Browsing by Author "Mzabane, Ondela"

Now showing 1 - 1 of 1
  • Thumbnail Image
    Item
    UV degradation of bioplastics and conventional plastics in the marine environment
    (Stellenbosch : Stellenbosch University, 2023-03) Mzabane, Ondela; Akdogan, Guven; Chimphango, Annie Fabian Abel; Dorfling, Christie; Stellenbosch University. Faculty of Engineering. Dept. of Process Engineering.
    ENGLISH ABSTRACT:In the modern era, there has been a significant increase in the production of and demand for conventional plastics. Increased plastic use is a serious concern for the world. This is because of the accumulation of plastic in the marine environment, which leads to negative impacts on the marine ecosystem. In the marine environment, plastics are exposed to ultraviolet (UV) radiation, temperature changes, physical stress, salinity, and oxidation. Therefore, a key strategy to address this issue is to actively promote and develop biodegradable plastics in efforts to address and alleviate plastic pollution in the marine environment. The study aimed to investigate and compare physical and chemical degradation between bioplastics and conventional plastics to micro-plastics in the marine environment, with little or no microorganism effects. Three different plastics were investigated: polypropylene (PP), polyethylene terephthalate (PET), and polylactic acid (PLA). All plastics were 4 cm × 10 cm in size. Plastics were exposed to two treatments in different environments: (i) a dry UV pretreatment (in air) of neat plastics at two UV irradiances (65 and 130 W/m2 ), and (ii) artificial seawater tests under the same UV conditions. Each run commenced for four weeks, during which UV radiation was cycled for a total of 24 hours: 12 hours on, and 12 hours off. Sampling took place every seven days for further analysis. For signs of degradation, changes in mass loss, carbonyl index, percentage crystallinity, hardness, and morphology were tracked. Results from UV pre-treatment tests showed that in air, high UV irradiation (130 W/m2 ) resulted in more degradation compared to low UV irradiation (65 W/m2 ). Polypropylene was more susceptible to degradation than polyesters (PET and PLA). Degradation in seawater was slow for all plastics. There was a decrease in most properties of seawater compared to the pretreatment tests. This is because, in seawater, the degraded surfaces from the pre-treatment may have been washed away, exposing new surfaces. This investigation showed that the degradation rate is temperature-dependent, and processes in the ocean are slowed down because seawater is a good heat sink. Polylactic acid was the least responsive plastic to UV degradation in both environments.