High-density polyethylene

  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.

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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 jugs
  • Fuel tanks for vehicles
• Plastic bags
• Containment of certain chemicals
• Chemical-resistant piping systems
• Heat-resistant fireworks display mortars
• Geothermal heat transfer piping systems
• Natural gas distribution pipe systems
• Water pipes, for domestic water supply.
• Coax cable inner insulators (dielectric insulating spacer)
• Root Barrier
• Corrosion Protection for Steel Pipelines.
• Snowboard rails/ boxes.
• Bottles, suitable for use as refillable bottles.
• enabled manufacture of the modern hula hoop

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, with the intention of preventing the pollution of soil and groundwater by the liquid constituents of solid waste.

One of the largest uses for HDPE is wood plastic composites, with recycled polymers leading the way.

HDPE is also widely used in the fireworks community. In tubes of varying length (depending on the size of the ordnance), HDPE is used as a replacement for the supplied cardboard mortar tubes for two primary reasons: One, it is much safer than the supplied cardboard tubes because, if a shell were to malfunction and explode inside (flower pot) an HDPE tube, the tube will not shatter. Two, they are reusable allowing designers to create multiple shot mortar racks. Pyrotechnicians discourage the use of PVC tubing in mortar tubes because it tends to shatter, sending shards of plastic at possible spectators, and will not show up in x-rays.

See also

• Linear low-density polyethylene
• Low-density polyethylene
• Resin identification code
• Ultra-high-molecular-weight polyethylene