Study and characterization of recycled ABS-GF in large format additive manufacturing to enhance mechanical properties of printed structures

Large format additive manufacturing (LFAM) has proven its ability to produce high-performance components for competitive markets. By depositing material only where it's needed, it drastically reduces waste material and energy use, obtaining a sustainability advantage that is further enhanced on larger scale. However, a deeper understanding of material recycling is critical to achieving the next milestone in sustainability. In this work, a methodology was proposed that uses both molds and final parts, manufactured in acrylonitrile-butadiene-styrene reinforced with short glass fibers (ABS-GF), which had reached the end of their useful life to be used as feedstock. It is observed that recycling reduces fiber length by 47.3%, which directly impacts the mechanical properties in the longitudinal printing direction, resulting in around a 9% decrease in maximum tensile stress. However, this reduction falls to 5.1% in the transverse direction to the printing, and in some cases, the recycled material even surpasses the virgin material due to improved interlayer adhesion. An analysis on the adhesion reveals that the shorter monomer chains obtained during recycling allow better interlacing between layers. These results suggest that the reuse of the molds is viable and by adjusting the printing parameters we can obtain properties suitable for demanding applications.