## 3 Results and Discussion
### The Properties of the Manufactured Foil  
The results of the mechanical tests are shown in Figure 4, where the charts present the values of the tensile strength (Figure 4A) and elongation at break (Figure 4B). The results include measurements performed in the machine direction (MD) and transverse direction (TD). In addition to samples prepared as part of the conducted experiment, the results also include measurements for reference materials, where APET (amorphous polyethylene terephthalate) refers to monolayer PET film, while PET/PE was prepared with an additional laminated polyethylene (PE) layer. Further, Figure 4C shows the results of haze factor measurements and the appearance of foil samples. The preliminary comparison shows no correlation between the results of rheological and mechanical measurements; the increased viscosity of VD-M1 and V-M1 materials does not translate into changes in the strength or elongation of foil samples. APET monolayer foil can be treated as the basic reference material. The APET film strength of 45 MPa was obtained for only two materials prepared during the conducted tests, V and VD-M1 foil. However, it is difficult to draw any more profound conclusions from this fact because the comparative analysis does not indicate any clear trends resulting from using the modifiers (M1/B1) or a different type of PET charge. Some indicators of worse properties may be low strength values for samples based on a mixture of PET flakes and preforms (MIX), but the results of elongation measurements do not confirm this. As an example of a certain tendency, the properties of the film based on the VD (dried virgin PET) material can be considered, whereas, for the VD-M1 material, a visible increase in tensile strength by about 20% and elongation by about 15% can be observed. It is worth mentioning that for this group of materials (VD) the test results in both measured directions MD and TD are very similar, which in the case of other materials is not a rule. An example of that is the results for undried materials (V), where the strength for the MD direction for samples V and V-M1 is similar (about 40 MPa), while for the same pair in the TD direction, the values are strongly different, 54 MPa and 39 MPa, respectively, for V and V-M1. In this case, the measurements indicate the adverse effect of chain extenders on tensile strength, but the analysis of the elongation at break shows completely different conclusions. For the V sample, some attention should be paid to the significant difference in elongation for the unmodified sample, where the MD direction was 585% and for the TD only 9%. After the addition of the modifiers, the differences for the MD and TD directions became negligible, additionally, the average elongation was improved. For the sample V-B1 up to 780% and for V-M1 even 880%. The analysis of the results for the mixture of preforms and flakes (MIX) shows no visible trends, which is not surprising to some extent because as a product processed from the waste form of PET, this material is assumed to be significant. The results of tensile strength measurements for this group of samples show slightly lower values than for VD and V-type foils, while elongation measurements suggest relatively good material properties because the results for all measurements were within the range of 600 to 850%. Taking into account the ambiguous changes in the properties of the PET film after the addition of chain extenders, it is worth noting that the positive aspect of using the reactive extrusion technique is the improvement of the uniformity of mechanical properties for the tested MD and TD directions. In the case of the discussed products, the level of film orientation was low; however, for the technology of producing BOPET (bi-oriented PET) films, this issue may be a key aspect of the reactive compounds application. Analyzing haze measurements (see Figure 4C) brings unexpected results.