Ultra high molecular weight polyethylene (UHMWPE), also known as high modulus polyethylene (HMPE) or high performance polyethylene (HPPE), is a thermoplastic made from oil. It has extremely long chains, with molecular weight numbering in the millions, usually between 3.1 and 5.67 million. The high molecular weight results a very good packing of the chains into the crystal structure. This results in a very tough material, with the highest impact strength of any thermoplastic presently made. It is highly resistant to corrosive chemicals, with exception of oxidizing acids. It has extremely low moisture absorption, very low coefficient of friction, is self lubricating and is highly resistant to abrasion. Its coefficient of friction is significantly better than nylon and acetal, and is comparable to teflon, but UHMWPE has also better abrasion resistance than teflon. It is odorless, tasteless, and nontoxic. Polyethylene or polyethene is an engineering thermoplastic heavily used in consumer products. ... A thermoplastic is a plastic that softens when heated and hardens again when cooled. ... Nodding donkey pumping an oil well near Sarnia, Ontario, 2001 Petroleum (from Latin petra – rock and oleum – oil), crude oil, sometimes colloquially called black gold, is a thick, dark brown or greenish flammable liquid, which exists in the upper strata of some areas of the Earths crust. ... The molecular mass of a substance (less accurately called molecular weight and abbreviated as MW) is the mass of one molecule of that substance, relative to the unified atomic mass unit u (equal to 1/12 the mass of one atom of carbon-12). ... Rose des Sables (Sand Rose), a formation of gypse crystal In mineralogy and crystallography, a crystal structure is a unique arrangement of atoms in a crystal. ... In dermatology, an abrasion is superficial damage to the skin, generally not deeper than the epidermis. ... This article covers the material nylon. ... Polyoxymethylene, also known as polytrioxane and polyformaldehyde. ... Teflon is the brand name of a polymer compound discovered by Roy J. Plunkett (1910-1994) of DuPont in 1938 and introduced as a commercial product in 1946. ...

UHMWPE finds use in high modulus fibers (for example, Spectra or Dyneema) for bulletproof vests. Due to its low friction and wear resistance it is used in industrial impact, wear, and sliding applications in both normal and corrosive environment. It is also used in orthopaedic implants (artificial hips, knees). In solid mechanics, Youngs modulus (also known as the modulus of elasticity or elastic modulus) is a measure of the stiffness of a given material. ... Dyneema or Spectra is a synthetic fibre, 15 times stronger than steel, three times stronger than Kevlar. ... A bullet resistant vest – also called body armour (U.S. body armor) – is an article of protective clothing that works as a form of armour to minimize injury from being hit by a fired bullet. ... Orthopedic surgery or orthopedics (BE: orthopaedics) is the branch of surgery concerned with acute, chronic, traumatic and recurrent injuries and other disorders of the locomotor system, its musclular and bone parts. ... The term implant has different meanings: in Scientology, see Implant (Scientology) in medicine, see prosthesis This is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ... Hip replacement is the most successful, cheapest and safest form of replacement surgery. ...

Structure and properties

Structure of UHMWPE, with n greater than 100,000

UHMWPE is a type of olefin and, despite relatively weak Van der Waals bonds between its molecules, derives ample strength from the length of each individual molecule. It is made up of extremely long chains of polyethylene, which all align in the same direction. Each chain is bonded to the others with so many Van der Waals bonds that the whole can support great tensile loads. Wikipedia does not have an article with this exact name. ... Wikipedia does not have an article with this exact name. ... An olefin is an alkene hydrocarbon. ... The information provided here is not complete and/or correct. ... Polyethylene or polyethene is an engineering thermoplastic heavily used in consumer products. ... Tensile stress (or tension) is the stress state leading to expansion (volume and/or length of a material tends to increase). ...

When formed to fibers, the polymer chains can attain a parallel orientation greater than 95% and a level of crystallinity of up to 85%. In contrast, Kevlar derives its strength from strong bonding between relatively short molecules. Kevlar, also known as Twaron and poly-paraphenelyne terephthalamide, is a synthetic fibre that is five times stronger than steel, weight for weight. ...

