Assessment of polyurethane seal degradation in pneumatic drives using EPR and SEM techniques

• Electron Paramagnetic Resonance (EPR) was used for non-destructive monitoring of polyurethane seal degradation. • Multi-temperature EPR measurements allowed magnetic characterization using the Curie–Weiss model. • Simulated EPR spectra (EasySpin) identified contributions from Fe 3+ , carbon radicals, and metal oxides. • SEM-EDS revealed morphological degradation and correlated metallic inclusions with EPR signals. • The proposed methodology provides an effective diagnostic tool for predicting polyurethane seal lifespan. This study presents a quantitative assessment of degradation in polyurethane seals used in pneumatic actuators, based on advanced spectroscopic and microscopic measurement techniques. Electron Paramagnetic Resonance (EPR) spectroscopy was employed to identify and track paramagnetic centers, line shifts, and g-factor (g) variations across samples subjected to different operational environments and service lifespans. Scanning Electron Microscopy (SEM) complemented the spectral data by revealing microstructural surface changes and fracture patterns. Comparative analysis of new and used seals revealed significant, temperature-dependent changes in EPR spectral profiles, particularly the emergence and intensification of line D, linked to magnetic interactions. Measurement parameters such as line width (ΔB) and g-factor were systematically recorded and analyzed across multiple temperatures. These findings provide a metrologically robust framework for non-destructive condition monitoring of polymer seals. The proposed methodology demonstrates the viability of EPR and SEM as diagnostic tools for assessing the operational lifespan and failure mechanisms of elastomeric components in industrial environments. To identify the spectral components, simulations were performed using the EasySpin software for three seals at a temperature of 100 K. The EPR spectrum components were identified based on the simulated spectra. The simulations assumed contributions from potential paramagnetic centers (carbon, iron, copper, titanium, and oxides), and magnetic interactions were also considered. Based on the Curie–Weiss law, the type of magnetic interactions was determined, indicating antiferromagnetism, and the Néel temperature was estimated.