitting and resource scheduling plans. Case studies on different composite recycling scenarios have been conducted to prove the feasibility of the model and the developed algorithm