Unveiling the degradation dynamics of packaging plastics: Insights into the onset of microplastics formation through photodegradation

The persistence of plastic packaging, combined with limited recycling and predominant disposal, accelerates its transformation into microplastics. Yet the mechanisms underlying this transition remain insufficiently understood despite rising concern over environmental and health impacts. In this study, packaging plastics (PET, PP, and HDPE) were subjected to 0 to 1000 h of simulated natural photodegradation to determine the critical onset of microplastic formation. Comprehensive characterization, including Fourier Transform Infrared Spectroscopy, Raman spectroscopy, 3D Laser Scanning Confocal Microscope, Field-Emission Scanning Electron Microscope, colorimetric analysis, and tensile testing, was employed to assess physical, chemical, optical, and mechanical changes. The results revealed that the surface morphology of PET, PP, and HDPE significantly changes after 100, 750, and 1000 h of exposure, respectively, which is supported by the carbonyl index value. The weight loss due to degradation follows a linear progression for PET (R 2 =0.9516), PP (R 2 =0.9707), and HDPE (R 2 =0.9601), providing an indicator of microplastic formation. The degradation was assessed to be thickness-dependent, with 0.3 mm films losing 50% weight within 1.43 years, indicating accelerated microplastic generation. The findings reveal key insights into the transition from plastics to microplastics, providing valuable recommendations for mitigating microplastic formation and reducing the environmental impact of packaging materials.