High-density

polyethylene Polyethylene or polythene (abbreviated PE; IUPAC name polyethene or poly(methylene)) is the most commonly produced plastic. It is a polymer, primarily used for packaging ( plastic bags, plastic films, geomembranes and containers including b ...

(HDPE) or polyethylene high-density (PEHD) is a

thermoplastic A thermoplastic, or thermosoft plastic, is any plastic polymer material that becomes pliable or moldable at a certain elevated temperature and solidifies upon cooling. Most thermoplastics have a high molecular weight. The polymer chains associate ...

polymer A polymer (; Greek '' poly-'', "many" + ''-mer'', "part") is a substance or material consisting of very large molecules called macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic a ...

produced from the monomer ethylene. It is sometimes called "alkathene" or "polythene" when used for

HDPE pipe HDPE pipe is a type of flexible plastic pipe used for fluid and gas transfer and is often used to replace ageing concrete or steel mains pipelines. Made from the thermoplastic HDPE (high-density polyethylene), its high level of impermeability and ...

s. With a high strength-to-density ratio, HDPE is used in the production of

plastic bottles A plastic bottle is a bottle constructed from high-density or low density plastic. Plastic bottles are typically used to store liquids such as water, soft drinks, motor oil, cooking oil, medicine, shampoo, milk, and ink. The size ranges from v ...

, corrosion-resistant piping, geomembranes and plastic lumber. HDPE is commonly recycled, and has the number "2" as its

resin identification code The ASTM International Resin Identification Coding System, often abbreviated RIC, is a set of symbols appearing on plastic products that identify the plastic resin out of which the product is made. It was developed in 1988 by the Society of t ...

. In 2007, the global HDPE market reached a volume of more than 30 million tons.

Properties

HDPE is known for its high strength-to-density ratio. The density of HDPE ranges from 930 to 970 kg/m³. The standard method to test plastic density is ISO 1183 part 2 (gradient columns), alternatively ISO 1183 part 1
MVS2PRO density analyzer
. Although the density of HDPE is only marginally higher than that of

low-density polyethylene Low-density polyethylene (LDPE) is a thermoplastic made from the monomer ethylene. It was the first grade of polyethylene, produced in 1933 by Imperial Chemical Industries (ICI) using a high pressure process via free radical polymerization. Its ...

, HDPE has little branching, giving it stronger

intermolecular force An intermolecular force (IMF) (or secondary force) is the force that mediates interaction between molecules, including the electromagnetic forces of attraction or repulsion which act between atoms and other types of neighbouring particles, e.g. ...

s and

tensile strength Ultimate tensile strength (UTS), often shortened to tensile strength (TS), ultimate strength, or F_\text within equations, is the maximum stress that a material can withstand while being stretched or pulled before breaking. In brittle materials t ...

(38 MPa versus 21 MPa) than LDPE. The difference in strength exceeds the difference in density, giving HDPE a higher

specific strength The specific strength is a material's (or muscle's) strength (force per unit area at failure) divided by its density. It is also known as the strength-to-weight ratio or strength/weight ratio or strength-to-mass ratio. In fiber or textile applic ...

. It is also harder and more opaque and can withstand somewhat higher

temperature Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measurement, measured with a thermometer. Thermometers are calibrated in various Conversion of units of temperature, temp ...

s (120 °C/248 °F for short periods). High-density polyethylene, unlike

polypropylene Polypropylene (PP), also known as polypropene, is a thermoplastic polymer used in a wide variety of applications. It is produced via chain-growth polymerization from the monomer propylene. Polypropylene belongs to the group of polyolefins a ...

, cannot withstand normally required

autoclaving An autoclave is a machine used to carry out industrial and scientific processes requiring elevated temperature and pressure in relation to ambient pressure and/or temperature. Autoclaves are used before surgical procedures to perform steriliza ...

conditions. The lack of branching is ensured by an appropriate choice of

catalyst Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...

