In 2018, the European Commission adopted the European Strategy for Plastics in a Circular Economy, which outlines key actions to reduce the negative impact of plastic pollution. The strategy aims to expand plastic recycling capacity and increase the proportion of recycled materials in plastic products and packaging. Using recycled plastic can save 50–60% energy compared to virgin plastic. Recycled PET can be used in the production of A-PET films, which are predominantly used in thermo-vacuum forming for food packaging. Storage conditions can influence the mechanical properties of polymer materials. This work presents changes in the mechanical properties of A-PET films after UV irradiation. An experimental investigation of the UV aging of A-PET films was conducted in a UV aging chamber. The specimens were exposed to a UV radiation dose rate of 2.45 W/m² for 1, 2, 4, 8, 16, 24, 32, and 40 h. UV measurements were also taken on a sunny day to compare the acceleration of UV irradiation in the UV aging chamber. Mechanical tensile tests were performed on two different three-layer A-PET films (100% virgin and 50% recycled). The tensile strength and relative elongation of the A-PET films were determined, and the work required to break the film was calculated. The total consumed work was divided into the work needed for elastic and plastic deformations. A study of the UV aging of A-PET films confirmed a significant effect on the films, including a loss of plasticity even after brief exposure to solar irradiance. The results of the puncture impact test further confirmed the deterioration of the mechanical properties of A-PET material due to exposure to UV radiation, with a greater effect observed for the recycled material.

The use of polymer materials in various fields has increased significantly due to their ease of thermoforming and relatively low production costs. The production volume of these materials is extremely high, and according to forecasts from global statistical centers, it is expected to continue rising in the future. However, the extensive use and easy availability of polymeric materials have caused significant ecological problems. The world faces large amounts of polymer waste and environmental pollution. Plastic recycling remains challenging due to issues related to sorting polymer waste and separating it according to polymer types. Recycling certain plastics requires only a quarter of the energy needed to produce new plastic. To address this, circular economy principles should be applied to 3D printing products made from polymeric materials. A particularly wide application of these technologies is found when polymeric materials are used due to their low cost, low melting temperatures, and other advantageous properties. This paper investigates the impact of plastic recycling on the quality of 3D-printed products. During the research, samples were 3D printed and tested using both virgin and recycled PLA, ABS, and PET-G materials. The samples underwent static and dynamic tests to determine their mechanical properties, such as tensile strength, elongation, and impact resistance. The research results showed that the properties of recycled polymer materials deteriorate, with relative elongation of recycled and 3D-printed materials decreased by 16–45%. Despite this, recycled polymer materials can still be used, but it is necessary to account for the reduction in plasticity when creating products that will be exposed to dynamic loads. The impact strength is reduced by 6% for PLA, 54% for ABS, and 58% for PET-G. Additionally, the research included tests on samples printed with 3D printing technology that were exposed to UV irradiation. The results indicated similar dependences, as UV exposure also affects the reduction of material plasticity. After 66 Wh/m² of UV radiation, the tensile strength of PET-G and PLA decreased by 17%, while ABS showed a reduction of about 5%.

This paper investigates pouch-type lithium-ion battery cells with a nominal voltage of 3.7 V and a nominal capacity of 57 Ah. A numerical model of the cell was developed and implemented using the NTGK method, which accurately predicts electrochemical and thermal processes. The results of numerical modeling matched with the experimental results of battery cell temperature measurements—the average deviation was about 4.5%; therefore, it can be considered reliable for further engineering research and construction of battery modules. In the experimental part of the paper, the battery cell was loaded in various C-rates (from 0.5 to 2 C), using heat flux sensors, thermocouples, and a thermal imaging camera. The studies revealed that the highest temperature is in the tabs area of cells. The temperature on the face of the cell surface exceeds 35 °C already from a load of 1.35 C, which accelerates cell degradation and reduces the number of cycles. Thermal imaging revealed uneven temperature distribution, whereby the top of the cell heats up more than the bottom of the cell and the temperature gradient can reach 2–4 °C. It was observed that during faster charge/discharge modes, the temperature rises from the tabs of the cell, and during slower ones, more in the middle face surface of the cell. The studies highlight the need to apply additional cooling solutions, especially cooling of the upper cell face, to ensure durability and uniform heat distribution.