Investigation of closed-loop manufacturing with acrylonitrile butadiene styrene over multiple generations using additive manufacturing

This study examines the changes in physical and mechanical properties of acrylonitrile butadiene styrene (ABS) when manufactured using fused filament fabrication (FFF) 3D printing across multiple recycling phases. Tests were carried out initially using virgin ABS, which subsequently underwent two successive closed-loop filament extrusion and 3D printing phases. For each endpoint manufacturing phase, samples were examined to monitor the changes in thermal characteristics, mechanical properties, and polymer degradation. It was found that there was a series of physical changes of the polymer, which resulted in reduced melt flow, increased glass transition temperature, and the generation of carbonyl groups, which may be attributed to the thermal oxidative breakdown of both styrene acrylonitrile (SAN) and butadiene components of ABS. The recycled polymer also showed a reduction in both tensile and compressive strengths compared to the virgin material. However, compared to one-time recycled ABS, two-times recycled ABS showed increased strength, implying that increased recycle state of the polymer may be advantageous with respect to mechanical properties and potential manufacturing applications. This study ultimately demonstrates the potential to leverage additive manufacturing (AM) toward a closed-loop manufacturing paradigm by using waste ABS across several life cycles.