HDPE is made under controlled conditions by applying intense heat to petroleum. This process, also known as “cracking,” helps create ethylene gas. During its production, the gas molecules will attach to form polymers, which then produce polyethylene.

After this process, the polyethylene will have a sludgy appearance, but after it’s put through a series of molds, it forms into granules. Once the molding process is complete, you’ll have a strong polymer material.

High-density polyethylene. HDPE is manufactured at low temperatures and pressures, using Ziegler-Natta and metallocene catalysts or activated chromium oxide (known as a Phillips catalyst). ... The plastic recycling code number of HDPE is #2. The linear form of polyethylene, known as high-density polyethylene (HDPE).

High-densitypolyethylene(HDPE) orpolyethylene high-density(PEHD) is athermoplasticpolymerproduced from the monomerethylene. It is sometimes called "alkathene" or "polythene" when used forHDPE pipes.[1]With a high strength-to-density ratio, HDPE is used in the production ofplastic bottles, corrosion-resistant piping,geomembranesandplastic lumber. HDPE is commonly recycled, and has the number "2" as itsresin identification code.

In 2007, the global HDPE market reached a volume of more than 30 million tons.[2]