Direct 3D Printing of Recycled PET/PP Granules by Shear Screw Extrusion

Abstract

This article introduces a one-step extrusion-based fused deposition modeling (FDM) approach for the challenging separation of polypropylene (PP) and polyethylene terephthalate (PET) during recycling. A shear screw printer (SSP) with shear elements was designed, and it was compared to a conventional single-screw printer (CSP) to investigate the differences in print stability, degradation levels, tensile performance, molecular orientation, and crystallization when preparing recycled PP and recycled PET blends. Although the retention effect of the SSP screw slightly increases the degradation of the blended rPP/rPET, the strong shear (2.6 × 104 s−1) applied near the extrusion exit improves the blending efficiency. The SSP also enhances molecular orientation, modulus of the parts, and reduces performance fluctuations. Additionally, the SSP has the potential to simplify the recycling process, enabling the transformation of blended recycled materials into products with just one melt process.

The Development of Sustainable Polyethylene Terephthalate Glycol-Based (PETG) Blends for Additive Manufacturing Processing—The Use of Multilayered Foil Waste as the Blend Component

“…The existing studies mainly related to PET and PLA recycling and include some interesting results. The topic of a few papers was related to the processing of polymer blends containing polyolefins (PP and PE), a concept that is very close to the subject of the currently described research [ 64 , 65 , 66 ]. However, it is worth noting that, unlike works devoted to research on injection molded or extruded materials, the discrepancy in the results for research in the field of 3D printing technology is very large, and covers also the reinforced materials [ 67 ].…”

“…In the case of these tests, a more detailed phase analysis would be possible, but, similarly to those discussed in this work, the authors focused on the analysis of mechanical properties. Examples of other works where polymer mixtures of the PET/polyolefin type were used during 3D printing indicate that the interpretation of results for polymer systems with undefined composition is extremely difficult and subject to a lot of assumptions [ 65 , 66 , 77 ].…”