The polymer foil industry is one of the leading producers of plastic waste. The development of new recycling methods for packaging products is one of the biggest demands in today’s engineering. The subject of this research was the melt processing of multilayered PET-based foil waste with PETG copolymer. The resulting blends were intended for additive manufacturing processing using the fused deposition modeling (FDM) method. In order to improve the properties of the developed materials, the blends compounding procedure was conducted with the addition of a reactive chain extender (CE) and elastomeric copolymer used as an impact modifier (IM). The samples were manufactured using the 3D printing technique and, for comparison, using the traditional injection molding method. The obtained samples were subjected to a detailed characterization procedure, including mechanical performance evaluation, thermal analysis, and rheological measurements. This research confirms that PET-based film waste can be successfully used for the production of filament, and for most samples, the FDM printing process can be conducted without any difficulties. Unfortunately, the unmodified blends are characterized by brittleness, which makes it necessary to use an elastomer additive (IM). The presence of a semicrystalline PET phase improves the thermal resistance of the prepared blends; however, an annealing procedure is required for this purpose.

The main topic of the presented work is the evaluation of the in-line viscometer (VIS) operation installed on the industrial line for polyethylene terephthalate (PET) foil production. The tests were performed during the regular operation of the machine, which results from the need to maintain production continuity. Polymer viscosity control is of particular importance in the production of degradable materials and recycled polymers. The processing of PET film is, therefore, a particularly difficult issue due to the presence of both of these problems at the same time. The conducted research had a two-pronged character: assessment of the correct operation of the viscosity measurement system and testing of the effectiveness of reactive additives during the extrusion process. Measurements were carried out with the use of several types of input materials, including recycled blends. The key tests were carried out with the addition of viscosity modifiers. Measurements conducted during the extrusion process confirmed the effectiveness and high sensitivity of the in-line system (VIS), while clear changes in the polymer flow characteristics were observed only after the addition of chain extenders. The in-line measurements revealed that the addition of 1% of the reactive compound increased the viscosity from the initial 150 Pa∙s to over 350 Pa∙s. The most significant increase in viscosity for the additive based on pyromellitic dianhydride (PMDA) confirms the effectiveness of the reactive extrusion method and the suitability of the used measuring. During further analysis, the obtained films were also tested. The results showed no negative effects of the reactive extrusion on the mechanical performance of the foil; however, for recycled materials, the average values of tensile strength and elongation at break have deteriorated. A positive aspect of the use of reactive additives was the greater uniformity of mechanical properties. For some materials, there was a significant increase in the haze factor (transparency), which should be considered a disadvantage.

This research aimed to evaluate the material properties of reactive extrusion-modified blends containing PET multilayered foil waste. Three types of PET-based multilayer foil waste were used as the compound during the reprocessing of standard bottle-grade PET. Flakes used for this purpose were made from laminated foils: (A) PET/PE, (B) PET/EVOH/PE, and PET/PE/met. All types of the prepared materials were compounded with 30% of the waste foil flakes. Additionally, the blend was modified with an epoxy-based chain extender and polyolefin-based impact modifier. The prepared blends were processed using two methods; initially, the materials were prepared by injection molding, while cast-film samples were also prepared. All samples were subjected to full characterization using mechanical testing methods, thermal analysis, and structural observations. The study shows that the addition of multilayered foil waste is leading to significant deterioration of PET-based material properties. While, in most cases, the use of a chain extender led to some improvement in mechanical characteristics, the impact modifier addition strongly influenced most of the properties. It was also observed that the reactive extrusion procedure led to melt strength improvement, which greatly facilitates the film production process. Due to the limited possibility of separating the film components, the developed method of foil recycling might be useful for the utilization of multilayered packaging.