可降解共混塑料在海水中的光降解研究

Degradable plastic blends have been widely used due to their low cost. However，it is the necessary to investigate the formation of microplastics by the photodegradation of degradable plastic blends in seawater. Three investigated microplastic materials included polyethylene/calcium carbonate blends （PE/CaCO₃） and polyethylene/thermoplastic starch blends （PE/TPS），and polyethylene （PE） were prepared by mechanical grinding in this study. The photodegradation of microplastics in natural seawater under solar irradiation was investigated. The results show that degradable plastic blends are more likely to generate small-sized particles than PE under the same weathering conditions. More debris and particles are present on the surface of the aged degradable plastic blends than in the aged PE after irradiation. There are no significant changes in the ATR-FTIR and C1s XPS spectra of PE after irradiation. An oxygen-containing functional group （C—O） is appeared in PE/CaCO₃ due to the photooxidation. For PE/TPS，the intensity of the TPS absorption peaks decreased significantly after irradiation，indicating the depletion of the starch fraction. Combined with changes in contact angle and surface potential for the three types of microplastics，aging degradable plastic blends may have a greater adsorption capacity than PE for hydrophilic contaminants. In summary，degradable plastic blends have a higher degree of photodegradation than PE in the marine environment，and may pose a higher risk to the marine environment，thus caution should be taken in promoting plastic blends.