Characterization of Fiber Dust Resulting from Recycling of Carbon Fiber-Reinforced Thermoplastics (CFRP) and Their Cell Toxicity

Abstract

Carbon fiber-reinforced thermoplastics (CFRP) have excellent specific strength and rigidity, which has made them a popular material for lightweight construction. The growing demand for fiber-reinforced plastics (FRP) leads to the problem of the sustainable handling of FRP at the end of their life cycle. The aim of the research project was to gain knowledge about the shredding of FRP concerning the optimal machine and process design of the shredding process and the possible formation of harmful, inhalable dust fractions and WHO fibers. Toxicity should be investigated at the cellular level. The investigated shredding parameters influence the amount and length of fiber dust produced, both when shredding with a cutting mill and when shredding with a single-shaft shredder. In all investigations, an increasing rotational speed leads to an increase in the fiber dust mass or the fiber concentration. The proportion of short, respirable fibers increases, but raising the speed does not lead to a further, significant shortening of the fibers. A reduction in feedstock size leads to a slightly reduced mass of fiber dust in the ground material. A reduction in the screen size also leads to an increase in fiber dust mass and concentration. There was no recognizable cytotoxicity in the relevant concentration range up to 500 μg/cm 2 and no significant induction of cell migration. This indicates minor flammable effects of the dust formed after inhalation. The biological data indicate that the WHO fibers produced by shredding a re only a minor health hazard. Formally, the detected carbon fiber (CF ) fragments meet the fiber definition of the legislator. However, carbon fibers currently have no specific limit value.