Ultra-high-molecular-weight polyethylene (UHMWPE, UHMW) is a subset of the
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 ...
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 bo ...
. Also known as high-modulus polyethylene, (HMPE), it has extremely long chains, with a
molecular mass
The molecular mass (''m'') is the mass of a given molecule: it is measured in daltons (Da or u). Different molecules of the same compound may have different molecular masses because they contain different isotopes of an element. The related quanti ...
usually between 3.5 and 7.5 million
amu.
The longer chain serves to transfer load more effectively to the polymer backbone by strengthening intermolecular interactions. This results in a very
tough material, with the highest
impact strength
In materials science and metallurgy, toughness is the ability of a material to absorb energy and plastically deform without fracturing.[high-density polyethylene
High-density polyethylene (HDPE) or polyethylene high-density (PEHD) is a thermoplastic polymer produced from the monomer ethylene. It is sometimes called "alkathene" or "polythene" when used for HDPE pipes. With a high strength-to-density ratio, ...]
(HDPE) with the added traits of being resistant to concentrated
acid
In computer science, ACID ( atomicity, consistency, isolation, durability) is a set of properties of database transactions intended to guarantee data validity despite errors, power failures, and other mishaps. In the context of databases, a sequ ...
s and
alkali
In chemistry, an alkali (; from ar, القلوي, al-qaly, lit=ashes of the saltwort) is a basic, ionic salt of an alkali metal or an alkaline earth metal. An alkali can also be defined as a base that dissolves in water. A solution of a ...
s, as well as numerous organic solvents. It is highly resistant to corrosive chemicals except
oxidizing acid
An oxidizing acid is a Brønsted acid that is a strong oxidizing agent. Most Brønsted acids can act as oxidizing agents, because the acidic proton can be reduced to hydrogen gas. Some acids contain other structures that act as stronger oxidizing ...
s; has extremely low moisture absorption and a very low
coefficient of friction
Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. There are several types of friction:
*Dry friction is a force that opposes the relative lateral motion of ...
; is self-lubricating (see
boundary lubrication
Lubrication is the process or technique of using a lubricant to reduce friction and wear and tear in a contact between two surfaces. The study of lubrication is a discipline in the field of tribology.
Lubrication mechanisms such as fluid-lubrica ...
); and is highly resistant to
abrasion, in some forms being 15 times more resistant to abrasion than
carbon steel
Carbon steel is a steel with carbon content from about 0.05 up to 2.1 percent by weight. The definition of carbon steel from the American Iron and Steel Institute (AISI) states:
* no minimum content is specified or required for chromium, cobalt ...
. Its coefficient of friction is significantly lower than that of
nylon
Nylon is a generic designation for a family of synthetic polymers composed of polyamides ( repeating units linked by amide links).The polyamides may be aliphatic or semi-aromatic.
Nylon is a silk-like thermoplastic, generally made from petro ...
and
acetal
In organic chemistry, an acetal is a functional group with the connectivity . Here, the R groups can be organic fragments (a carbon atom, with arbitrary other atoms attached to that) or hydrogen, while the R' groups must be organic fragments no ...
and is comparable to that of
polytetrafluoroethylene
Polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer of tetrafluoroethylene that has numerous applications. It is one of the best-known and widely applied PFAS. The commonly known brand name of PTFE-based composition is Teflon by Chemour ...
(PTFE, Teflon), but UHMWPE has better abrasion resistance than PTFE.
Development
Polymerization of UHMWPE was commercialized in the 1950s by
Ruhrchemie AG,
which has changed names over the years. Today UHMWPE powder materials, which may be directly molded into a product's final shape, are produced by,
Ticona
Celanese Corporation, formerly known as Hoechst Celanese, is an American technology and specialty materials company headquartered in Irving, Texas. A Fortune 500 corporation, the company is the world’s leading producer of acetic acid, produc ...
,
Braskem
Braskem is a Brazilian petrochemical company headquartered in São Paulo. The company is the largest petrochemical company in Latin America and has become a major player in the international petrochemical market (8th largest resin producer worldw ...
,
Teijin
is a Japanese chemical industry, chemical, pharmaceutical industry, pharmaceutical and information technology company. Its main fields of operation are high-performance fibers such as aramid, carbon fibers & composites, healthcare, films, resin & ...
(Endumax),
Celanese
Celanese Corporation, formerly known as Hoechst Celanese, is an American technology and specialty materials company headquartered in Irving, Texas. A Fortune 500 corporation, the company is the world’s leading producer of acetic acid, produc ...
, and
Mitsui
is one of the largest '' keiretsu'' in Japan and one of the largest corporate groups in the world.
The major companies of the group include Mitsui & Co. ( general trading company), Sumitomo Mitsui Banking Corporation, Nippon Paper Industri ...
