Following the COVID-19 pandemic, the volume of waste from film packaging materials has surged, resulting in the transformation of these materials into post-consumer recycled (PCR) plastics. However, PCR plastics are composed of immiscible polymers with different polarities, leading to issues such as phase separation, reduced surface uniformity, and decreased adhesion in coating and printing processes due to low interfacial adhesion. Surface modification plays a critical role in addressing these issues, and the use of polar Caprolactam-based additives can improve interfacial adhesion. This study investigates the effect of increasing recycling cycles on the surface properties of non-compatibilized polymer blends, comparing the surface characteristics with and without the application of Caprolactam coupling agent. Changes in wettability, resulting from an increase in hydrophilic functional groups after surface modification, were analyzed using contact angle measurements. The effects of surface uniformity and phase separation improvement were observed using optical microscopy and field emission scanning electron microscopy (FE-SEM). The increase in hydrophilicity, enhancement of interfacial adhesion, and improvement in surface uniformity of PCR plastics through the application of Caprolactam coupling agent suggest that these modifications may contribute to improved adhesion in coating and printing processes, as well as enhanced post-processing performance.
