High density polythene (HDPE) is a thermoplastic polymer derived from petroleum. The material is used in a variety of applications where the plastic has to undergo tougher stresses and strains. Along with boxes, bottles and plastic frames, HDPE has certain mechanical properties that make it suitable for various piping applications for natural gas and geothermal heat.
HDPE can withstand temperatures up to 49 degrees C (120F) and as low as -73 degrees C (-100F). This makes it the ideal material mechanically for transporting hot and cold substances as well as geothermal heat and pressurised liquids. Its melting point is at 130 degrees C (260F). This is also useful in manufacturing as the material can be shaped and moulded at relatively low temperatures.
HDPE has a higher density than standard polythene, with a rating of around 0.950 grams per cubic cm (59.3 lb per cubic feet). This means its atomic structure is much more closely packed than other substances with a lower rating, allowing HDPE to withstand higher pressures without breaking.
Tensile strength refers to how much pressure a piece of material can withstand before breaking or ripping into two parts. The tensile strength of HDPE is commonly around 241 bar (3,500 Psi). This also makes it ideal for transporting high-pressure substances and means it can be easily manufactured into shapes without the risk of damage to the material's structure.
HDPE has a hardness rating of SD65, with the SD standing for standard deviation. Due to its high density, HDPE is very rigid and hard so it will not deform. The hardness rating on its own is not a particularly impressive value, but combined with its tensile strength and density allows the physical structure of HDPE to remain strong when being manufactured for specific applications and during usage.