Recycled carbon fibers and their possible applications by reinforcing PA66/6I in combination with a flame retardant additive

The use of carbon fibers is increasing worldwide, leading to the need for recycling of those materials. From a fiber matrix separation point of view there are already existing technologies available for the reclamation of recycled carbon fibers (rCF). On the other hand, there are not many existing industrial applications where recycled carbon fibers are used. The aim of this study is to investigate the mechanical properties of reinforced polyamide and thermoset matrix systems and their behavior at different temperatures and the influence of an industrial forming process in case of thermoplastic matrix systems to then identify possible applications for the material. Overall, this study investigates the use of a novel PA66/6I polymer supplied by Asahi Kasei Corporation as a matrix material with rCF from cutoff waste and a flame-retardant additive. The PA66/6I composites are compared with PA66 and epoxy composites, each reinforced with rCF in the form of a dry-laid nonwoven, through bending tests at different temperatures ranging from -30°C to 150°C. Also, the influence on the mechanical properties of an organic aluminum phosphinate based flame retardant (FR) was investigated. In addition, the processing of organic sheets made with the thermoplastic polymers is studied and the impregnation quality of isothermal molded parts is shown. It was found that the PA66/6I matrix results in similar mechanical properties compared to highly used PA66 or epoxy matrix materials but offers advantageous wetting and impregnation behavior during production of the CFRPs, resulting in more homogeneous CFRP parts and faster part production, which is very important for the use in e.g. automotive applications. The presentation was held at JISSE-19, Ariake Central Tower Hall & Conference, Tokyo, Japan on Dec. 2, 2025, Panel 1B-01, Room "Reception 1".