Ultra-high-molecular-weight polyethylene (UHMWPE, UHMW) is a subset of the
thermoplastic
A thermoplastic, or thermosoftening 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 as ...
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 bott ...
. Also known as high-modulus polyethylene (HMPE), it has extremely long chains, with a
molecular mass
The molecular mass () is the mass of a given molecule, often expressed in units of daltons (Da). Different molecules of the same compound may have different molecular masses because they contain different isotopes of an element. The derived quan ...
typically between 2 and 6 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 rati ...
(HDPE) with the added traits of being resistant to concentrated
acid
An acid is a molecule or ion capable of either donating a proton (i.e. Hydron, hydrogen cation, H+), known as a Brønsted–Lowry acid–base theory, Brønsted–Lowry acid, or forming a covalent bond with an electron pair, known as a Lewis ...
s and alkalis, as well as numerous organic solvents. It is highly resistant to corrosive chemicals except oxidizing acids; has extremely low moisture absorption and a very low coefficient of friction; is self-lubricating (see boundary lubrication); 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 family of synthetic polymers characterised by amide linkages, typically connecting aliphatic or Polyamide#Classification, semi-aromatic groups.
Nylons are generally brownish in color and can possess a soft texture, with some varieti ...
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 n ...
and is comparable to that of
polytetrafluoroethylene
Polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer of tetrafluoroethylene, and has numerous applications because it is chemically inert. The commonly known brand name of PTFE-based composition is Teflon by Chemours, a corporate spin-of ...
(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 Braskem, Teijin (Endumax), Celanese, and Mitsui. 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 in
orthopedic
Orthopedic surgery or orthopedics ( alternative spelling 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, and as Spectra, commercialized by Honeywell (then AlliedSignal), are widely used in ballistic protection, defense applications, and increasingly in medical devices, protective motorcycling gear, sailing, hiking equipment, climbing, and many other industries.
Structure and properties
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 and chemistry, the van der Waals force (sometimes van der Waals' force) is a distance-dependent interaction between atoms or molecules. Unlike ionic or covalent bonds, these attractions do not result from a chemical ele ...
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 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 from 39% to 75%. In contrast, Kevlar 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 of matter, state from solid to liquid. At the melting point the solid and liquid phase (matter), phase exist in Thermodynamic equilib ...
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. ...
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 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 organic chemistry, aromaticity is a chemical property describing the way in which a conjugated system, conjugated ring of unsaturated bonds, lone pairs, or empty orbitals exhibits a stabilization stronger than would be expected from conjugati ...
polymers are often susceptible to aromatic solvents due to aromatic stacking interactions, an effect aliphatic 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 acid (either organic or inorganic) in which the hydrogen atom (H) of at least one acidic hydroxyl group () of that acid is replaced by an organyl group (R). These compounds contain a distin ...
s,
amide
In organic chemistry, an amide, also known as an organic amide or a carboxamide, is a chemical compound, compound with the general formula , where R, R', and R″ represent any group, typically organyl functional group, groups or hydrogen at ...
s, 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.
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 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 and their lubricating prop ...
or glycerine. The material is then cooled down to at a rate of 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
A monomer ( ; ''mono-'', "one" + '' -mer'', "part") is a molecule that can react together with other monomer molecules to form a larger polymer chain or two- or three-dimensional network in a process called polymerization.
Classification
Chemis ...
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 bond, carbon–carbon doub ...
, which is bonded together to form the base polyethylene product. These molecules are several
orders of magnitude
In a ratio scale based on powers of ten, the order of magnitude is a measure of the nearness of two figures. Two numbers are "within an order of magnitude" of each other if their ratio is between 1/10 and 10. In other words, the two numbers are wi ...
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 rati ...
(HDPE) due to a synthesis process based on metallocene
catalysts
Catalysis () is the increase in reaction rate, rate of a chemical reaction due to an added substance known as a catalyst (). Catalysts are not consumed by the reaction and remain unchanged after it. If the reaction is rapid and the catalyst ...
, 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, ram
extrusion
Extrusion is a process used to create objects of a fixed cross section (geometry), cross-sectional profile by pushing material through a Die (manufacturing), die of the desired cross-section. Its two main advantages over other manufacturing pro ...
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 process used with metals, ceramics, plas ...
. Several European companies began compression molding UHMWPE in the early 1960s. Gel-spinning arrived much later and was intended for different applications. The two major producers of UHMWPE yarns via gel spinning are Honeywell and DSM.
In gel spinning a precisely heated gel (of a low concentration of UHMWPE in an oil) is extruded through a spinneret. The extrudate is drawn through the air, the oil extracted with a solvent which does not affect the UHMWPE, and then dried removing the solvent. The end-result is a fiber with a high degree of molecular orientation, and therefore exceptional
tensile strength
Ultimate tensile strength (also called UTS, tensile strength, TS, ultimate strength or F_\text in notation) is the maximum stress that a material can withstand while being stretched or pulled before breaking. In brittle materials, the ultimate ...
. Gel spinning depends on isolating individual chain molecules in the solvent so that intermolecular entanglements are minimal. Entanglements make chain orientation more difficult, and lower the strength of the final product.
