UV degradation of bioplastics and conventional plastics in the marine environment

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dc.contributor.advisorAkdogan, Guvenen_ZA
dc.contributor.advisorChimphango, Annie Fabian Abelen_ZA
dc.contributor.advisorDorfling, Christieen_ZA
dc.contributor.authorMzabane, Ondelaen_ZA
dc.contributor.otherStellenbosch University. Faculty of Engineering. Dept. of Process Engineering.en_ZA
dc.date.accessioned2023-03-03T12:35:37Zen_ZA
dc.date.accessioned2023-05-18T07:03:34Zen_ZA
dc.date.available2023-03-03T12:35:37Zen_ZA
dc.date.available2023-05-18T07:03:34Zen_ZA
dc.date.issued2023-03en_ZA
dc.descriptionThesis (MEng)--Stellenbosch University, 2023.en_ZA
dc.description.abstractENGLISH 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.en_ZA
dc.description.abstractAFRIKAANS OPSOMMING: In die moderne era is daar beduidende produksieverhoging van en aanvraag vir konvensionele plastiek. Verhoogde plastiekgebruik is ’n ernstige kommer vir die wêreld. Dit is as gevolg van die akkumulasie van plastiek in die oseaanomgewing, wat lei tot negatiewe impak op die oseaan se ekosisteem. In die oseaanomgewing, word plastiek blootgestel aan ultraviolet (UV) radiasie, temperatuurveranderinge, fisiese stres, southeidsgraad, en oksidasie. Daarom, ’n sleutelstrategie om hierdie kwessie te adresseer, is om aktief bioafbreekbare plastiek te bevorder en ontwikkel in ’n poging om plastiekbesoedeling te adresseer en verlig in die oseaanomgewing. Die studie het beoog om fisiese en chemiese afbreking tussen bioplastiek en konvensionele plastiek na mikro-plastiek in die oseaanomgewing te vergelyk, met min of geen mikro-organisme effekte. Drie verskillende plastiek is ondersoek: polipropileen (PP), poliëtileentereftalaat (PET), en polimelksuur (PLA). Alle plastiek was 4 cm x 10 cm in grootte. Plastiek is blootgestel aan twee behandelinge in verskillende omgewings: (i) ’n droë UVvoorbehandeling (in lug) van suiwer plastiek by twee UV-irradiansies (65 en 130 W/m2 ), en (ii) kunsmatige seewatertoetse onder dieselfde UV-kondisies. Elke lopie het vir vier weke aangehou, waar UV-radiasie tydens die lopie in ’n siklus beweeg het vir ’n totaal van 24 uur: 12 ure aan, en 12 ure af. Monstering het elke sewe dae plaasgevind vir verdere analise. Vir tekens van afbreking is veranderinge in massaverlies, karbonielindeks, persentasie kristalliniteit, hardheid en morfologie gevolg. Resultate van UV-voorbehandelingtoetse het getoon dat in lug, hoë UV-irradiansie (130 W/m2 ) meer afbreking tot gevolg gehad het in vergelyking met lae UV-irradiansie (65 W/m2 ). Polipropileen was meer vatbaar vir afbreking as poliësters (PET en PLA). Afbreking in seewater was stadig vir alle plastiek. Daar was ’n afname in meeste eienskappe van seewater in vergelyking met die voorbehandelingstoetse. Dit is omdat, in seewater, die afgebreekte oppervlakke van die voorbehandeling dalk weggespoel is, wat nuwe oppervlaktes ontbloot. Hierdie ondersoek het getoon dat die afbrekingstempo temperatuur-afhanklik is, en prosesse in die oseaan stadiger is omdat seewater ’n goeie hittesink is. Polimelksuur was die plastiek wat die minste gereageer het tot UV-afbreking in beide omgewings.en_ZA
dc.description.versionMastersen_ZA
dc.formatx, 98 pages : illustrationsen_ZA
dc.identifier.urihttp://hdl.handle.net/10019.1/127085
dc.language.isoen_ZAen_ZA
dc.language.isoen_ZAen_ZA
dc.publisherStellenbosch : Stellenbosch Universityen_ZA
dc.rights.holderStellenbosch Universityen_ZA
dc.subject.lcshPlastics—Effect of radiation onen_ZA
dc.subject.lcshUltraviolet radiation -- Environmental aspects en_ZA
dc.subject.lcshMarine ecosystem health en_ZA
dc.subject.lcshPolyethylene -- Analysisen_ZA
dc.subject.lcshEnvironmental degradationen_ZA
dc.titleUV degradation of bioplastics and conventional plastics in the marine environmenten_ZA
dc.typeThesisen_ZA
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