. Processed UHMWPE is available commercially either as fibers or in consolidated form, such as sheets or rods. Because of its resistance to wear and impact, UHMWPE continues to find increasing industrial applications, including the automotive and bottling sectors. Since the 1960s, UHMWPE has also been the material of choice for total joint
arthroplasty
Arthroplasty (literally " e-orming of joint") is an orthopedic surgical procedure where the articular surface of a musculoskeletal joint is replaced, remodeled, or realigned by osteotomy or some other procedure. It is an elective procedure that i ...
in
orthopedic
Orthopedic surgery or orthopedics ( alternatively spelt orthopaedics), is the branch of surgery concerned with conditions involving the musculoskeletal system. Orthopedic surgeons use both surgical and nonsurgical means to treat musculoskeletal ...
and
spine implants.
UHMWPE fibers branded as Dyneema, commercialized in the late 1970s by the Dutch chemical company
DSM
DSM or dsm may refer to:
Science and technology
* Deep space maneuver
* Design structure matrix or dependency structure matrix, a representation of a system or project
* Diagnostic and Statistical Manual of Mental Disorders
** DSM-5, the fifth ed ...
, and Spectra, commercialized by Honeywell (then AlliedSignal) are widely used in ballistic protection, defense applications, and increasingly in medical devices, sailing, hiking equipment, climbing, and many other industries.
Structure and properties
![Polyethylene repeat unit](https://upload.wikimedia.org/wikipedia/commons/4/45/Polyethylene_repeat_unit.svg)
UHMWPE is a type of
polyolefin
A polyolefin is a type of polymer with the general formula (CH2CHR)n where R is an alkyl group. They are usually derived from a small set of simple olefins (alkenes). Dominant in a commercial sense are polyethylene and polypropylene. More speciali ...
. It is made up of extremely long chains of polyethylene, which all align in the same direction. It derives its strength largely from the length of each individual molecule (chain).
Van der Waals forces
In molecular physics, the van der Waals force is a distance-dependent interaction between atoms or molecules. Unlike ionic bond, ionic or covalent bonds, these attractions do not result from a Chemical bond, chemical electronic bond; they are c ...
between the molecules are relatively weak for each atom of overlap between the molecules, but because the molecules are very long, large overlaps can exist, adding up to the ability to carry larger shear forces from molecule to molecule. Each chain is attracted to the others with so many van der Waals forces that the whole of the inter-molecular strength is high. In this way, large
tensile
In physics, tension is described as the pulling force transmitted axially by the means of a string, a rope, chain, or similar object, or by each end of a rod, truss member, or similar three-dimensional object; tension might also be described as t ...
loads are not limited as much by the comparative weakness of each localized van der Waals force.
When formed into fibers, the polymer chains can attain a parallel orientation greater than 95% and a level of
crystallinity
Crystallinity refers to the degree of structural order in a solid. In a crystal, the atoms or molecules are arranged in a regular, periodic manner. The degree of crystallinity has a big influence on hardness, density, Transparency and translucen ...
from 39% to 75%. In contrast,
Kevlar
Kevlar (para-aramid) is a strong, heat-resistant synthetic fiber, related to other aramids such as Nomex and Technora. Developed by Stephanie Kwolek at DuPont in 1965, the high-strength material was first used commercially in the early 1970s a ...
derives its strength from strong bonding between relatively short molecules.
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
The melting point (or, rarely, liquefaction point) of a substance is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depends ...
is around , and, according to DSM, it is not advisable to use UHMWPE fibres at temperatures exceeding for long periods of time. It becomes
brittle
A material is brittle if, when subjected to stress, it fractures with little elastic deformation and without significant plastic deformation. Brittle materials absorb relatively little energy prior to fracture, even those of high strength. Bre ...
at temperatures below .
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
Polar may refer to:
Geography
Polar may refer to:
* Geographical pole, either of two fixed points on the surface of a rotating body or planet, at 90 degrees from the equator, based on the axis around which a body rotates
* Polar climate, the c ...
groups in most polymers easily bond to water. Because olefins have no such groups, UHMWPE does not absorb water readily, nor
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. In a similar manner,
aromatic
In chemistry, aromaticity is a chemical property of cyclic ( ring-shaped), ''typically'' planar (flat) molecular structures with pi bonds in resonance (those containing delocalized electrons) that gives increased stability compared to satur ...
polymers are often susceptible to aromatic solvents due to
aromatic stacking interactions, an effect
aliphatic
In organic chemistry, hydrocarbons ( compounds composed solely of carbon and hydrogen) are divided into two classes: aromatic compounds and aliphatic compounds (; G. ''aleiphar'', fat, oil). Aliphatic compounds can be saturated, like hexane, ...
