The major chemical elements making up petroleum are oxygen (O), hydrogen (H), and carbon(C)."

Petroleum is decomposed under heat into gasoline, kerosene, naphtha, light oil, heavy oil, etc. Most plastics use naphtha as main raw material. Naphtha is further decomposed thermally and separated utilizing the difference in the boiling point (temperature at which the phase change from liquid to gas occurs) to form ethylene and propylene, which are the raw materials for plastics. However, many of these gases and liquids are not ready for use as they are.

About "mono" and "poly"

To produce a high-molecular compound, it is necessary to first produce low-molecular compounds and bond them together. This reaction is known as polymerization, the low-molecular compounds as " monomers," and the high-molecular-weight substance as a " high-molecular compound" or "polymer." The word "mono" means "single" while "poly" means "multiple." The formation of polymers from monomers uses heat, light, and additives such as enzymes (polymerization initiators). In this way, ethylene and propylene, which are monomers, are polymerized into polyethylene and polypropylene.