Morphology and chemical properties of polypropylene pellets degraded in simulated terrestrial and marine environments

• Published in: Marine pollution bulletin Vol. 149; no. C; p. 110626
• Main Authors: Tang, Chih-Cheng, Chen, Huey-Ing, Brimblecombe, Peter, Lee, Chon-Lin
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01-12-2019; Elsevier BV; Elsevier
• Subjects: Analytical methods; Biocides; Biofilms; Carbonyl compounds; Carbonyls; Chemical analysis; Chemical properties; Chemicophysical properties; Cracks; Darkness; Electron microscopy; Environmental changes; Environmental conditions; Environmental degradation; Hydroxyl groups; Infrared spectroscopy; Irradiation; Marine debris; Marine environment; Morphology; Organic chemistry; Oxidation; Pellets; Photo degradation; Photodegradation; Polypropylene; Scanning electron microscopy; Seawater; Solar radiation; Surface cracking; Terrestrial environments; Thermal degradation; Ultraviolet radiation; Water analysis; Surface cracking; Photo degradation; Environmental degradation; Marine debris; Thermal degradation
• ISSN: 0025-326X; 1879-3363
• DOI: 10.1016/j.marpolbul.2019.110626

Polypropylene (PP) pellets exposed to solar radiation, ultraviolet B (UVB) radiation and heat in four stimulated treatments: dry-air, seawater-air, seawater-darkness, and dry-darkness for 0.5–1.5 years to investigate morphology and chemical change under various environmental conditions. Scanning electron microscopy and infrared spectroscopy were employed to characterize the virgin and degraded pellets. The degraded PP pellets under solar and UVB irradiation revealed 35% and 12% cracks, respectively. Moreover, carbonyl and hydroxyl groups formed on the surface gradually extended to the interior. However, under photo-irradiation, PP pellets floating in seawater showed less degradation than those in a dry environment. The formation of biofilm may retard the photo-degradation of PP pellets in the seawater when biocides are absent. Results also indicated that the photo oxidation dominated over thermal oxidation during the degradation process in the terrestrial and marine environments.
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•Dry polypropylene exposed to solar and UVB radiation degraded as cracked surfaces.•In seawater the formation of biofilm slows polypropylene photodegradation.•Biological activity in seawater led to fibrous structures on the plastic.•Photo-oxidation dominated thermal oxidation in the production of CO and OH groups.
The morphology and chemical properties of polypropylene pellets degraded in the terrestrial and marine environments reveal their interaction between marine pollutant and biota and help us understand the fate of plastic debris.