polymers like UHMWPE are immune to. Since UHMWPE does not contain chemical groups (such as
ester
In chemistry, an ester is a compound derived from an oxoacid (organic or inorganic) in which at least one hydroxyl group () is replaced by an alkoxy group (), as in the substitution reaction of a carboxylic acid and an alcohol. Glycerides ar ...
s,
amide
In organic chemistry, an amide, also known as an organic amide or a carboxamide, is a compound with the general formula , where R, R', and R″ represent organic groups or hydrogen atoms. The amide group is called a peptide bond when it is ...
s or
hydroxyl
In chemistry, a hydroxy or hydroxyl group is a functional group with the chemical formula and composed of one oxygen atom covalently bonded to one hydrogen atom. In organic chemistry, alcohols and carboxylic acids contain one or more hydroxy ...
ic groups) that are susceptible to attack from aggressive agents, it is very resistant to water, moisture, most chemicals, UV radiation, and micro-organisms.
Under tensile load, UHMWPE will deform continually as long as the stress is present—an effect called ''
creep''.
When UHMWPE is
annealed, the material is heated to between 135 °C and 138 °C in an oven or a liquid bath of
silicone oil
A silicone oil is any liquid polymerized siloxane with organic side chains. The most important member is polydimethylsiloxane. These polymers are of commercial interest because of their relatively high thermal stability, lubricating, and Liquid di ...
or
glycerine
Glycerol (), also called glycerine in British English and glycerin in American English, is a simple triol compound. It is a colorless, odorless, viscous liquid that is sweet-tasting and non-toxic. The glycerol backbone is found in lipids known ...
. The material is then cooled down at a rate of 5 °C/h to 65 °C or less. Finally, the material is wrapped in an insulating blanket for 24 hours to bring to room temperature.
Production
''Ultra-high-molecular-weight polyethylene'' (UHMWPE) is
synthesized from its
monomer
In chemistry, a monomer ( ; ''mono-'', "one" + '' -mer'', "part") is a molecule that can react together with other monomer molecules to form a larger polymer chain or three-dimensional network in a process called polymerization.
Classification
Mo ...
ethylene
Ethylene (IUPAC name: ethene) is a hydrocarbon which has the formula or . It is a colourless, flammable gas with a faint "sweet and musky" odour when pure. It is the simplest alkene (a hydrocarbon with carbon-carbon double bonds).
Ethylene i ...
, which is bonded together to form the base polyethylene product. These molecules are several
orders of magnitude
An order of magnitude is an approximation of the logarithm of a value relative to some contextually understood reference value, usually 10, interpreted as the base of the logarithm and the representative of values of magnitude one. Logarithmic dis ...
longer than those of familiar
high-density polyethylene
High-density polyethylene (HDPE) or polyethylene high-density (PEHD) is a thermoplastic polymer produced from the monomer ethylene. It is sometimes called "alkathene" or "polythene" when used for HDPE pipes. With a high strength-to-density ratio, ...
(HDPE) due to a synthesis process based on
metallocene
A metallocene is a compound typically consisting of two cyclopentadienyl anions (, abbreviated Cp) bound to a metallic element, metal center (M) in the oxidation state II, with the resulting general formula Closely related to the metallocenes are ...
catalysts
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 ...
, resulting in UHMWPE molecules typically having 100,000 to 250,000 monomer units per molecule each compared to HDPE's 700 to 1,800 monomers.
UHMWPE is processed variously by
compression moulding
Compression molding is a method of molding in which the molding material, generally preheated, is first placed in an open, heated mold cavity. The mold is closed with a top force or plug member, pressure is applied to force the material int ...
, ram
extrusion
Extrusion is a process used to create objects of a fixed cross-sectional profile by pushing material through a die of the desired cross-section. Its two main advantages over other manufacturing processes are its ability to create very complex c ...
,
gel spinning
A gel is a semi-solid that can have properties ranging from soft and weak to hard and tough. Gels are defined as a substantially dilute cross-linked system, which exhibits no flow when in the steady-state, although the liquid phase may still di ...
, and
sintering
Clinker nodules produced by sintering
Sintering or frittage is the process of compacting and forming a solid mass of material by pressure or heat without melting it to the point of liquefaction.
Sintering happens as part of a manufacturing ...
. Several European companies began compression molding UHMWPE in the early 1960s. Gel-spinning arrived much later and was intended for different applications.
In gel spinning a precisely heated gel of UHMWPE is
extruded
Extrusion is a process used to create objects of a fixed cross-sectional profile by pushing material through a die of the desired cross-section. Its two main advantages over other manufacturing processes are its ability to create very complex c ...
through a
spinneret
A spinneret is a silk-spinning organ of a spider or the larva of an insect. Some adult insects also have spinnerets, such as those borne on the forelegs of Embioptera. Spinnerets are usually on the underside of a spider's opisthosoma, and are ...
. The extrudate is drawn through the air and then cooled in a water bath. The end-result is a fiber with a high degree of molecular orientation, and therefore exceptional
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 ...
