This paper presents the obtaining and characterization of recycled polypropylene/strontium ferrite (PP/SrFe₁₂O₁₉) polymer composite materials with applications in the electromagnetic shielding of vehicle interiors (mainly automotive electronics—carcasses) from the electromagnetic radiation emitted mainly by exterior sources—electrical lines and supply sources—in terms of the development of the new electrical vehicles. With this aim, suitable polymer composite materials were developed using SrFe₁₂O₁₉ filler in two forms (powder and concentrate). The recycled PP polymer and composite materials with a PP/SrFe₁₂O₁₉ weight ratio of 75/25 and 70/30 were obtained in two stages, i.e., pellets by extrusion and samples for testing through a melt injection process. The characterization of the obtained materials took into account the requirements imposed by the desired applications. It consisted of determining the mechanical and dielectric properties, and microstructure analyses, along with the determination of the resistance to the action of a temperature of 70 °C, which is higher than the temperatures created during the summer inside vehicles. The performance of these materials as electromagnetic shields was assessed through functional tests consisting of the determination of magnetic permeability and the estimation of the electromagnetic shielding efficiency (SE). The obtained results confirmed the improvement of the mechanical, dielectric, and magnetic properties of the PP/SrFe₁₂O₁₉ composites compared to the selected PP polymers. It is also found that all the composite materials exhibited reflective shielding properties (SE_R from −71.5 dB to −56.7 dB), with very little absorption shielding. The most performant material was the composite made of PP/SrFe₁₂O₁₉ powder with a weight ratio of 70/30. The promising results recommend this composite material for potential use in automotive shielding applications against electromagnetic pollution.

This paper describes the process used to produce thermoplastic building materials from non-recyclable mixed plastic–paper packaging waste. A first step was dedicated to an innovative and sustainable sterilization technology for non-recyclable waste, based on exposure to microwave radiation in closed air-circulation ovens. Further, composites with different cellulose contents and with two polymer matrices, respectively, were obtained using an injection process, and the samples were subjected to mechanical and physical tests. Due to their superior features, the products based on mixed polypropylene–paper packaging waste may successfully replace the classic polyvinylchloride-based wood–plastic composites. The environmental impact of mixed plastic–paper packaging waste was analyzed, and the sustainability of the thermoplastic technology was demonstrated from an economic and environmental point of view.

The European methodology for plastics, as a feature of the EU’s circular economy activity plan, ought to support the decrease in plastic waste. The improvement of recycled plastics’ economics and quality is one important part of this action plan. Additionally, achieving the requirement that all plastic packaging sold in the EU by 2030 be recyclable or reusable is an important objective. This means that food packaging materials should be recycled in a closed loop at the end. One of the most significant engineering polymers is polyethylene terephthalate (PET), which is widely used. Due to its numerous crucial qualities, it has a wide variety of applications, from packaging to fibers. The thermoplastic polyolefin, primarily polyethylene and polypropylene (PP), is a popular choice utilized globally in a wide range of applications. In the first phase of the current experiment, the materials were obtained by hot pressing with the press machine. The reinforcer is made of Al nanopowder 800 nm and Fe nanopowder 790 nm and the quality of the recycled polymer was examined using Fourier transform infrared spectroscopy (FTIR), a scanning electron microscope (SEM), and differential scanning calorimetry (DSC). From DSC variation curves as a function of temperature, the values from the transformation processes (glass transition, crystallization, and melting) are obtained. SEM measurements revealed that the polymer composites with Al have smooth spherical particles while the ones with Fe have bigger rough spherical particles.

In the present study, dielectric spectroscopy was used to assess the influence of ELF (1-200 Hz) electromagnetic fields over protein relaxation from activated sludge (approx. 99% water content), sampled from the biological tank of a domestic wastewater treatment plant. Dielectric loss (tgδ) was determined for both activated sludge samples and autoclaved samples. Experimental data analysis shows that biological samples (activated sludge) have different dielectric behavior than the sterile samples (sterilized sludge). Unlike sterile samples in which the function tgδ vs. frequency is continuous, in the activated sludge samples, this function presents two discontinuities specific to electrical resonances around the frequencies of 26.5 Hz and 50.1 Hz. This behavior indicates that under the influence of the measuring signal of 26.5 Hz and 50.1 Hz, biochemical processes are stimulated in activated sludge. Also, the significant changes in the number of charge carriers suggest that, at these frequencies, changes occur in the mechanism and kinetics of biochemical processes.

Steel surface protection with hard coatings is essential in metalworking, yet developing high-performance coatings is challenging. TiAlSiN coatings grown on various substrates using commercial targets have been extensively studied, but consistent data on their properties are lacking. This study focused on TiAlSiN single layers (SL) and TiAlSiN/TiN bilayers (BL), with an 800 nm thick TiAlSiN top layer and a 100 nm thick TiN mid layer. These coatings were grown on C120 tool steel discs via reactive DC magnetron sputtering using TiAlSi 75–20–5 at.% and Ti targets fabricated in-house through spark plasma sintering. The stability of coatings was assessed after thermal treatment (TT) in air at 800 °C for 1 h. SEM analysis revealed a columnar microstructure with pyramidal grains in the SL and BL coatings, and coarser pyramidal and prismatic grains in both TT coatings. EDS analysis showed a decrease in Ti, Al, Si, and N content after annealing, while O content increased due to oxide formation. High indentation hardness (9.19 ± 0.09 GPa) and low effective elastic modulus (148 ± 6 GPa) were displayed by the BL TT coating, indicating good resistance to plastic deformation and better load distribution. The highest fracture toughness was noted in the BL TT coating (0.0354 GPa), which was 16.4 times greater than the steel substrate. Better scratch resistance and low coefficient of friction (COF ≤ 0.35) were exhibited by both TT coatings. Tribological tests showed a mean COF of 0.616–0.773, comparable to the steel substrate (0.670). The lowest corrosion current density (0.1298 µA/cm²), highest polarization resistance (46.34 kΩ cm²), and a reduced corrosion rate (1.51 µm/year) in a 3.5 wt.% NaCl solution was also exhibited by the BL TT coating. These findings indicate TiAlSiN/TiN films as effective protective coatings for tool steel surfaces.

The behavior of two polymeric protective paint coatings (epoxy and polyurethane) applied over an epoxy primer coating on steel plates was investigated in this study, focusing on their role in providing anticorrosive protection against various climatic stress factors. Among the numerous climatic factors that can affect the lifetime of anticorrosive coatings, the following were selected for this work: dry heat, UV radiation, humidity, and extreme conditions such as salt fog, marine atmosphere, and alpine atmosphere. The objective was to determine the remaining lifetime of these protective coatings before replacement is needed to prevent damage to the equipment they protect. The behavior of these polymeric materials under the mentioned factors was analyzed based on the variation in the tangent of the dielectric loss angle (tg δ) with frequency. From the interpretation of the experimental results, it was found that the polyurethane paint coating (P2) exhibits superior resistance to climatic degradation compared to the epoxy paint coating (P1). Furthermore, a comparison of tg δ values for the P1 and P2 coatings revealed that the initial (unaged) P2 coating performs better as an insulator (dielectric) than the P1 coating. Comprehensive information is provided to the users of polymeric anticorrosive protection materials, highlighting the extent to which climatic factors can affect the performance of the equipment they protect and determining the appropriate timing for replacing the coatings.