Applications
Fiber
Dyneema and Spectra are
brand
A brand is a name, term, design, symbol or any other feature that distinguishes one seller's goods or service from those of other sellers. Brands are used in business, marketing, and advertising for recognition and, importantly, to create and ...
s of lightweight high-strength oriented-strand gels spun through a spinneret. 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 w ...
s as high as and
density
Density (volumetric mass density or specific mass) is the ratio of a substance's mass to its volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' (or ''d'') can also be u ...
as low as (for Dyneema SK75). High-strength steels have comparable yield strengths, and low-carbon steels have yield strengths much lower (around ). 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. The high qualities of UHMWPE filament were discovered by Albert Pennings in 1968, but commercially viable products were made available by DSM in 1990 and Southern Ropes soon after.
Derivatives of UHMWPE yarn are used in composite plates in
armor
Armour (Commonwealth English) or armor (American English; see American and British English spelling differences#-our, -or, spelling differences) is a covering used to protect an object, individual, or vehicle from physical injury or damage, e ...
, in particular, personal armor and on occasion as vehicle armor. Civil applications containing UHMWPE fibers are cut-resistant gloves, tear-resistant
hosiery
Hosiery, (, ) also referred to as legwear, describes garments worn directly on the foot, feet and human leg, 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 ...
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 (physics), tension of a rope or wire rope (also called "cable" or "wire cable").
In its simplest form, it consists of a Bobb ...
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 b ...
s, suspension lines on sport
parachute
A parachute is a device designed to slow an object's descent through an atmosphere by creating Drag (physics), drag or aerodynamic Lift (force), lift. It is primarily used to safely support people exiting aircraft at height, but also serves va ...
s and
paraglider
Paragliding is the recreational and competitive adventure sport of flying paragliders: lightweight, free-flying, foot-launched Glider (aircraft), glider aircraft with no rigid primary structure. The pilot sits in a :wikt:harness, harness or in ...
s,
rigging
Rigging comprises the system of ropes, cables and chains, which support and control a sailing ship or sail boat's masts and sails. ''Standing rigging'' is the fixed rigging that supports masts including shrouds and stays. ''Running rigg ...
in yachting, 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 or composite material (also composition material) is a material which is produced from two or more constituent materials. These constituent materials have notably dissimilar chemical or physical properties and are merged to create a ...
strength in all directions. Recently developed additions to the US Military's Interceptor body armor, 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, fencing clothing, stab-resistant vests, and composite liners for vehicles.
The use of UHMWPE rope for automotive winching offers several advantages over the more common steel
wire rope
Steel wire rope (right hand lang lay)
Wire rope is composed of as few as two solid, metal wires twisted into a helix that forms a composite ''rope'', in a pattern known as ''laid rope''. Larger diameter wire rope consists of multiple strands of ...
. 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 steel wire strands can. UHMWPE rope is less dense than water, making water recoveries easier as the recovery cable is easier to locate than wire rope. 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 UHMWPE rope of can weigh around , the equivalent steel wire rope would weigh around . 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.
In climbing, cord and webbing 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 ...
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 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 rather than the traditional double fisherman's knot.
Ships' hawsers 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 comp ...
, reinforcing the
fiberglass
Fiberglass (American English) or fibreglass (English in the Commonwealth of Nations, Commonwealth English) is a common type of fibre-reinforced plastic, fiber-reinforced plastic using glass fiber. The fibers may be randomly arranged, flattened i ...
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 backstays) 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, Windsurfing, windsurfer, or Kitesurfing, kitesurfer), on ''ice'' (iceboat) or on ''land'' (Land sa ...
and parasailing 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 long, thick space tether in the ESA/Russian Young Engineers' Satellite 2 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 aile ...
camping and backpacking equipment such as tents, backpacks, and bear-proof food bags.
In archery, UHMWPE is widely used as a material for bowstrings because of its low creep and stretch compared to, for example, Dacron (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.
In
skydiving
Parachuting and skydiving are methods of descending from a high point in an atmosphere to the ground or ocean surface with the aid of gravity, involving the control of speed during the descent using a parachute or multiple parachutes.
For hu ...
, UHMWPE is one of the most common materials used for suspension lines, largely supplanting the earlier-used Dacron, 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 devices, 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 Biological engineering, 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 Medical diag ...
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.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 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 replacements, 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). 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 compounds related in molecular structure that includes four tocopherols and four tocotrienols. The tocopherols function as fat-soluble antioxidants which may help protect cell membranes from reactive oxygen speci ...
(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 and cable
Fluoropolymer / HMWPE insulation cathodic protection cable is typically made with dual insulation. It features a primary layer of a fluoropolymer such as ethylene-chlorotrifluoroethylene (ECTFE) which is chemically resistant to chlorine, sulfuric acid, and
hydrochloric acid
Hydrochloric acid, also known as muriatic acid or spirits of salt, is an aqueous solution of hydrogen chloride (HCl). It is a colorless solution with a distinctive pungency, pungent smell. It is classified as a acid strength, strong acid. It is ...
. 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
* 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).