Plastics (or polymers ). which usually contain light elements , and therefore have relatively low density, are generally insulators, and are flexible and formable at relatively low temperatures.是什么意思_Plastics (or polymers ). which usually contain light elements , and therefore have relatively low density, are generally insulators, and are flexible and formable at relatively low temperatures.在線(xiàn)翻譯_英語(yǔ)_讀音_用法_例句