(e.g.,

Ziegler–Natta catalyst A Ziegler–Natta catalyst, named after Karl Ziegler and Giulio Natta, is a catalyst used in the synthesis of polymers of 1-alkenes ( alpha-olefins). Two broad classes of Ziegler–Natta catalysts are employed, distinguished by their solubility: * ...

s) and

reaction Reaction may refer to a process or to a response to an action, event, or exposure: Physics and chemistry *Chemical reaction *Nuclear reaction * Reaction (physics), as defined by Newton's third law *Chain reaction (disambiguation). Biology and m ...

conditions. High DPE is resistant to many different

solvent A solvent (s) (from the Latin '' solvō'', "loosen, untie, solve") is a substance that dissolves a solute, resulting in a solution. A solvent is usually a liquid but can also be a solid, a gas, or a supercritical fluid. Water is a solvent for ...

s, so it cannot be glued. Pipe joints must be made by welding. 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 is the international standardized testing methods employed to identify these properties for a specific process. For example, in rotational molding, to identify the environmental stress crack resistance of a sample, the ''notched constant tensile load test'' (NCTL) is put to use. Owing to these desirable properties, pipes constructed out of HDPE are ideally applicable for

drinking water Drinking water is water that is used in drink or food preparation; potable water is water that is safe to be used as drinking water. The amount of drinking water required to maintain good health varies, and depends on physical activity level, a ...

and waste water (storm and sewage).

Applications

File:HDPE Construction safety net.jpg, HDPE fibers can be spun into rope File:Pulling on the hood of the Tyveck suit (5429334133).jpg, Disposable suits; nonwoven HDPE fabric File:US Navy 100824-N-0858D-272 Sailors work on a new home for Habitat for Humanity during Boise Navy Week.jpg,

Housewrap Housewrap (or house wrap), also known by the genericized trademark homewrap (or home wrap), generally denotes a modern synthetic material used to protect buildings. Housewrap functions as a weather-resistant barrier, preventing rain or other fo ...

File:Registered Mail Royal Mail - Great Britain-Germany 2017 - envelope front side.jpg, Plastic mailing envelopes File:Blue Striped Water Pipe.jpg, Flexible HDPE pipes File:Hdpe pipe installation.jpg, Corrugated HDPE pipe installation in storm drain project in

Mexico Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...

File:Plastic outdoor chair 1 2017-06-14.jpg, The monobloc chair File:Hanoi Vietnam The-omnipresent-plastic-chairs-01.jpg, Stools for outdoor use File:Milk crate.jpg, Bottle crates File:Cubocubo.png, Toys and playground equipment File:2014. Уничтоженные гривны в Донецке 015.jpg, Clear plastic bags (shown) are made of LDPE; blown-film shopping bags with handles are now made of HDPE File:250ml HDPE pump plastic bottle.jpg, HDPE is used to make sturdy bottles that resist oils. Transparent bottles are usually made of other plastics, such as polyethylene terephthalate File:Bottle of milk.jpg, Milk jug File:Diverse Kanisterformen.png, HDPE

jerrycan A jerrycan (also written as jerry can or jerrican) is a robust liquid container made from pressed steel (and more recently, high density polyethylene). It was designed in Germany in the 1930s for military use to hold of fuel, and saw wides ...

s resist softening and swelling from aromatic components of fuels File:FODS Connect202 TC-1 TRACKOUT CONROL STABILIZED CONSTRUCTION ENTRANCE 2.jpg, Roller on HDPE construction entrance mat HDPE has a wide variety of applications; for applications that fall within the properties of other polymers, the choice to use HDPE is usually economic: *

3D printer 3D printing or additive manufacturing is the construction of a three-dimensional object from a CAD model or a digital 3D model. It can be done in a variety of processes in which material is deposited, joined or solidified under computer co ...

filament * Arena board (puck board) * Backpacking frames * Ballistic plates * Banners * Bottle caps * Boats *

Chemical A chemical substance is a form of matter having constant chemical composition and characteristic properties. Some references add that chemical substance cannot be separated into its constituent elements by physical separation methods, i.e., w ...

containers * Chemical-resistant piping *

Coax cable Coaxial cable, or coax (pronounced ) is a type of electrical cable consisting of an inner conductor surrounded by a concentric conducting shield, with the two separated by a dielectric ( insulating material); many coaxial cables also have a p ...

inner insulator * Conduit protector for electrical or communications cables *

Corrosion Corrosion is a natural process that converts a refined metal into a more chemically stable oxide. It is the gradual deterioration of materials (usually a metal) by chemical or electrochemical reaction with their environment. Corrosion engi ...

protection for steel pipelines * Electrical and plumbing boxes * Far-IR lenses *

Fireworks Fireworks are a class of low explosive pyrotechnic devices used for aesthetic and entertainment purposes. They are most commonly used in fireworks displays (also called a fireworks show or pyrotechnics), combining a large number of devices ...

