Abstract
<jats:p>Polymer composite materials reinforced with nanoscale fillers are increasingly utilized in mechanical engineering due to their ability to replace conventional metallic components operating under friction, moisture, temperature fluctuations, and dynamic loading. Polyamide-6 (PA6) is one of the most promising polymer matrices because of its high strength, elasticity, and wear resistance. However, its practical application is limited by low hardness, thermal expansion, and dimensional instability. In this study, iron oxide (FeO) nanoparticles were introduced into the PA6 matrix to investigate their influence on the structural organization of the polymer using infrared (IR) spectroscopy. The objective was to evaluate how interactions between the aromatic and aliphatic structural fragments of PA6 and FeO nanoparticles affect supramolecular ordering and hydrogen bonding. The IR spectral analysis revealed shifts and intensity changes in the characteristic bands of Amide I, II, III, V, and VI, indicating the disruption and redistribution of hydrogen bonds and partial reorganization of the macromolecular network. The appearance of additional peaks at 823, 886, and 1503 cm⁻¹ and the merging or shifting of bands at 700 and 600 cm⁻¹ showed the formation of new interactions, including imide, immonium, and carboxylate-related structures. With an FeO content of up to 40 wt.%, significant amorphization or transition to the γ-modification was observed. The disappearance of certain C–N vibrational peaks indicated decyclization processes and molecular-level interaction between filler and polymer, accompanied by changes in hydrogen bonding patterns and electrostatic associations. The results confirm that FeO nanoparticles play a structural-regulating role in PA6 composites and can be used for targeted modification of physicochemical and tribological properties relevant to mechanical engineering applications.</jats:p>