. Gel spinning depends on isolating individual chain molecules in the solvent so that intermolecular
entanglements
''Entanglements'' is the third full-length album from indie rock ensemble Parenthetical Girls.
Track listing
#"Four Words" - 3:10
#"Avenue of Trees" - 3:17
#"Unmentionables" - 1:51
#"Gut Symmetries" - 3:58
#"A Song for Ellie Greenwich
Ele ...
are minimal. Entanglements make chain orientation more difficult, and lower the strength of the final product.
Applications
Fiber
![LIROS Dyneema hollow](https://upload.wikimedia.org/wikipedia/commons/a/a4/LIROS_Dyneema_hollow.jpg)
Dyneema and Spectra are
brand
A brand is a name, term, design, symbol or any other feature that distinguishes one seller's good or service from those of other sellers. Brands are used in business, marketing, and advertising for recognition and, importantly, to create an ...
s of lightweight high-strength oriented-strand gels spun through a
spinneret
A spinneret is a silk-spinning organ of a spider or the larva of an insect. Some adult insects also have spinnerets, such as those borne on the forelegs of Embioptera. Spinnerets are usually on the underside of a spider's opisthosoma, and are ...
. They have
yield strength
In materials science and engineering, the yield point is the point on a stress-strain curve that indicates the limit of elastic behavior and the beginning of plastic behavior. Below the yield point, a material will deform elastically and wi ...
s as high as 2.4
GPa
Grading in education is the process of applying standardized measurements for varying levels of achievements in a course. Grades can be assigned as letters (usually A through F), as a range (for example, 1 to 6), as a percentage, or as a numbe ...
(2.4 kN/mm
2 or 350,000
psi
Psi, PSI or Ψ may refer to:
Alphabetic letters
* Psi (Greek) (Ψ, ψ), the 23rd letter of the Greek alphabet
* Psi (Cyrillic) (Ѱ, ѱ), letter of the early Cyrillic alphabet, adopted from Greek
Arts and entertainment
* "Psi" as an abbreviatio ...
) and
density
Density (volumetric mass density or specific mass) is the substance's mass per unit of volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' can also be used. Mathematical ...
as low as 0.97 g/cm
3 (for Dyneema SK75). High-strength steels have comparable yield strengths, and low-carbon steels have yield strengths much lower (around 0.5 GPa). Since steel has a specific gravity of roughly 7.8, these materials have a strength-to-weight ratios eight times that of high-strength steels. Strength-to-weight ratios for UHMWPE are about 40% higher than for
aramid
Aramid fibers, short for aromatic polyamide, are a class of heat-resistant and strong synthetic fibers. They are used in aerospace and military applications, for ballistic-rated body armor fabric and ballistic composites, in marine cordage, ma ...
. The high qualities of UHMWPE filament were discovered by Albert Pennings in 1968 but commercially viable products were made available by DSM in 1990 an
Southern Ropessoon after..
Derivatives of UHMWPE yarn are used in composite plates in
armor
Armour (British English) or armor (American English; see spelling differences) is a covering used to protect an object, individual, or vehicle from physical injury or damage, especially direct contact weapons or projectiles during combat, or fr ...
, in particular,
personal armor
Body armor, also known as body armour, personal armor or armour, or a suit or coat of armor, is protective clothing designed to absorb or deflect physical attacks. Historically used to protect military personnel, today it is also used by variou ...
and on occasion as
vehicle armor
Military vehicles are commonly armoured (or armored; see spelling differences) to withstand the impact of shrapnel, bullets, shells, rockets, and missiles, protecting the personnel inside from enemy fire. Such vehicles include armoured fighting ...
. Civil applications containing UHMWPE fibers are cut-resistant gloves, tear-resistant
hosiery
Hosiery, also referred to as legwear, describes garments worn directly on the feet and legs. The term originated as the collective term for products of which a maker or seller is termed a hosier; and those products are also known generically as h ...
,
bow strings,
climbing equipment
A wide range of equipment is used during rock or any other type of climbing that includes equipment commonly used to protect a climber against the consequences of a fall.
Rope, cord and webbing
Climbing ropes are typically of kernmantle c ...
, automotive
winch
A winch is a mechanical device that is used to pull in (wind up) or let out (wind out) or otherwise adjust the tension of a rope or wire rope (also called "cable" or "wire cable").
In its simplest form, it consists of a spool (or drum) attache ...
ing,
fishing line
A fishing line is a flexible, high-tensile cord used in angling to tether and pull in fish, in conjunction with at least one hook. Fishing lines are usually pulled by and stored in a reel, but can also be retrieved by hand, with a fixed attachm ...
