Optical characterization analysis of surface modified-plastics (SMP) induced by atmospheric cold plasma system

Surface modification of polymers is essential for improving adhesion, coating performance, and wettability in various industrial and environmental applications. In this study, uniformly cut samples of common plastics such as polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), polyethylene terephthalate (PET), and high-density polyethylene (HDPE) were exposed to a low-cost atmospheric cold plasma (ACP) system using a zero-voltage switching (ZVS). The plasma system operated at an output of 10–20 kV, using argon (Ar), nitrogen (N₂), and oxygen (O₂) as working gases under atmospheric conditions. Samples were treated for 5 and 10 min of exposure. Surface modifications were analyzed using scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM-EDX), atomic force microscopy (AFM), Fourier-transform infrared spectroscopy (FTIR), and contact angle measurements (CAM). A pronounced roughness enhancement was found in PP and HDPE. Moderate changes were seen in PET and PVC, while PS had a minimal response. FTIR confirmed the creation of oxygen-containing functional groups (–OH, C= O), enhancing surface polarity. The contact angle of PP decreased from 108° to 47°, while HDPE decreased from 80° to 62°, showing that improvements in wettability arise from the combined effects of chemical functionalization and increased surface roughness. These findings demonstrate that the low-cost ACP system effectively tailors polymer surface chemistry and morphology, providing a scalable and eco-friendly approach for adhesion, coating, and sustainable polymer processing applications.