## 3 Results and Discussion  
### Mechanical Properties of Films  
The test assumed a strain rate of 100 mm/min and a gage length of Lo = 50 mm. The resulting results were described by arithmetic means, standard deviation, and coefficient of variation (Table 1). For the tested recycled film (RF), the average relative elongation at which the tested film failed was 418.30%, whereas, for the film without the addition of recycled material, it was 655.06% in the longitudinal direction. Recycled film has a significantly lower tensile strength. For the RF film, the tensile strength was significantly lower than that of the film without the addition of recycled materials, as it was 21 MPa in the longitudinal direction and 21.73 MPa in the transverse direction. Tearing strength tests were conducted in accordance with the Polish standard PN-EN ISO 6383-2:2005 at room temperature. In the machine direction, the recycled film had a tear strength of 1.36 N in the longitudinal direction and 8.47 N in the transverse direction. In contrast, the polyethylene film had 0.7 N and 10.79 N, respectively (Figure 3). Impact resistance tests of the tested samples: A value of 0.7 N was obtained for films without the addition of recycled material, and a value of 0.61 N was obtained for films with the addition of recycled material (Figure 4). While conducting the test, it was noted that all samples in the series were characterized by similar damage features. The free shrinkage of the tested film samples was also compared. As part of the test, an experiment was carried out according to the conditions described in ASTM D2732. The research results are presented in Figure 5. In the longitudinal direction, the RF film had the highest shrinkage among the tested films (69%), and in the transversal direction, the NRF film (23.6%). DSC measurement: The thermal properties of the analyzed films were determined using a Mettler-Toledo apparatus based on standard ISO 11357-3:199 in the temperature range from 30 \({}^{\circ}\)C to 180 \({}^{\circ}\)C. Samples of the analyzed films were heated under the same conditions throughout the experiment. The experiment yielded values for the melting temperature, crystallization temperature, and degree of crystallinity of the film samples, which are shown in Figures 6 and 7. Figure 3: Tearing strength test results. Figure 4: Impact resistance test results. Figure 5: Shrinkage of tested film. Figure 6: DSC curve for the RF film. The glass transition of polymers is closely related to their chemical structure. Thermal DSC analysis was performed in the heating/cooling/heating process to obtain a complete description structure of the tested films. In the graph obtained for the recycled film samples (Figure 6), two peaks for the melting temperature are noticeable. Analyzing the curves for the RF film, the first peak at 109.76 \({}^{\circ}\)C and the second peak at 124.84 \({}^{\circ}\)C for heating one are noticeable, respectively. For the crystallization phase, there was one peak at 113.27 \({}^{\circ}\)C, and for heating two peaks occurred at slightly higher temperatures, i.e., 111.08 \({}^{\circ}\)C and 125.33 \({}^{\circ}\)C. For the NRF polyethylene film (Figure 6), in each of the stages of temperature changes, it is noticeable that there was a single peak in the first heating stage at 126.99 \({}^{\circ}\)C, and in the second heating stage at 128.23 \({}^{\circ}\)C. For the crystallization stage, it was 115.21 \({}^{\circ}\)C. The results obtained in the form of different values of melting temperatures for the tested film samples indicate the differences occurring in their thermal properties (Table 2). The recycled film began to melt at a much lower temperature than the non-recycled film, which is also important in the process of mass packaging of bottles at the time of sealing the film, where a lower temperature in the heating furnace is required for the recycled film.