Recycling polymer composite granulate/regrind using big area additive manufacturing

Carbon fiber filled acrylonitrile butadiene styrene (CF-ABS) is an emerging 3-D printable, recyclable thermoplastic composite. A popular application for CF-ABS is printed molds using large scale additive manufacturing (AM) processes produced for a variety of composites end-users. Other applications have not been fully realized as CF-ABS currently has a higher cost than other polymer composite feedstocks. The cost of CF-ABS could be greatly reduced if recycled CF-ABS material was accepted and utilized industrially, which would further expand its application space. The impacts of mechanical recycling on the properties and performance of CF-ABS after AM or other processes are not yet fully understood. As such, most AM CF-ABS is discarded as waste after use. In this work, AM CF-ABS molds used for concrete castings were recycled using an industrial shredder/granulator system. The granulate was then used as feedstock for large area AM to print test specimens. The elastic moduli in the printing direction and transverse to printing direction after mechanical recycling were found to decrease by 25% and 10%, respectively, most likely caused by reductions in the fiber content and polymer molecular weight. It was found that a significant portion of carbon fiber is lost during mechanical recycling through dust generation, while the thermomechanical extrusion during printing caused the polymer degradation. Although the mechanical performance of CF-ABS was reduced after recycling, the recycled feedstock retained properties for reuse as printed molds using large area AM or another suitable application.