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Impact of hydrolytic degradation on mechanical properties of PET - Towards an understanding of microplastics formation
Summary
Scientists studied how PET plastic (used in water bottles) breaks down when exposed to hot water over time, discovering that the plastic becomes brittle and cracks apart once its molecular chains get cut short enough, and once that happens, it takes very little force to shatter into tiny pieces. This research helps explain how large plastic waste in oceans breaks down into microplastics, which is a key step toward predicting and eventually reducing the tiny plastic particles that end up in our water, food, and bodies.
Ocean pollution by microplastics , i.e. small pieces of plastic of less than 5 mm, is one of the major concerns for the future of our planet. Secondary microplastics formation is due to fragmentation of macroplastic waste. This fragmentation can be attributed to environmental loadings such as waves, winds and tides, coupled with a change in mechanical properties of polymers induced by UV and seawater ageing. This study aims to characterize and understand changes in the mechanical behaviour of Polyethylene Terephthalate (PET) induced by hydrolysis, especially for high degradation levels. Thin films (200 μm) of PET were aged in water at temperatures from 110 °C to 80 °C for up to 150 days. Embrittlement occurs with chain scission during hydrolysis when molar mass of the polymer falls below 17 kg/mol. When the polymer is brittle, i.e. for high levels of degradation, the stress at break decreases linearly with the molar mass , and can be described by a simple mathematical expression.