EPR Study of the Structural Properties of Powder Coatings Under the Influence of Laser Radiation

This article presents electron paramagnetic resonance (EPR) studies of commercial polyester resin-based powder coatings before and after laser irradiation. Two industrial powder coatings were examined. The main objective was to evaluate whether localized laser irradiation leads to measurable changes in the behavior of paramagnetic centers and whether these changes are comparable to effects observed under thermal treatment. EPR spectroscopy was chosen due to its high sensitivity to unpaired electrons and paramagnetic defects in complex polymer systems. Measurements were carried out in the temperature range of 300 to 500 K for nonirradiated samples and after laser irradiation. The analysis is focused on EPR parameters, including signal intensity, linewidth, resonance field, g_eff and integrated intensity. After laser irradiation, clear and reproducible differences in the EPR spectra were observed in comparison to the nonirradiated state. Changes in signal amplitude, linewidth, and resonance field were observed, suggesting changes in the temperature-dependent behavior of signals associated with paramagnetic centers. Temperature-dependent measurements revealed different trends before and after laser exposure, indicating that localized laser treatment produces measurable effects of predominantly thermal character in polyester resin–based powder coatings. The obtained results confirm that EPR spectroscopy is a sensitive and effective tool for monitoring laser- and temperature-induced changes in powder coatings.