High density polyethylene

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High density polyethylene (HDPE) is a polyethylene thermoplastic made from petroleum. It takes 1.75 kilograms of petroleum (in terms of energy and raw materials) to make one kilogram of HDPE.

Properties

HDPE has little branching, giving it stronger intermolecular forces and tensile strength than lower density polyethylene. It is also harder and more opaque and can withstand somewhat higher temperatures (120 °C for short periods, 110 °C continuously). High-density polyethylene, unlike polypropylene, cannot withstand normally required autoclaving conditions. The lack of branching is ensured by an appropriate choice of catalyst (e.g. Ziegler-Natta catalysts) and reaction conditions.

Applications

HDPE is resistant to many different solvents and has a wide variety of applications, including:

• Containers
  • Tupperware
  • Laundry detergent bottles
  • Milk cartons
• Plastic bags
• Containment of certain chemicals
• Chemical-resistant piping systems
• Geothermal heat transfer piping systems

HDPE is also used for cell liners in subtitle D sanitary landfills, wherein large sheets of HDPE are either extrusion or wedge welded to form a homogeneous chemical-resistant barrier, preventing the pollution of soil and groundwater by the liquid constituents of solid waste.

HDPE has one of its largest use for Wood Plastic Composites, with recycled polymers leading the way.

See also

• Resin identification code