Ethylene-vinyl acetate (EVA), also known as poly(ethylene-vinyl acetate) (PEVA), is a

copolymer In polymer chemistry, a copolymer is a polymer derived from more than one species of monomer. The polymerization of monomers into copolymers is called copolymerization. Copolymers obtained from the copolymerization of two monomer species are som ...

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 ...

and

vinyl acetate Vinyl acetate is an organic compound with the Chemical formula, formula CH3CO2CH=CH2. This colorless liquid is the precursor to polyvinyl acetate, ethylene-vinyl acetate copolymers, polyvinyl alcohol, and other important industrial polymers. Prod ...

. The weight percent of vinyl acetate usually varies from 10 to 50%, with the remainder being ethylene. There are three different types of EVA copolymer, which differ in the

(VA) content and the way the materials are used. The EVA copolymer which is based on a low proportion of VA (approximately up to 4%) may be referred to as vinyl acetate modified polyethylene. It is a copolymer and is processed as a

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 ...

material – just like

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 John C. Swallow and M.W Perrin who were working for Imperial Chemical Industries (ICI) using a high pr ...

. It has some of the properties of a low-density polyethylene but increased gloss (useful for film), softness and flexibility. The material is generally considered non-toxic. The EVA copolymer which is based on a medium proportion of VA (approximately 4 to 30%) is referred to as thermoplastic ethylene-vinyl acetate copolymer and is a thermoplastic elastomer material. It is not

vulcanized Vulcanization (British English: vulcanisation) is a range of processes for hardening rubbers. The term originally referred exclusively to the treatment of natural rubber with sulfur, which remains the most common practice. It has also grown to ...

but has some of the properties of a rubber or of plasticized

polyvinyl chloride Polyvinyl chloride (alternatively: poly(vinyl chloride), colloquial: vinyl or polyvinyl; abbreviated: PVC) is the world's third-most widely produced synthetic polymer of plastic (after polyethylene and polypropylene). About 40 million tons of ...

particularly at the higher end of the range. Both filled and unfilled EVA materials have good low temperature properties and are tough. The materials with approximately 11% VA are used as hot-melt adhesives. The EVA copolymer which is based on a high proportion of VA (greater than 60%) is referred to as ethylene-vinyl acetate rubber. EVA is an

elastomer An elastomer is a polymer with viscoelasticity (i.e. both viscosity and elasticity) and with weak intermolecular forces, generally low Young's modulus (E) and high failure strain compared with other materials. The term, a portmanteau of ''ela ...

polymer A polymer () is a chemical substance, substance or material that consists of very large molecules, or macromolecules, that are constituted by many repeat unit, repeating subunits derived from one or more species of monomers. Due to their br ...

that produces materials which are "rubber-like" in softness and flexibility. The material has good clarity and gloss, low-temperature

toughness In materials science and metallurgy, toughness is the ability of a material to absorb energy and plastically deform without fracturing.adhesive Adhesive, also known as glue, cement, mucilage, or paste, is any non-metallic substance applied to one or both surfaces of two separate items that binds them together and resists their separation. The use of adhesives offers certain advantage ...

waterproof properties, and resistance to

UV radiation Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of t ...

. EVA has a distinctive vinegar-like odor and is competitive with

rubber Rubber, also called India rubber, latex, Amazonian rubber, ''caucho'', or ''caoutchouc'', as initially produced, consists of polymers of the organic compound isoprene, with minor impurities of other organic compounds. Types of polyisoprene ...

and

vinyl polymer In polymer chemistry, vinyl polymers are a group of polymers derived from substituted vinyl () monomers. Their backbone is an extended alkane chain . In popular usage, "vinyl" refers only to polyvinyl chloride (PVC). Examples Vinyl polymers are ...

products in many electrical applications.

