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.

微塑料（即小于5毫米的小塑料片）对海洋的污染是我们星球未来的主要关注之一。次生塑料的形成是由于大塑料废料的碎片化所致。这种碎裂可归因于诸如波浪，风和潮汐之类的环境负荷，以及由于紫外线和海水老化引起的聚合物机械性能的变化。这项研究旨在表征和理解水解引起的聚对苯二甲酸乙二酯（PET）机械性能的变化，特别是对于高降解水平。将PET薄膜（200μm）在水中于110°C至80°C的温度下老化150天。当聚合物的摩尔质量低于17kg / mol时，在水解过程中发生断链而脆化。当聚合物变脆时，即