The properties and characteristics of a particular member of the plastics family, PET (polyethylene terephthalate), causes carbonated drinks to bubble more in plastic cups. PET, a clear, strong polymer, has unsurpassed gas and moisture barrier properties. Its ability to contain carbon dioxide makes it the plastic, and the material of choice for carbonated beverage containers. PET containers have no competition in retaining carbon dioxide, the gas responsible for the effervescent, bubbling effect. The property that gives rise to a vast number of bubbles is the unique barrier layers, which prevent the loss of carbonation. The barrier layers serve to keep the container airtight, which keeps the carbon dioxide from leaking out, and oxygen from entering. This is why containers made from PET plastic keep carbonated beverages colder, more flavorful, and fizzier. polyethylene: 聚乙烯 terephthalate:對苯二酸鹽(或酯) polymer: 聚合體 unsurpassed: 非常卓越的   effervescent: 冒泡   fizzy: 泡沫沸騰