The weak bonding between olefin molecules allows local thermal excitations to disrupt the crystalline order of a given chain piece-by-piece, giving it much poorer heat resistance than other high-strength fibers. Its melting point is around 144 or 152 degrees Celsius, and according to DSM, it is not advisable to use UHMWPE fibers at temperatures exceeding 80 to 100°C for long periods of time. It becomes brittle at temperatures below -150°C. The melting point of a solid is the temperature at which it changes state from solid to liquid. ... The degree Celsius (°C) is a unit of temperature named after the Swedish astronomer Anders Celsius (1701–1744), who first proposed a similar system in 1742. ... For other uses of Brittle, see Brittle (disambiguation). ...

The simple structure of the molecule also gives rise to surface and chemical properties that are rare in high-performance polymers. For example, the polar groups in most polymers easily bond to water. Because olefins have no such groups, UHMWPE does not absorb water readily, but it also does not get wet easily, which makes bonding it to other polymers difficult. For the same reasons, skin does not interact with it strongly, making the UHMWPE fiber surface feel slippery. Similarly, aromatic polymers are often susceptible to aromatic solvents due to phenyl stacking, an effect aliphatic polymers like Dyneema are also immune to. Since Dyneema does not contain chemical groups (such as esters, amides or hydroxylic groups) that are susceptible to attack from aggressive agents, it is very resistant to water, moisture, most chemicals, UV radiation, and micro-organisms. ... Wetting is important in getting two different materials to adhere (stick) to each other. ... In chemistry, an aromatic molecule is one in which electrons are free to cycle around circular arrangements of atoms, which are alternately singly and doubly bonded to one another. ... Phenyl stacking is a phenomenon in organic chemistry that affects aromatic compounds. ... In chemistry, non-aromatic organic compounds are called aliphatic. ... Esters are a type of molecule usually encountered as sweet smelling organic compounds commonly produced by many plants and fruits. ... In chemistry, the term amide has several meanings. ...

Under tensile load, UHMWPE will deform continually as long as the stress is present - an effect called creep.

Production

UHMWPE is synthesized from monomers of ethylene, which are bonded together to form what is called ultra high molecular weight polyethylene (or UHMWPE). These are molecules of polyethylene which are several orders of magnitude longer than familiar, high density polyethylene due to an advanced synthesis process based on metallocene catalysts. HDPE molecules generally have between 700 and 1,800 monomer units per molecule, while UHMWPE molecules tend to have 100,000 to 250,000 monomers each. The material is also known as high modulus polyethylene (HMPE) or high performance polyethylene (HPPE). The polymers are aligned randomly when they are produced. To make fibers like Dyneema, they are dissolved and drawn into fibers as the solvent evaporates, causing the polymer chains to orient in the direction of the fiber. Synthesis (from the Greek words syn = plus and thesis = position) is commonly understood to be an integration of two or more pre-existing elements which results in a new creation. ... In chemistry, a monomer (from Greek mono one and meros part) is a small molecule that may become chemically bonded to other monomers to form a polymer. ... Ethylene or ethene is the simplest alkene hydrocarbon, consisting of two carbon atoms and four hydrogens. ... Polyethylene or polyethene is an engineering thermoplastic heavily used in consumer products. ... An order of magnitude is the class of scale or magnitude of any amount, where each class contains values of a fixed ratio to the class preceding it. ... High density polyethylene (HDPE) is a plastic made from oil. ... In chemistry, and in particular, in organometallic chemistry, a metallocene is a compound consisting of an aromatic organic ligand bound to a metal. ... A Kaminsky catalyst is a catalytic system for olefin polymerization discovered by Walter Kaminsky and coworkers in 1980. ... Dyneema or Spectra is a synthetic fibre, 15 times stronger than steel, three times stronger than Kevlar. ...

The production of UHMWPE demands relatively little energy and uses no aggressive chemicals. The product can easily be recycled, so environmental pollution from product and process is minimal.

See also

• Linear low density polyethylene
• Low density polyethylene
• High density polyethylene
• Dyneema