不知大家注意过没有，同是碳酸饮料，装在塑料瓶中的打开时冒出的泡沫就比装在铝制易拉罐中的开罐时冒出的泡沫多。难道是塑料瓶中的气泡也跑出来了不成？当然不是。不过这气泡确实和塑料中的成分有关系。

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 terephthalate: 聚乙烯对苯二酸盐

carbonated: 充了碳酸气的

polymer: 聚合体

unsurpassed: 非常卓越的

moisture: 湿气

dioxide: 氧化物

effervescent: 冒泡的

（英语点津 Annabel 编辑）