不知大家注意過沒有，同是碳酸飲料，裝在塑料瓶中的打開時冒出的泡沫就比裝在鋁制易拉罐中的開罐時冒出的泡沫多。難道是塑料瓶中的氣泡也跑出來了不成？當然不是。不過這氣泡確實和塑料中的成分有關系。

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: 聚乙烯對苯二酸鹽

carbonated: 充了碳酸氣的

polymer: 聚合體

unsurpassed: 非常卓越的

moisture: 濕氣

dioxide: 氧化物

effervescent: 冒泡的

（英語點津 Annabel 編輯）