, spear lines for
spearguns, high-performance
sail
A sail is a tensile structure—which is made from fabric or other membrane materials—that uses wind power to propel sailing craft, including sailing ships, sailboats, windsurfers, ice boats, and even sail-powered land vehicles. Sails may ...
s, suspension lines on sport
parachute
A parachute is a device used to slow the motion of an object through an atmosphere by creating drag or, in a ram-air parachute, aerodynamic lift. A major application is to support people, for recreation or as a safety device for aviators, who ...
s and
paraglider
Paragliding is the recreational and competitive adventure sport of flying paragliders: lightweight, free-flying, foot-launched glider aircraft with no rigid primary structure. The pilot sits in a harness or lies supine in a cocoon-like 'po ...
s,
rigging in
yachting
Yachting is the use of recreational boats and ships called ''yachts'' for racing or cruising. Yachts are distinguished from working ships mainly by their leisure purpose. "Yacht" derives from the Dutch word '' jacht'' ("hunt"). With sailboats, t ...
, kites, and kite lines for kites sports.
For personal armor, the fibers are, in general, aligned and bonded into sheets, which are then layered at various angles to give the resulting
composite material
A composite material (also called a composition material or shortened to composite, which is the common name) is a material which is produced from two or more constituent materials. These constituent materials have notably dissimilar chemical or ...
strength in all directions. Recently developed additions to the US Military's
Interceptor body armor
The Interceptor Multi-Threat Body Armor System (IBA) is a bullet-resistant body armor system that was used by the United States Armed Forces during the 2000s, with some limited usage into the mid-2010s. IBA and its design replaced the older stan ...
, designed to offer arm and leg protection, are said to utilize a form of UHMWPE fabric. A multitude of UHMWPE woven fabrics are available in the market and are used as shoe liners,
pantyhose
Pantyhose, called sheer tights, or tights, are close-fitting legwear covering the wearer's body from the waist to the toes. Mostly considered to be a garment for women and girls, pantyhose first appeared on store shelves in 1959 for the advert ...
,
fencing clothing, stab resistant vests and as composite liners for vehicles.
The use of UHMWPE rope for automotive winching offers several advantages over the more common steel wire. The key reason for changing to UHMWPE rope is improved safety. The lower mass of UHMWPE rope, coupled with significantly lower elongation at breaking, carries far less energy than steel or nylon, which leads to almost no
snap-back. UHMWPE rope does not develop kinks that can cause weak spots, and any frayed areas that may develop along the surface of the rope cannot pierce the skin like broken wire strands can. UHMWPE rope is less dense than water, making water recoveries easier as the recovery cable is easier to locate than wire. The bright colours available also aid with visibility should the rope become submerged or dirty. Another advantage in automotive applications is the reduced weight of UHMWPE rope over steel cables. A typical 11 mm UHMWPE rope of 30 metres can weigh around 2 kg, the equivalent steel wire rope would weigh around 13 kg. One notable drawback of UHMWPE rope is its susceptibility to UV damage, so many users will fit winch covers in order to protect the cable when not in use. It is also vulnerable to heat damage from contact with hot components.
Spun UHMWPE fibers excel as fishing line, as they have less stretch, are more
abrasion-resistant, and are thinner than the equivalent
monofilament line
Monofilament fishing line (shortened to just mono) is fishing line made from a single fiber of plastic material, as opposed to multifilament or braided fishing lines constructed from multiple strands of fibers. Most fishing lines are now nylon ...
.
In
climbing
Climbing is the activity of using one's hands, feet, or any other part of the body to ascend a steep topographical object that can range from the world's tallest mountains (e.g. the eight thousanders), to small boulders. Climbing is done fo ...
, cord and
webbing
red, blue and black auto_racing.html"_;"title="nylon_webbing_as_used_in_auto_racing">nylon_webbing_as_used_in_auto_racing_harnesses
Webbing_is_a_strong_nylon_webbing_as_used_in_auto_racing_harnesses">auto_racing.html"_;"title="nylon_webbing_as ...
made of combinations of UHMWPE and nylon
yarn
Yarn is a long continuous length of interlocked fibres, used in sewing, crocheting, knitting, weaving, embroidery, ropemaking, and the production of textiles. Thread is a type of yarn intended for sewing by hand or machine. Modern manufact ...
have gained popularity for their low weight and bulk. They exhibit very low elasticity compared to their nylon counterparts, which translates to low
toughness
In materials science and metallurgy, toughness is the ability of a material to absorb energy and plastically deform without fracturing.[lubricity
Lubricity is the measure of the reduction in friction and/or wear by a lubricant. The study of lubrication and wear mechanisms is called tribology.
