Evaluating the Thermal and Mechanical Effects of Flame Retardant Additives during Reprocessing of Acrylonitrile Butadiene Styrene (ABS) and Fused Filament Production

Abstract While flame-retardant additives are critical for improving fire safety, they often compromise the recyclability of thermoplastics. This study investigates how flame-retardants affect the recycling of acrylonitrile butadiene styrene (ABS) and its subsequent production into 3D printing filament. 2019 model ABS both with the flame-retardant additive (ABS-FR) and without (ABS) were taken from an old printer, crushed into uniform flakes, and subjected to chemical, thermal, and mechanical characterization. Although the FTIR profile of the sample were preserved, the incorporation of flame retardants markedly altered its thermal behavior. Compared to unmodified ABS (degradation onset: 350°C; T g: 107°C), ABS-FR demonstrated a lower thermal stability, with an earlier degradation onset at 325°C, alongside a modestly reduced glass transition temperature of 103°C. Material processing was significantly affected, as evidenced by the lower melt flow rate of ABS-FR (30 ± 0.1 g/10 min) compared to ABS (41 ± 0.3 g/10 min). The extruded ABS-FR filament exhibits a considerably lower diameter (1.52 ± 0.03 mm) compared to ABS (1.80 ± 0.03 mm), thereby restricting its suitability for 3D printing applications. As anticipated, the compression-molded ABS-FR plates exhibited superior flame resistance. Crucially, the incorporation of flame retardants significantly modified the mechanical behavior of the material: ABS-FR demonstrated a higher tensile modulus (2574 ± 84.12 MPa) and lower tensile strength (31 ± 0.70 MPa), reflecting enhanced stiffness and lower load-bearing capacity. These findings underscore the critical trade-offs that flame retardants impose on recycled ABS, affecting fire safety, end-of-life processing, application viability, and mechanical performance.