Production

EVA is obtained via

chain-growth polymerization Chain-growth polymerization (American English, AE) or chain-growth polymerisation (British English, BE) is a polymerization technique where monomer molecules add onto the active site on a growing polymer chain one at a time. There are a limited n ...

of ethylene and vinyl acetate. There are several techniques of polymerization that can be applied to this polymer, such as solution, suspension, bulk, and emulsion polymerization. A widely used technique consist in high-pressure bulk polymerization process, either in tubolar reactors or autoclave reactors. Although less popular, others processes have been investigated, in particular, one study investigated the feasibility of a continuous emulsion reaction. Typically, this reaction takes place with a

solvent A solvent (from the Latin language, Latin ''wikt:solvo#Latin, solvō'', "loosen, untie, solve") is a substance that dissolves a solute, resulting in a Solution (chemistry), solution. A solvent is usually a liquid but can also be a solid, a gas ...

(when the polymerization process isn't carried in emulsion phase), like a low molecular weight

alcohol Alcohol may refer to: Common uses * Alcohol (chemistry), a class of compounds * Ethanol, one of several alcohols, commonly known as alcohol in everyday life ** Alcohol (drug), intoxicant found in alcoholic beverages ** Alcoholic beverage, an alco ...

, such as

methanol Methanol (also called methyl alcohol and wood spirit, amongst other names) is an organic chemical compound and the simplest aliphatic Alcohol (chemistry), alcohol, with the chemical formula (a methyl group linked to a hydroxyl group, often ab ...

. Usually, the reaction is initiated with a

azo compound Azo compounds are organic compounds bearing the functional group diazenyl (, in which R and R′ can be either aryl or alkyl groups). IUPAC defines azo compounds as: "Derivatives of diazene (diimide), , wherein both hydrogens are substituted ...

or a

peroxide In chemistry, peroxides are a group of Chemical compound, compounds with the structure , where the R's represent a radical (a portion of a complete molecule; not necessarily a free radical) and O's are single oxygen atoms. Oxygen atoms are joined ...

(used between 0.002% and 0.1% w/w). The temperature of reaction is preferably kept between 40°C and 80°C. Conversion rates should not exceed 60%: from a thermodynamic point of view, this is an

exothermic reaction In thermochemistry, an exothermic reaction is a "reaction for which the overall standard enthalpy change Δ''H''⚬ is negative." Exothermic reactions usually release heat. The term is often confused with exergonic reaction, which IUPAC define ...

, and controlling the temperature could be much more difficult if the

viscosity Viscosity is a measure of a fluid's rate-dependent drag (physics), resistance to a change in shape or to movement of its neighboring portions relative to one another. For liquids, it corresponds to the informal concept of ''thickness''; for e ...

is too high. Researchers demonstrated that although EVA is a widely used polymer, the kinetics parameters of the polymerization are incredibly complex. Using computational tools, it was found out that EVA polymerization process mainly consist in four reactions: chain initiation, chain growth, chain transfer, and chain termination. Specifically the chain growth is responsible for the

degree of polymerization The degree of polymerization, or DP, is the number of structural unit, monomeric units in a macromolecule or polymer or oligomer molecule. For a homopolymer, there is only one type of monomeric unit and the ''number-average'' degree of polymeriza ...

and the average molecular weight, the

chain transfer In polymer chemistry, chain transfer is a polymerization reaction by which the activity of a growing polymer chain is transferred to another molecule: \ce^\bullet + \ce^\bullet where • is the active center, P is the initial polymer chain, X i ...

is responsible for the

dispersity In chemistry, the dispersity is a measure of the heterogeneity of sizes of molecules or particles in a mixture. A collection of objects is called uniform if the objects have the same size, shape, or mass. A sample of objects that have an inconsi ...

Chemistry

Hydrolysis of EVA gives

ethylene vinyl alcohol Ethylene vinyl alcohol (EVOH) is a formal copolymer of ethylene and vinyl alcohol. Because the latter monomer mainly exists as its tautomer acetaldehyde, the copolymer is prepared by polymerization of ethylene and vinyl acetate to give the ethy ...

(EVOH) copolymer (and acetic acid).

Applications

File:Worn foam kickboard.jpg, Foam

flutterboard A swimming float, commonly known as pool float or floaty, is a device used for toddlers or other very young children who are beginning to learn how to swim, or during exercise for therapeutic or training purposes. These devices, which come in man ...