Measurement of lubricity
The lubricity of a substance is not a material property, and cannot be me ...]
causes poor knot-holding ability, and it is mostly used in pre-sewn 'slings' (loops of webbing) — relying on knots to join sections of UHMWPE is generally not recommended, and if necessary it is recommended to use the
triple fisherman's knot
The triple fisherman's knot is a bend knot, used to join two ends of rope together. It is an extension of the double fisherman's knot and is recommended for tying slippery, stiff ultra-high-molecular-weight polyethylene (UHMWPE) and aramid core ...
rather than the traditional
double fisherman's knot
The double fisherman's knot or grapevine knot is a bend. This knot and the triple fisherman's knot are the variations used most often in climbing, arboriculture, and search and rescue. The knot is formed by tying a double overhand knot, in its ...
.
Ships'
hawser
Hawser () is a nautical term for a thick cable or rope used in mooring or towing a ship.
A hawser passes through a hawsehole, also known as a cat hole, located on the hawse.The American Heritage Dictionary of the English Language, third edition, ...
s and
cables made from the fiber (0.97 specific gravity) float on sea water. "Spectra wires" as they are called in the towing boat community are commonly used for face wires as a lighter alternative to steel wires.
It is used in skis and snowboards, often in combination with
carbon fiber
Carbon fiber-reinforced polymers (American English), carbon-fibre-reinforced polymers (Commonwealth English), carbon-fiber-reinforced plastics, carbon-fiber reinforced-thermoplastic (CFRP, CRP, CFRTP), also known as carbon fiber, carbon compo ...
, reinforcing the
fiberglass
Fiberglass (American English) or fibreglass (Commonwealth English) is a common type of fiber-reinforced plastic using glass fiber. The fibers may be randomly arranged, flattened into a sheet called a chopped strand mat, or woven into glass cloth ...
composite material, adding stiffness and improving its flex characteristics. The UHMWPE is often used as the base layer, which contacts the snow, and includes abrasives to absorb and retain wax.
It is also used in lifting applications, for manufacturing low weight, and heavy duty lifting slings. Due to its extreme abrasion resistance it is also used as an excellent corner protection for synthetic lifting slings.
High-performance lines (such as
backstay
A backstay is a piece of standing rigging on a sailing vessel that runs from the mast to either its transom or rear quarter, counteracting the forestay and jib. It is an important sail trim control and has a direct effect on the shape of the ma ...
s) for
sailing
Sailing employs the wind—acting on sails, wingsails or kites—to propel a craft on the surface of the ''water'' (sailing ship, sailboat, raft, windsurfer, or kitesurfer), on ''ice'' (iceboat) or on ''land'' (land yacht) over a chosen cour ...
and
parasailing
Parasailing, also known as parascending, paraskiing or parakiting, is a recreational kiting activity where a person is towed behind a vehicle while attached to a specially designed canopy wing that resembles a parachute, known as a parasail ...
are made of UHMWPE, due to their low stretch, high strength, and low weight. Similarly, UHMWPE is often used for winch-launching
gliders from the ground, as, in comparison with steel cable, its superior abrasion resistance results in less wear when running along the ground and into the winch, increasing the time between failures. The lower weight on the mile-long cables used also results in higher winch launches.
UHMWPE was used for the 30-kilometre space tether in the ESA/Russian
Young Engineers' Satellite 2
The Young Engineers' Satellite 2 (YES2) is a 36 kg student-built tether satellite that is part of ESA's Foton-M3 microgravity mission. The launch of the Russian Foton-M3 occurred on September 14, 2007, at 13:00 (CEST) by a Soyuz-U launcher. ...
of September, 2007.
Dyneema Composite Fabric (DCF) is a laminated material consisting of a grid of Dyneema threads sandwiched between two thin transparent polyester membranes. This material is very strong for its weight, and was originally developed for use in racing yacht sails under the name 'Cuben Fiber'. More recently it has found new applications, most notably in the manufacture of lightweight and
ultralight
Ultralight aviation (called microlight aviation in some countries) is the flying of lightweight, 1- or 2-seat fixed-wing aircraft. Some countries differentiate between weight-shift control and conventional three-axis control aircraft with ailer ...
camping and backpacking equipment such as tents and backpacks.
In archery, UHMWPE is widely used as a material for bowstrings because of its low creep and stretch compared to, for example,
Dacron
Polyethylene terephthalate (or poly(ethylene terephthalate), PET, PETE, or the obsolete PETP or PET-P), is the most common thermoplastic polymer resin of the polyester family and is used in fibres for clothing, containers for liquids and foods ...
(PET). Besides pure UHMWPE fibers, most manufacturers use blends to further reduce the creep and stretch of the material. In these blends, the UHMWPE fibers are blended with, for example,
Vectran
Vectran is a manufactured fiber, spun from a liquid-crystal polymer (LCP) created by Celanese Corporation and now manufactured by Kuraray. Chemically it is an aromatic polyester produced by the polycondensation of 4-hydroxybenzoic acid and 6-hyd ...
.
In
skydiving
Parachuting, including also skydiving, is a method of transiting from a high point in the atmosphere to the surface of Earth with the aid of gravity, involving the control of speed during the descent using a parachute or parachutes.
