The growing use of carbon and glass fibres has increased awareness about their waste disposal methods. Tonnes of composite waste containing valuable carbon fibres and glass fibres have been cumulating every year from various applications. These composite wastes must be cost-effectively recycled without causing negative environmental impact. This review article presents an overview of the existing methods to recycle the cumulating composite wastes containing carbon fibre and glass fibre, with emphasis on fibre recovery and understanding their retained properties. Carbon and glass fibres are assessed via focused topics, each related to a specific treatment method: mechanical recycling; thermal recycling, including fluidised bed and pyrolysis; chemical recycling and solvolysis using critical conditions. Additionally, a brief analysis of their environmental and economic aspects are discussed, prioritising the methods based on sustainable values. Finally, research gaps are identified to highlight the factors of circular economy and its significant role in closing the life-cycle loop of these valuable fibres into re-manufactured composites.
Interest in natural fiber-reinforced polymer (NFRP) composites is growing rapidly in the transportation sector, especially as a replacement material for metals and synthetic fiber composites. The heightened interest is directly related to a need to produce lightweight and fuel efficient vehicles. Further, stringent legislation and greater environmental awareness is forcing transportation industries to select materials with a smaller carbon footprint. In such a context, NFRP composite materials are a good choice due to their low cost, low environmental impact, and relatively equivalent properties to metals and other composites. Most prior studies have examined commodity plastics such as polypropylene, polyethylene, and epoxy as the primary polymer matrix in NFRP composites and little work has addressed engineering plastics. Engineering plastics, which includes polycarbonate, polyamides, and polystyrene, are high performance thermoplastics with superior properties but relatively higher cost than commodity plastics. It has been claimed that even after recycling, engineering plastics properties are superior to those of commodity plastics, and thus, utilization of recycled engineering plastic in NFRP composites can help reduce waste and lower composite material costs. The aim of this review article is to explore the current status of engineering plastics reinforced with natural fibers such as flax, hemp, jute, and sisal and to examine their use in automotive, aerospace, and maritime applications. Properties and processing techniques of engineering plastics reinforced with natural fibers are also studied.
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