High-density polyethylene (HDPE) is a polyethylene thermoplastic made from petroleum and HDPE is abbreviation of “High-Density Polyethylene”. In order to get a 1 kg of HDPE, approximately 1.75 kg of petroleum is used.
Manufacturing process: There are several methods for HDPE manufacturing. Polyethylene can be produced through radical polymerization, but this route typically requires high-pressure apparatus.
For the coordination polymerization metal chlorides or metal oxides are used for catalysts synthesis with lower pressures and at 50-75 degree temperatures. These catalysts consist of titanium tetrachloride and aluminium- alkyl. Polymerization temperature is removed by cooling methods. The manufactured polymer product is either in the form of powder or granule.
DPE is known for its large strength-to-density ratio. The density of HDPE can range from 0.93 to 0.97 g/cm3 or 970 kg/m3. Although the density of HDPE is only marginally higher than that of low-density polyethylene, HDPE has little branching, giving it stronger intermolecular forces and tensile strength than LDPE. The difference in strength exceeds the difference in density, giving HDPE a higher specific strength. It is also harder and more opaque and can withstand somewhat higher temperatures (120 °C/ 248 °F for short periods). High-density polyethylene, unlike polypropylene, cannot withstand normally required autoclaving conditions. The lack of branching is ensured by an appropriate choice of catalyst and reaction conditions.
The physical properties of HDPE can vary depending on the molding process that is used to manufacture a specific sample; to some degree a determining factor are the international standardized testing methods employed to identify these properties for a specific process.
HDPE is resistant to many different solvents and has a wide variety of applications such as ballistic plates, banners, bottle caps, chemical-resistant piping, food storage containers, fuel tanks for vehicles, corrosion protection for steel pipelines, geomembrane for hydraulic applications (such as canals and bank reinforcements) and chemical containment, geothermal heat transfer piping systems, water pipes and wood plastic composites.