For ...
, UHMWPE is one of the most common materials used for suspension lines, largely supplanting the earlier-used
Dacron
Polyethylene terephthalate (or poly(ethylene terephthalate), PET, PETE, or the obsolete PETP or PET-P), is the most common thermoplastic polymer resin of the polyester family and is used in fibres for clothing, containers for liquids and foods ...
, being lighter and less bulky. UHMWPE has excellent strength and wear-resistance, but is not dimensionally stable (i.e. shrinks) when exposed to heat, which leads to gradual and uneven shrinkage of different lines as they are subject to differing amounts of friction during canopy deployment, necessitating periodic line replacement. It is also almost completely inelastic, which can exacerbate the opening shock. For that reason, Dacron lines continue to be used in student and some tandem systems, where the added bulk is less of a concern than the potential for an injurious opening. In turn, in high performance parachutes used for
swooping, UHMWPE is replaced with Vectran and HMA (high-modulus aramid), which are even thinner and dimensionally stable, but exhibit greater wear and require much more frequent maintenance to prevent catastrophic failure. UHMWPE are also used for reserve parachute closing loops when used with
automatic activation device
In skydiving, an automatic activation device (AAD) is a dead man's switch consisting of an electronic-pyrotechnic or mechanical device that automatically opens the main or reserve parachute container at a preset altitude or after a preset time. ...
s, where their extremely low coefficient of friction is critical for proper operation in the event of cutter activation.
Medical
UHMWPE has a clinical history as a
biomaterial
A biomaterial is a substance that has been engineered to interact with biological systems for a medical purpose, either a therapeutic (treat, augment, repair, or replace a tissue function of the body) or a diagnostic one. As a science, biomateria ...
for use in hip, knee, and (since the 1980s), for spine implants.
An online repository of information and review articles related to medical grade UHMWPE, known as the UHMWPE Lexicon, was started online in 2000.
[UHMWPE Lexicon](_blank)
Uhmwpe.org. Retrieved on 2012-06-30.
Joint replacement components have historically been made from "GUR" resins. These powder materials are produced by Ticona, typically converted into semi-forms by companies such as Quadrant and Orthoplastics,
and then machined into implant components and sterilized by device manufacturers.
UHMWPE was first used clinically in 1962 by Sir
John Charnley
Sir John Charnley, (29 August 1911 – 5 August 1982) was an English orthopaedic surgeon. He pioneered the hip replacement operation, which is now one of the most common operations both in the UK and elsewhere in the world, and created the ...
and emerged as the dominant bearing material for total hip and knee replacements in the 1970s.
Throughout its history, there were unsuccessful attempts to modify UHMWPE to improve its clinical performance until the development of highly
cross-link
In chemistry and biology a cross-link is a bond or a short sequence of bonds that links one polymer chain to another. These links may take the form of covalent bonds or ionic bonds and the polymers can be either synthetic polymers or natural ...
ed UHMWPE in the late 1990s.
One unsuccessful attempt to modify UHMWPE was by blending the powder with carbon fibers. This reinforced UHMWPE was released clinically as "Poly Two" by Zimmer in the 1970s.
The carbon fibers had poor compatibility with the UHMWPE matrix and its clinical performance was inferior to virgin UHMWPE.
A second attempt to modify UHMWPE was by high-pressure recrystallization. This recrystallized UHMWPE was released clinically as "Hylamer" by DePuy in the late 1980s.
When gamma irradiated in air, this material exhibited susceptibility to oxidation, resulting in inferior clinical performance relative to virgin UHMWPE. Today, the poor clinical history of Hylamer is largely attributed to its sterilization method, and there has been a resurgence of interest in studying this material (at least among certain research circles).
Hylamer fell out of favor in the United States in the late 1990s with the development of highly cross-linked UHMWPE materials, however negative clinical reports from Europe about Hylamer continue to surface in the literature.
Highly cross-linked UHMWPE materials were clinically introduced in 1998 and have rapidly become the standard of care for
total hip replacement
Hip replacement is a surgical procedure in which the hip joint is replaced by a prosthetic implant, that is, a hip prosthesis. Hip replacement surgery can be performed as a total replacement or a hemi (half) replacement. Such joint replacement ...
s, at least in the United States.
These new materials are cross-linked with gamma or electron beam radiation (50–105 kGy) and then thermally processed to improve their oxidation resistance.
Five-year clinical data, from several centers, are now available demonstrating their superiority relative to conventional UHMWPE for total hip replacement (see
arthroplasty
Arthroplasty (literally " e-orming of joint") is an orthopedic surgical procedure where the articular surface of a musculoskeletal joint is replaced, remodeled, or realigned by osteotomy or some other procedure. It is an elective procedure that i ...
).
