My shampoo bottles are made of HDPE, but I don't know much about it!

Category (2) High-Density Polyethylene (HDPE)

What is HDPE?

High-Density Polyethylene (HDPE) is a type of plastic with a higher specific density than Low-Density Polyethylene (LDPE). It is commonly referred to as Plastic #2 in plastic categories. HDPE differs in its physical properties by being lightweight yet having high tensile strength. Its molecular structure is compact, making HDPE a linear polymer.

How is  HDPE produced?

The production of HDPE begins with applying intense heat to petroleum, a process known as "fracking", which helps create ethylene gas. During the process, the gas molecules combine to form polymers that produce polyethylene, which is then shaped into granules through various stages. Once the forming process is complete, a strong polymer material is obtained, which can be used in a variety of products and applications that surround us.

History of HDPE

The grade of HDPE used today is different from the materials of earlier generations. In the late 1800s, German chemist Hans von Pechmann observed a precipitate while working with a form of methane in ether. In 1900, German chemists Eugen Bamberger and Friedrich Tschirner identified this substance as POLYMETYLEN, a material closely related to polyethylene. Thirty years later, a high-density residue was created by an American chemist at E.I. du Pont de Nemours & Company, Inc., Carl Shipp Marvel, subjecting ethylene to high pressure.

Working with ethylene at high pressures, British chemists Eric Fawcett and Reginald Gibson created a strong form of polyethylene in 1935. Its first commercial application came during World War II when the British used it to insulate radar cables. In 1953, Karl Ziegler of the Kaiser Wilhelm Institute (later renamed the Max Planck Institute) and Erhard Holzkamp invented high-density polyethylene (HDPE). Two years later, in 1955, HDPE was produced as a tube. Ziegler was honored with the Nobel Prize in Chemistry in 1963 for his successful invention of HDPE.

  • In 1963 Karl Ziegler was honored with the Nobel Prize in Chemistry for inventing HDPE;
  • HDPE releases a high amount of air pollution during production (sulfur oxides, particulates, nitrogen oxides, carbon monoxide, non-methane hydrocarbons, and carbon dioxide);
  • Only 12% of all HDPE plastic bags and 28% of milk jugs and containers are recycled;
  • If 1 out of 10 HDPE plastic bottles were recycled, 90 million kg of plastic would be saved from landfills;
  • 160,000 plastic bags are discarded every second, totalling four million each year.

Why is HDPE widely used?

  • It has a higher density than other grades of PE;
  • It is a semi-crystalline polymer;
  • It is lightweight and robust;
  • It is flexible;
  • HDPE is recyclable;
  • It is resistant to moisture;
  • It has high chemical resistance.