Effects of acid treatment on the recovery of outdated resin-impregnated composite fibers

Abstract

Purpose The composites industry is constantly being formed by myriad forces—technologies, markets, people- all encouraging innovative ways to apply carbon, Kevlar®, and glass fiber composites to produce vital parts for a wide range of applications. The expanded demand for fiber-reinforced plastic (FRP) composites has prompted high manufacturing scrap and end-of-life waste volumes. Limited clearance on landfills and the high energy for virgin material production motivate the companies for practical composite recycling techniques. The work described in this study involves an array of experiments including acid treatment of outdated resin-impregnated composite fibers (prepreg) to study its effects and reclaiming the fibers for future sustainable manufacturing.

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 s. 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.