Polypropylene (PP) exhibits high flammability (LOI ≈ 17.5%), which limits its industrial applications. Previous studies have primarily focused on the flame-retardant mechanisms of intumescent flame-retardant (IFR) systems, while less attention has been given to the role of inorganic synergistic additives in balancing flame retardancy with mechanical performance—an aspect crucial for commercial applications This study investigated the effect of small additions of zinc oxide (ZnO) and manganese oxide (MnO) on the flame-retardant, mechanical, and thermal properties of PP/IFR (APP + PER) composites. The oxide content was varied between 0 and 2 wt.%. LOI and UL-94 tests showed that as little as 0.25 wt.% increased LOI to 30% and enabled all materials to achieve a UL-94 V-0 classification. The highest performance was observed for ZnO (LOI = 43.7% at 1.5 wt.%), while MnO induced a linear increase up to 38.6% at 2 wt.%. SEM analysis confirmed the formation of a compact, foamed char layer. Mechanical testing revealed improved stiffness (~15%) and flexural strength (~20%), with unchanged tensile strength but reduced impact strength (−50% for ZnO, −30% for MnO). The HDT increased from 55 °C to 65 °C. These findings demonstrate that small amounts of ZnO and MnO act as effective and economically viable IFR synergists in PP composites.

This study investigates the effects of destructive climatic factors on the mechanical and performance properties of various structural materials, encompassing both polymers and metals. Over recent decades, the growing adoption of synthetic polymers has revolutionized engineering applications, yet their susceptibility to environmental degradation poses significant challenges. This research emphasizes the need for comprehensive testing under both operational and environmental stressors, including extreme temperatures, UV radiation, and moisture, to assess material durability and performance. Mechanical tests were conducted at ambient (25 °C) and low temperatures (−50 °C) to evaluate the strength and strain responses of selected materials. Additionally, a 12-month accelerated aging process using UV radiation and elevated temperatures was performed to simulate long-term environmental exposure. Parameters such as Shore D hardness, gloss, and mass were measured at regular intervals to quantify material degradation. The results revealed significant differences in performance across material types. Among polymers, laser-extruded and milky plexiglass, as well as solid polycarbonate, exhibited satisfactory resistance to aging, with minimal changes in mechanical properties. However, high-impact polystyrene displayed substantial deformation and hardness loss after prolonged UV exposure. For metals, aluminum and stainless steel (304 and 316) demonstrated exceptional durability, retaining structural and aesthetic properties after 12 months of accelerated aging, whereas galvanized steel exhibited pronounced corrosion. The study highlights the critical interplay between mechanical loading and environmental factors, stressing the importance of material selection tailored to specific climatic conditions. It further underscores the value of integrating experimental findings with predictive models, such as finite element analysis, to enhance the design and longevity of engineering materials. The findings provide actionable insights for industries operating in temperate climates, where materials are subjected to diverse and cyclic environmental stressors. Recommendations are offered for selecting resilient materials suitable for protective housings and structural components.

An analysis was made of methods of chemical surface treatment of metal elements made of DC04 steel and Al6061 alloy, for the formation of polymer–metal joints in injection molding technology. The surface characterization included determination of surface free energy (SFE) by the OWRK (Owens–Wendt–Rabel–Kaelble) method, and determination of its polar and dispersive components. Depending on the chemical treatment applied, the highest values of the polar constant for DC04 and Al6061 sheets were 26.4 and 39.2 mJ/m2, respectively, the highest values of the dispersion constant were 55.6 and 53.5 mJ/m2, respectively, for DC04 and Al6061 sheets. In the case of the surfaces of sheets made of the Al6061 alloy, the increase in the polar component value was most favorably influenced by the etching with 15% NaOH solution for 5 minutes, and the increase in the dispersive component – by the etching with 15% NaOH solution with the addition of thiourea for 2 minutes. In the case of the surface of DC04 sheets, the increase of the polar component was most favorably influenced by chemical cleaning for 10 minutes (in a solution with the composition: Na2CO3 50 g/mol, Na3PO4 × 12 H2O 50 g/mol, NaOH 50 g/mol). The highest value of the dispersive component of the surface DC04 sheets was obtained after etching with 15% HCl solution with the addition of thiourea for 5 minutes.

For improving heat transfer in the thermal energy storage system (TES), cast aluminum cellular structures were designed, optimized, and produced by investment casting. The pattern was 3D printed from polylactide (PLA) polymer and then subjected to molding and heat treatment. Selected casting parameters, i.e. temperature of the mold and poured metal, as well as low pressure (vacuum), allowed to production of a complex, thin-walled casting. To evaluate the effectiveness of the structures (enhancers), a lab-scale heat accumulator was constructed and filled with phase change material (PCM) composed of KNO3 and NaNO3 salts. Thermal cycling, including charging and discharging of the accumulator, was analyzed and compared between systems with pure PCM bed and the one equipped with the produced enhancer. To protect aluminum casting against corrosion with molten salts, nickel plating was applied. Process parameters, such as plating process time and nickel subcoating application time, were determined. Microscopic observations confirmed high-quality, continuous coating on aluminum casting surfaces with characteristic microgrooves remaining after the printed pattern.