3D printing has grown rapidly and is now widely used in many industries, including the automotive sector. Most 3D printing filaments are made from virgin PLA (polylactic acid); however, at the same time, the packaging industry produces large amounts of PLA waste, which is often not recycled properly. Turning this waste into good-quality 3D printing filament could be an eco-friendly alternative to traditional materials and support sustainability in the automotive supply chain. This research investigates whether the original PLA packaging material can be used for 3D printing at all by testing its printability and mechanical properties compared to commercial PLA filaments. Two types of original packaging PLA were chosen and processed into 3D printing filaments, which were then tested. The results show that packaging PLA filaments have mechanical properties similar to or even better than commercial PLA filaments, proving that they can be a useful material for 3D printing.

The present paper focuses on the effect of carbon nanotubes (CNTs) on the rheological behavior of polyethylene/polypropylene (PE/PP) blends to improve PE/PP mixtures for industrial applications. In our research, 40 wt% HDPE-60 wt% PP blends were produced by extrusion, and 0.59%, 1.18%, and 2.35% multiwalled carbon nanotubes (MWCNTs) were added. Oscillation rheometry was used to study the HDPE-PP-MWCNT nanocomposites and the unfilled polymers at temperatures of 210, 220, 230, 240, and 250 °C in the angular frequency range of 0.05–628.32 rad/s, with 5% deformation. It was demonstrated that in the presence of CNTs, both the complex viscosity and modulus values increase above the percolation threshold. Additionally, it was observed that the crossover modulus (Gx) for all mixtures decreases with increasing temperature. In addition, at 1.18% CNT content, a second crossover appears at all temperatures, and its value increases with temperature.