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Laboratory-Simulated Photoirradiation Reveals Strong Resistance of Primary Macroplastics to Weathering
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Researchers exposed five common plastic types to simulated UV radiation equivalent to 25–75 years of sunlight and found that while surface layers became highly oxidized and eroded, the bulk polymer remained largely intact, highlighting the strong resistance of industrial macroplastics to weathering and the resulting persistence of plastic pollution.
The photodegradation of macroplastics in the marine environment remains poorly understood. Here, we investigated the weathering of commercially available plastics (tabs 1.3 × 4.4 × 0.16 cm), including high-density polyethylene, low-density polyethylene, polypropylene, polystyrene, and polycarbonate, in seawater under laboratory-simulated ultraviolet A radiation for 3-9 months, equivalent to 25-75 years of natural sunlight exposure without considering other confounding factors. After the exposure, the physical integrity and thermal stability of the tabs remained relatively intact, suggesting that the bulk polymer chains were not severely altered despite strong irradiation, likely due to their low specific surface area. In contrast, the surface layer (∼1 μm) of the tabs was highly oxidized and eroded after 9 months of accelerated weathering. Several antioxidant additives were identified in the plastics through low temperature pyrolysis coupled with gas chromatography/mass spectrometry (Pyr-GC/MS) analysis. The Pyr-GC/MS results also revealed many new oxygen-containing compounds formed during photodegradation, and these compounds indicated the dominance of chain scission reactions during weathering. These findings highlight the strong resistance of industrial macroplastics to weathering, emphasizing the need for a broader range of plastics with varying properties and sizes to accurately estimate plastic degradation in the marine environment.
More Papers Like This
Laboratory-Simulated Photoirradiation Reveals Strong Resistance of Primary Macroplastics to Weathering
AI summary Read the abstract
Laboratory weathering experiments showed that common plastic items (HDPE, LDPE, PP, PS, PC) retain their bulk structural integrity even after simulated UV and mechanical exposure equivalent to decades of coastal conditions, yet shed a thin surface layer rich in microplastic fragments. This means macroplastics in the ocean act as a persistent, long-term source of microplastic particles even when they appear physically intact.
Experimental weathering of microplastic under simulated environmental conditions - Method development and characterization of pristine, photodegraded and mechanically weathered microplastic
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Polyethylene and polystyrene microplastics of two sizes were weathered under simulated ocean surface and intertidal conditions for 80 days to study physical and chemical degradation. Photodegradation was found to cause significant surface oxidation and embrittlement, with smaller particles and intertidal exposure conditions producing faster weathering.
Short-term degradability of plastic in the marine environment
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Researchers incubated seven common plastic polymers (PET, HDPE, PVC, LDPE, PP, PS, and EPS) in the marine environment for 40 days at two sites and two seasons, characterizing degradation through visual inspection, mass change, contact angle, FTIR, and SEM analysis. No significant mass loss occurred, but significant changes in oxidation status were recorded with an oscillating trend, and EPS showed the greatest chemical alteration, with macro-biofouling settlement appearing to shield plastics from photochemical degradation.
Influence of thermooxidative degradation on the in situ fate of polyethylene in temperate coastal waters.
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Polyethylene films were artificially aged to four levels of thermooxidative degradation, then deployed in seawater cages off the Swedish coast for 12 weeks to track in-situ degradation and fragmentation. The study found that pre-weathering significantly accelerated further deterioration in the marine environment, with implications for how plastic debris breaks down into microplastics.
Critical Impactof Colored Pigments on the Long-TermPhotoaging of Polyethylene Microplastics in Coastal Seawater Environments
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This study examined the long-term photoaging of polyethylene microplastics in coastal seawater, finding that pigment color significantly influences UV-driven surface oxidation rates and the release of additive chemicals, with darker pigments generally accelerating weathering processes.
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