Degradation and Fragmentation of Microplastics

The degradation of plastics in the ocean environment is especially interesting because it is believed to be the primary mechanism leading to fragmentation that generates secondary microplastics from plastic macro-litter. Degradation processes are generally classified according to the primary causative agent. Natural weathering of plastics on land environments is quite a slow process even under harsh exposure conditions of a sandy beach. This chapter reviews the chemistry of photo-oxidation of common polymers found in the ocean environment, especially those that float in seawater. The ocean environment consists of several zones that are very different in their ability to promote natural weathering of plastic litter. The first paper on photo-degradation of plastics in seawater was presented in the United States at a symposium held by the Society of Plastics Industry in 1987 and included preliminary data on the photodegradable polyethylenes.