From Macro to Micro Plastics; Influence of Photo-oxidative Degradation

The impact of plastic waste on the environment, human health, and ecosystems is one of the most important issues today. Once released into the environment, plastic waste is exposed to various stress factors that can lead to a reduction in its structural integrity and consequently to its fragmentation into smaller pieces. In this work, the effects of simulated UV aging on the surface properties and fragmentation of high-density polyethylene (HDPE) films were studied. HDPE films were prepared from pristine polymer granules, and aged for 14, 28, and 42 days under artificial UV irradiation. The samples were characterised before and after each irradiation period to inspect structural and surface changes. FTIR spectra revealed the appearance of carbonyl (C=O) and carbon-oxygen (C−O, O−C=O, C−O−O−) groups due to photodegradation of HDPE. The change in surface polarity with UV irradiation time was determined by measuring the water contact angle, while the surface morphology was analysed using a SEM microscope. The results revealed a significant increase in carbonyl index, increased hydrophilicity, and increased brittleness resulting from a high degree of photodegradation after 28 and 42 days of UV irradiation. The different particle size distribution yielded upon grinding indicated that aged HDPE films are more prone to fragmentation into micro-sized particles.