File:Material-vylen-crosslinked-pe-eva.jpg, EVA foam sheets File:Kneeling pad 01.JPG, Garden

kneeler A kneeler is a cushion (also called a tuffet, hassock, genuflexorium, or genuflectorium) or a piece of furniture used for resting in a kneeling position during Christian prayer. In many churches, pews are equipped with kneelers in front ...

File:Green flip flops on red background.jpg, Flip-flop sole File:HK Fashion Plastic Clogs n Shoes n Colourful Crocs Footwear.JPG, Foam

Crocs Crocs, Inc. is an American footwear company based in Broomfield, Colorado. It manufactures and markets the Crocs brand of foam footwear. Crocs, Inc. terms these "clogs," but they do not contain wood like traditional clogs. History 2002–20 ...

File:Green yoga block.jpg,

Yoga block Yoga (UK: , US: ; 'yoga' ; ) is a group of Asana, physical, mental, and Spirituality#Asian traditions, spiritual practices or disciplines that originated with Yoga (philosophy), its own philosophy in History of India, ancient India, aime ...

s are commonly made of EVA, as are some mats File:Hopscotch on foam board.jpg, Interlocking floor tiles are often made from EVA foam Hot-melt adhesives (such as hot glue sticks) and top-of-the-line

football boots Football boots, also referred to as cleats or soccer shoes in North America, are specialized footwear designed for use in association football. Those designed for grass pitches have studs on the outsole to aid grip. Modern football boots are ...

(cleats) are usually made from EVA, generally with additives like

wax Waxes are a diverse class of organic compounds that are lipophilic, malleable solids near ambient temperatures. They include higher alkanes and lipids, typically with melting points above about 40 °C (104 °F), melting to give lo ...

and

resin A resin is a solid or highly viscous liquid that can be converted into a polymer. Resins may be biological or synthetic in origin, but are typically harvested from plants. Resins are mixtures of organic compounds, predominantly terpenes. Commo ...

. EVA is also used as a clinginess-enhancing additive in plastic wraps. Craft-foam sheets are made of EVA and are popularly used for children's foam stickers. EVA is also used in

biomedical engineering Biomedical engineering (BME) or medical engineering is the application of engineering principles and design concepts to medicine and biology for healthcare applications (e.g., diagnostic or therapeutic purposes). BME also integrates the logica ...

applications as a drug-delivery device. The polymer is dissolved in an organic solvent (such as

dichloromethane Dichloromethane (DCM, methylene chloride, or methylene bichloride) is an organochlorine compound with the formula . This colorless, volatile liquid with a chloroform-like, sweet odor is widely used as a solvent. Although it is not miscible with ...

). Powdered drug and filler (typically an inert sugar) are added to the liquid solution and rapidly mixed to obtain a homogeneous mixture. The drug-filler-polymer mixture is then cast into a mold at −80 °C and freeze-dried until solid. These devices are used in drug delivery research to slowly release a compound. The polymer does not biodegrade within the body, but is quite inert and causes little or no reaction following implantation. EVA is one of the materials popularly known as ''expanded rubber'' or ''foam rubber''. EVA

foam Foams are two-phase materials science, material systems where a gas is dispersed in a second, non-gaseous material, specifically, in which gas cells are enclosed by a distinct liquid or solid material. Note, this source focuses only on liquid ...

is used as padding in equipment for various sports such as

ski boots Ski boots are footwear used in skiing to provide a way to attach the skier to skis using ski bindings. The ski/boot/binding combination is used to effectively transmit control inputs from the skier's legs to the snow. History Ski boots were leat ...

bicycle A bicycle, also called a pedal cycle, bike, push-bike or cycle, is a human-powered transport, human-powered or motorized bicycle, motor-assisted, bicycle pedal, pedal-driven, single-track vehicle, with two bicycle wheel, wheels attached to a ...

saddles,

hockey ''Hockey'' is a family of List of stick sports, stick sports where two opposing teams use hockey sticks to propel a ball or disk into a goal. There are many types of hockey, and the individual sports vary in rules, numbers of players, apparel, ...

pads,

boxing Boxing is a combat sport and martial art. Taking place in a boxing ring, it involves two people – usually wearing protective equipment, such as boxing glove, protective gloves, hand wraps, and mouthguards – throwing Punch (combat), punch ...

