Local thermal conditions influencing the mechanical properties of recycled polypropylene as a filament for fused filament fabrication

Abstract

The utilization of recycled waste plastics presents a promising opportunity for the development of filament for fused filament fabrication (FFF). This approach holds the potential to effectively conserve resources, mitigate solid waste generation, and contribute to the reduction of greenhouse gas emissions. The present study involves the processing of recycled polypropylene (rPP) into filaments with the purpose of manufacturing 3D printed components and the effects of the processing parameters on the properties of the printed parts. The selection of manufacturing parameters for 3D printing of rPP relies on the material-specific characteristic values, including glass transition temperature, melting temperature, viscosity, etc. More importantly, a novel methodology with the self-diffusion coefficient by applying the real-time cooling rate of rPP was devised to determine the total accumulated diffusion, which enables the prediction of mechanical performance by considering the local thermal conditions during material bonding between individual strands and different layers. The finding of the study indicates that the specimen fabricated by using elevated temperature and minimal time interval, which correlates with a high total accumulated diffusion, exhibited enhanced mechanical properties between the strands those are comparable to properties of the injection-molded virgin polypropylene. • Effects of the processing parameters on the performance of filament fabricated rPP were studied. • Novel methodology of the self-diffusion coefficient was applied for exploring the mechanical performance of printed rPP. • The mechanical performance increased with increasing the total accumulated diffusion. • rPP performs on par with injection-molding level.