Folding chair A folding chair is a type of folding furniture, a light, portable chair that folds flat or to a smaller size, and can be stored in a stack, in a row, or on a cart. It can be combined with a folding table. Uses Folding chairs are generally used f ...

s and tables *

Food storage container Food storage containers are widespread in use throughout the world and have probably been in use since the first human civilizations. Early civilizations In early civilizations cereal grains such as maize, wheat, barley etc. were stored in large ...

s *

Fuel tank A fuel tank (also called a petrol tank or gas tank) is a safe container for flammable fluids. Though any storage tank for fuel may be so called, the term is typically applied to part of an engine system in which the fuel is stored and propelle ...

s for vehicles * Geomembrane for hydraulic applications (such as canals and bank reinforcements) * Geothermal heat transfer piping systems * Heat-resistant firework

mortars Mortar may refer to: * Mortar (weapon), an indirect-fire infantry weapon * Mortar (masonry), a material used to fill the gaps between blocks and bind them together * Mortar and pestle, a tool pair used to crush or grind * Mortar, Bihar, a villag ...

(

Tyvek Tyvek () is a brand of synthetic flashspun high-density polyethylene fibers. The name "Tyvek" is a registered trademark of the American multinational chemical company DuPont, which discovered and commercialized Tyvek in the late 1950s and early ...

) * Hovercraft: The material is too heavy and dense for such craft but is still used occasionally * Ionizing radiation shield *Laundry detergent jugs *

Last A last is a mechanical form shaped like a human foot. It is used by shoemakers and cordwainers in the manufacture and repair of shoes. Lasts typically come in pairs and have been made from various materials, including hardwoods, cast iron, an ...

s for shoes * Microwave telescope windows * Milk jugs *

Natural gas Natural gas (also called fossil gas or simply gas) is a naturally occurring mixture of gaseous hydrocarbons consisting primarily of methane in addition to various smaller amounts of other higher alkanes. Low levels of trace gases like carbo ...

distribution pipe systems * Piping for fluid, slurry and gas purposes * Plastic bags *

Plastic bottle A plastic bottle is a bottle constructed from high-density or low density plastic. Plastic bottles are typically used to store liquids such as water, soft drinks, motor oil, cooking oil, medicine, shampoo, milk, and ink. The size ranges from v ...

s suitable both for recycling or re-use *

Plastic surgery Plastic surgery is a surgical specialty involving the restoration, reconstruction or alteration of the human body. It can be divided into two main categories: reconstructive surgery and cosmetic surgery. Reconstructive surgery includes cranio ...

(skeletal and facial reconstruction) * Potable water mains * Root barrier * Shampoo bottles * Sewage mains * Snowboard rails and boxes * Stone paper * Storage sheds * Swimming pool installation * Trackout control mats * Telecom ducts * Water pipes for domestic water supply and agricultural processes * Wood plastic composites (utilizing recycled polymers) T Joint cross section

HDPE is also used for cell liners in United States subtitle D sanitary landfills, wherein large sheets of HDPE are either extrusion welded or wedge welded to form a homogeneous chemical-resistant barrier, with the intention of preventing the pollution of

soil Soil, also commonly referred to as earth or dirt Dirt is an unclean matter, especially when in contact with a person's clothes, skin, or possessions. In such cases, they are said to become dirty. Common types of dirt include: * Debri ...

and

groundwater Groundwater is the water present beneath Earth's surface in rock and soil pore spaces and in the fractures of rock formations. About 30 percent of all readily available freshwater in the world is groundwater. A unit of rock or an unconsolidated ...

by the liquid constituents of solid waste. HDPE is preferred by the pyrotechnics trade for mortars over steel or PVC tubes, being more durable and safer: HDPE tends to rip or tear in a malfunction instead of shattering and becoming shrapnel like the other materials. Milk bottles, jugs, and other hollow goods manufactured through

blow molding Blow molding (or moulding) is a manufacturing process for forming hollow plastic parts. It is also used for forming glass bottles or other hollow shapes. In general, there are three main types of blow molding: extrusion blow molding, injectio ...

are the most important application area for HDPE, accounting for one-third of worldwide production, or more than 8 million tonnes. Above all, China, where beverage bottles made from HDPE were first imported in 2005, is
growing market
for rigid HDPE packaging, as a result of its improving standard of living. In India and other highly populated, emerging nations, infrastructure expansion includes the deployment of pipes and cable insulation made from HDPE. The material has benefited from discussions about possible health and environmental problems caused by PVC and polycarbonate associated bisphenol A (BPA), as well as its advantages over glass, metal, and cardboard.

References

{{DEFAULTSORT:High-Density Polyethylene Plastics Polyolefins de:Polyethylen

Properties

Applications

See also

References