High-Density PolyEthylene(HDPE)

High-Density PolyEthylene(HDPE) or PolyEthylene High-Density (PEHD) 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. HDPE is commonly recycled, and has the number "2" as its recycling symbol.

Polyethylene pipes both High Density (HDPE) and Medium Density (MDPE) can carry potable water, wastewater, slurries, chemicals, hazardous wastes, cables and compressed gases as well as oils. Polyethylene pipes have a long and successful service experience to the gas oil, mining and water utility industries. PE pipes have the lowest repair frequency per Kilometer of pipe per year compared with all other pipe materials used for urban water and gas distribution.

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/ 248 °F for short periods, 110 °C /230 °F 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. HDPE contains the chemical elements carbon and hydrogen.

Applications

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

• Containers
• Laundry detergent bottles
• Milk jugs
• Fuel tanks for vehicles
• Folding tables
• Folding chairs
• Storage sheds
• Portable basketball system bases
• 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
• Tyvek
• Snowboard rails and boxes
• Bottles, suitable for use as refillable bottles
• Modern hula hoops
• Ballistic plates

· 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 and composite wood, with recycled polymers leading the way.

· HDPE is also widely used in the pyrotechnics trade. HDPE mortars are preferred to steel or PVC tubes because they are more durable and more importantly they are much safer compared to steel or PVC. If a shell or salute were to malfunction (flowerpot) in the mortar, HDPE tends to rip and tear instead of shattering into sharp pieces which can kill or maim onlookers. PVC and steel are particularly prone to this and their use is avoided where possible.