Purpose Carbon fiber, Kevlar® fiber, and glass fiber are the most widely used polymer prepregs in manufacturing high-performance composites to produce vital parts for a wide range of applications. The production of carbon and Kevlar® fibers is an energy-intensive process, requiring 198–595 MJ to produce 1 kg of virgin carbon fiber. However, chemically recycling these expired prepregs takes only 38.4 MJ/kg, which could be significantly sustainable. The work described in this study involves an array of experiments involving acid treatment of outdated prepreg composite fibers to study its effects and reclaim the fibers for future applications.
Method The experiments were carried out at two different temperatures: 25°C and also 60°C. Sulfuric acid, nitric acid, acetone, and distilled water were used in the process, with varying treatment times of 60, 120, 240, 360, and 420 seconds. The recovered fibers were characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR).
Result The optimum treatment time and temperature were different for all three types of fibers. Initially, the glass fiber yielded promising results at room temperature and with a minimal 120-s processing time. Carbon fiber treatment was successful at 60°C with a 420-s treatment time. However, some surface damage was observed in the Kevlar® fiber at 60°C.
Conclusion The chemical recycling process is the most sustainable, energy- and cost-efficient approach compared to all other available recycling processes. Also, it is possible to recover much cleaner fibers with the weave intact with an acid treatment and solvent-based recovery.