Clinical studies are still underway to investigate the performance of highly cross-linked UHMWPE for knee replacement.
In 2007, manufacturers started incorporating anti-oxidants into UHMWPE for hip and knee arthroplasty bearing surfaces.
Vitamin E
Vitamin E is a group of eight fat soluble compounds that include four tocopherols and four tocotrienols. Vitamin E deficiency, which is rare and usually due to an underlying problem with digesting dietary fat rather than from a diet low in vitami ...
(a-tocopherol) is the most common anti-oxidant used in radiation-cross-linked UHMWPE for medical applications. The anti-oxidant helps quench free radicals that are introduced during the irradiation process, imparting improved oxidation resistance to the UHMWPE without the need for thermal treatment. Several companies have been selling antioxidant-stabilized joint replacement technologies since 2007, using both synthetic vitamin E as well as hindered phenol-based antioxidants.
Another important medical advancement for UHMWPE in the past decade has been the increase in use of fibers for
sutures. Medical-grade fibers for surgical applications are produced by DSM under the "Dyneema Purity" trade name.
Manufacturing
UHMWPE is used in the manufacture of
PVC (vinyl) windows and doors, as it can endure the heat required to soften the PVC-based materials and is used as a form/chamber filler for the various PVC shape profiles in order for those materials to be 'bent' or shaped around a template.
UHMWPE is also used in the manufacture of hydraulic seals and bearings. It is best suited for medium mechanical duties in water, oil hydraulics, pneumatics, and unlubricated applications. It has a good abrasion resistance but is better suited to soft mating surfaces.
Wire/cable
Fluoropolymer / HMWPE insulation cathodic protection cable is typically made with dual insulation. It features a primary layer of a fluoropolymer such as
ECTFE
ECTFE (ethylenechlorotrifluoroethylene) is a copolymer of ethylene and chlorotrifluoroethylene. It is a semi-crystalline fluoropolymer (a partially fluorinated polymer) designed to provide chemical resistance in heavy-duty corrosion application ...
which is chemically resistant to chlorine, sulphuric acid and hydrochloric acid. Following the primary layer is an HMWPE insulation layer, which provides pliable strength and allows considerable abuse during installation. The HMWPE jacketing provides mechanical protection as well.
Marine infrastructure
UHMWPE is used in marine structures for the mooring of ships and floating structures in general. The UHMWPE forms the contact surface between the floating structure and the fixed one. Timber was and is used for this application also. UHMWPE is chosen as facing of fender systems for berthing structures because of the following characteristics:
*Wear resistance: best among plastics, better than steel
*Impact resistance: best among plastics, similar to steel
*Low friction (wet and dry conditions): self-lubricating material
See also
*
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 ...
(LDPE)
*
Medium-density polyethylene
Medium-density polyethylene (MDPE) is a type of polyethylene defined by a density range of 0.926–0.940 g/cm3. It is less dense than HDPE, which is more common.
MDPE can be produced by chromium/silica catalysts, Ziegler-Natta catalysts or met ...
(MDPE)
*
Kevlar
Kevlar (para-aramid) is a strong, heat-resistant synthetic fiber, related to other aramids such as Nomex and Technora. Developed by Stephanie Kwolek at DuPont in 1965, the high-strength material was first used commercially in the early 1970s a ...
*
Twaron
Twaron (a brand name of Teijin Aramid) is a para-aramid. It is a heat-resistant and strong synthetic fibre developed in the early 1970s by the Dutch company Akzo Nobel's division Enka BV, later Akzo Industrial Fibers. The research name of the para ...
*
Dyneema Composite Fabric
Dyneema Composite Fabric (DCF), also known as Cuben Fiber (CTF3), is a high-performance non-woven composite material used in high-strength, low-weight applications. It is constructed from a thin sheet of ultra-high-molecular-weight polyethylene ...
References
Further reading
* Southern et al., The Properties of Polyethylene Crystallized Under the Orientation and Pressure Effects of a Pressure Capillary Viscometer, ''
Journal of Applied Polymer Science'' vol. 14, pp. 2305–2317 (1970).
* Kanamoto, On Ultra-High Tensile by Drawing Single Crystal Mats of High Molecular Weight Polyethylene, ''Polymer Journal'' vol. 15, No. 4, pp. 327–329 (1983).
External links
US Patent 5342567 Process for producing high tenacity and high modulus polyethylene fibers, issued 1994-08-30 Polymer Gel Spinning MachineChristine A. Odero, MIT, 1994
Patent application 20070148452 High strength polyethylene fiber, 2007-06-28Analytical techniques to characterize radiation effects on UHMWPE
Next generation orthopedic implants using UHMWPE
Highly crosslinked VE-UHMWPE for hip and knee replacements
*
ttps://www.southernropes.co.uk/pages/our-hmpe HMPE Fibre – How is it made?
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