The main precursor to plastic is a byproduct of petroleum refining called hydrocarbon gas liquids.

塑料的前身是石油提炼的副产品，被称为液化烃气。

That causes the rubber to decompose into a mix of hydrocarbon gases which are drawn off.

这导致橡胶分解成碳氢化合物气体的混合物，这些气体被排出。