Abstract
Management of waste from carbon fibre composites has become a significant societal issue as the application of composite grows across many industries. In this study, carbon fibres (CF) were successfully recovered from cured carbon fibre/epoxy (CF/EP) prepreg under microwave pyrolysis at 450, 550 and 650 °C followed by oxidation of any residual char. The recovered fibres were investigated for their tensile properties, surface morphologies and the elements/functional groups presented on the surface. The chemical compositions of gaseous and oil pyrolysis products were also analysed. The microwave pyrolysis effectively pyrolyzed the epoxy (EP) resin. Char residue remained on the fibre surface and the amount of char reduced as the pyrolysis temperature increased. Compared to virgin fibres, the recovered fibre suffered from a strength reduction by less than 20%, and this reduction could be mitigated by reducing the pyrolysis temperature. The surface of recovered fibre remained clean and smooth, while the profile of elements and functional groups at the surface were similar to those of virgin fibres. The main gaseous products were CO, H2, CO2 and CH4, whilst the liquid product stream included phenolic and aromatic compounds.
Highlights
Carbon fibre reinforced plastic (CFRP) composite has been widely used in automotive industries, wind energy industries and other engineering applications due to its unique combination of low-weight, high elasticity and strength and good corrosion resistance [1,2,3]
Carbon fibres were extracted from cured carbon fibres (CF)/EP prepreg successfully under microwave pyrolysis process at the temperature of 450, 550 and 650 ◦C
Increasing temperature has a positive effect on reducing the char residue on fibre surface as well as increasing the yield of oil and gas products
Summary
Carbon fibre reinforced plastic (CFRP) composite has been widely used in automotive industries, wind energy industries and other engineering applications due to its unique combination of low-weight, high elasticity and strength and good corrosion resistance [1,2,3]. The excellent mechanical properties of carbon fibre reinforced thermoset composites and their increasing affordability means that industrial demand continues to grow rapidly [4]. To deal with the increasing thermoset composite waste, recycling technologies including fluidised bed processes, solvolysis and pyrolysis have been proposed and demonstrated technical feasibility [6]. The major advantage of this process is being capable of dealing with contaminated composite wastes, but the polymer matrix is only burnt off for energy recovery. Solvolysis enables the recovery of clean fibres as well as recycles the thermoset matrix as a monomer phase [10]. Solvolysis remains energy intensive and requires organic solvents such as ethanol or propanol. The process is limited to laboratory scale, and it is difficult to generalise solvent selection for mixed waste streams [11]
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