Recipe Development and Mechanical Characterization of Carbon Fibre Reinforced Recycled Polypropylene 3D Printing Filament

Abstract

Recycled polypropylene filaments for fused filament fabrication were investigated with and without 14 wt% short fibre carbon reinforcements. The microstructure and mechanical properties of the filaments and 3D printed specimens were characterized using scanning electron microscopy and standard tensile testing. It was observed that recycled polypropylene filaments with 14 wt% short carbon fibre reinforcement contained pores that were dispersed throughout the microstructure of the filament. A two-stage filament extrusion process was observed to improve the spatial distribution of carbon fibre reinforcement but did not reduce the pores. Recycled polypropylene filaments without reinforcement extruded at high screw speeds above 20 rpm contained a centreline cavity but no spatially distributed pores. However, this cavity is eliminated when extrusion is carried out at screw speeds below 20 rpm. For 3D printed specimens, interlayer cavities were observed larger for specimens printed from 14 wt% carbon fibre reinforced recycled polypropylene than those printed from unreinforced filaments. The values of tensile strength for the filaments were 21.82 MPa and 24.22 MPa, which reduced to 19.72 MPa and 22.70 MPa, respectively, for 3D printed samples using the filaments. Likewise, the young's modulus of the filaments was 1208.6 MPa and 1412.7 MPa, which reduced to 961.5 MPa and 1352.3 MPa, respectively, for the 3D printed samples. The percentage elongation at failure for the recycled polypropylene filament was 9.83% but reduced to 3.84% for the samples printed with 14 wt% carbon fiber reinforced polypropylene filaments whose elongation to failure was 6.58%. The SEM observations on the fractured tensile test samples showed interlayer gaps between the printed and the adjacent raster layers. These gaps accounted for the reduction in the mechanical prop-How to cite this paper:

FDM-based additive manufacturing of recycled thermoplastics and associated composites

“…However, 3D printed specimen from the same filament showed reduced tensile strength from 21.82 and 24.22 MPa to 19.72 and 22.70 MPa, respectively. The reduction was due to inter-layer porosity and the anisotropic mechanical behavior of 3D printed products at different raster angles, i.e., 0° and 90° [ 79 ]. Interlayer cavities and porosity can be seen through SEM images of fractured 3D printed tensile specimens, as shown in Fig.…”

“…Interlayer cavities and porosity can be seen through SEM images of fractured 3D printed tensile specimens, as shown in Fig. 12 [ 79 ].

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Fig. 12 SEM images of the fractured surface of 3D printed tensile specimens a and b CF/r-PP filament; c and d formation of inter-layer gaps, porosity, fiber pullout and its alignment along the print direction [ 79 ]

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“…TS of filament increased by 10.99% 2. TS of 3D printed specimen decreased by 6.27% [ 79 ] 23. R-PET Biochar (size below 100 µm) Filabot extruder 1.75 ± 0.03 Hyrel30M 51.87 (PET/0.5 wt% Biochar) 2.…”

Evaluation of the Viability of 3D Printing in Recycling Polymers

“…Evidence from Maines et al [ 79 ] and Pricop et al [ 78 ] is consistent with evidence from Mikula et al [ 16 ] that rapid prototyping has allowed for the creation of 3D printed models designed with CAD technologies. According to findings by Polline et al [ 100 ], rapid prototyping allows for the creation of objects of different models and sizes with the utilization of cheap 3D printing feedstock from recycled plastics. The findings consistently show that 3D printing is a reliable method of recycling plastics, given the availability of supporting technologies, such as HME, FDM, and rapid prototyping.…”