By Laurie Brenner
Updated Mar 24, 2022

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TL;DR (Too Long; Didn’t Read)

HDPE (high‑density polyethylene) is a subtype of polyethylene that is denser, stronger, and more rigid—making it ideal for bottle caps, milk jugs, and water‑pipe applications. The base polymer, polyethylene (PE), is the world’s most produced plastic and forms a wide array of products from shampoo bottles to grocery bags.

Polyethylene (PE)

Polyethylene is a thermoplastic polymer derived from ethylene gas. It is the foundation for numerous plastics and is valued for its versatility, low cost, and ease of processing. Although solid polyethylene is harmless, its liquid form can pose health risks if inhaled or absorbed through the skin. LDPE (low‑density polyethylene) is the lightweight, flexible variant commonly found in grocery bags and plastic wrap.

Melting temperatures vary by density: LDPE melts at about 230 °F (110 °C), while HDPE melts at approximately 266 °F (135 °C). PE is slightly more expensive to produce than polypropylene and is the second‑most popular material for living hinges—flexible joints that maintain a consistent angle between two rigid components.

Types of Polyethylene

• HDPE – High‑Density Polyethylene
• LDPE – Low‑Density Polyethylene
• LLDPE – Linear Low‑Density Polyethylene
• UHMW – Ultra‑High Molecular Weight Polyethylene
• MDPE – Medium‑Density Polyethylene
• HMWPE – High‑Molecular‑Weight Polyethylene
• ULMWPE / PE‑WAX – Ultra‑Low‑Molecular‑Weight Polyethylene
• HDXLPE – High‑Density Cross‑Linked Polyethylene
• CPE – Chlorinated Polyethylene
• PEX / XLPE – Cross‑Linked Polyethylene
• VLDPE – Very‑Low‑Density Polyethylene

Common Uses of Polyethylene

Polyethylene’s versatility is evident in everyday items: LDPE forms the stretchable film used to cover leftovers, while PEX (cross‑linked polyethylene) serves as the plumbing backbone in modern homes, delivering water to fixtures and heating/cooling systems. UHMW variants provide the backbone for bullet‑proof vests and various medical devices.

HDPE Plastics

HDPE is a rigid, high‑impact plastic that naturally resists cracks and boasts a high melting point. Its neutral, milk‑white appearance makes it suitable for food and chemical containers—milk jugs, motor oil cans, shampoo bottles, soap dispensers, and bleach containers are all commonly fabricated from HDPE.

Because HDPE contains no BPA, phthalates, heavy metals, or other allergens, it is considered safe for beverage and food contact. HDPE is also fully recyclable: recycling 8 to 10 milk jugs can produce a single pound of new HDPE material, and more than 115 million jugs are recycled annually worldwide.