and mixed-martial-arts gloves and helmets,

wakeboard Wakeboarding is a water sport in which the rider, standing on a wakeboard (a board with foot bindings), is towed behind a motorboat across its wake and especially up off the crest in order to perform aerial maneuvers. A hallmark of wakeboarding ...

boots,

waterski Water skiing (also waterskiing or water-skiing) is a Surface water sports, surface water sport in which an individual is pulled behind a boat or a Cable skiing, cable ski installation over a body of water, skimming the surface on one or two s ...

boots,

fishing rod A fishing rod or fishing pole is a long, thin rod used by angling, anglers to fishing, catch fish by manipulating a fishing line, line ending in a fish hook, hook (formerly known as an ''angle'', hence the term "angling"). At its most basic ...

s, and fishing-reel handles. It is typically used as a

shock absorber A shock absorber or damper is a mechanical or hydraulics, hydraulic device designed to absorb and Damping ratio, damp shock (mechanics), shock impulses. It does this by converting the kinetic energy of the shock into another form of energy (typic ...

in sports shoes, for example. (Some manufacturers of running shoes, such as

Nike Nike often refers to: * Nike, Inc., a major American producer of athletic shoes, apparel, and sports equipment * Nike (mythology), a Greek goddess who personifies victory Nike may also refer to: People * Nike (name), a surname and feminine giv ...

, market EVA-based compression-moulded foam used in the manufacture of running shoes as "Phylon".) It is used for the manufacture of floats for commercial fishing gear such as purse seine (

seine fishing Seine fishing (or seine-haul fishing; ) is a method of fishing that employs a surrounding net, called a seine, that hangs vertically in the water with its bottom edge held down by weights and its top edge buoyed by floats. Seine nets can be dep ...

) and

gillnets Gillnetting is a fishing method that uses gillnets: vertical panels of netting that hang from a line with regularly spaced floaters that hold the line on the surface of the water. The floats are sometimes called "corks" and the line with corks is ...

. In addition, because of its buoyancy, EVA has made its way into non-traditional products such as floating eyewear. It is also used in the

photovoltaic Photovoltaics (PV) is the conversion of light into electricity using semiconducting materials that exhibit the photovoltaic effect, a phenomenon studied in physics, photochemistry, and electrochemistry. The photovoltaic effect is commercially ...

s industry as an encapsulation material for

crystalline silicon Crystalline silicon or (c-Si) is the crystalline forms of silicon, either polycrystalline silicon (poly-Si, consisting of small crystals), or monocrystalline silicon (mono-Si, a continuous crystal). Crystalline silicon is the dominant semicon ...

solar cells A solar cell, also known as a photovoltaic cell (PV cell), is an electronic device that converts the energy of light directly into electricity by means of the photovoltaic effect.

in the manufacture of

photovoltaic module Photovoltaics (PV) is the conversion of light into electricity using semiconducting materials that exhibit the photovoltaic effect, a phenomenon studied in physics, photochemistry, and electrochemistry. The photovoltaic effect is commerciall ...

s. EVA slippers and sandals are popular, being lightweight, easy to form, odourless, glossy, and cheaper than natural rubber. In fishing rods, EVA is used to construct handles on the rod-butt end. EVA can be used as a substitute for

cork "Cork" or "CORK" may refer to: Materials * Cork (material), an impermeable buoyant plant product ** Stopper (plug), or "cork", a cylindrical or conical object used to seal a container *** Wine cork an item to seal or reseal wine Places Ireland * ...

in many applications. EVA copolymers are adhesives used in packaging, textile, bookbinding for bonding plastic films, metal surfaces,

coated paper Coated paper (also known as enamel paper, gloss paper, and thin paper) is paper that has been coated with a mixture of materials or a polymer to impart certain qualities to the paper, including weight, surface gloss, smoothness, or reduced ink ab ...

, and as redispersible powders in

plaster Plaster is a building material used for the protective or decorative coating of walls and ceilings and for moulding and casting decorative elements. In English, "plaster" usually means a material used for the interiors of buildings, while "re ...

s and

cement render Cement render or cement plaster is the application of a mortar mix of sand and cement, (optionally lime) and water to brick, concrete, stone, or mud brick. It is often textured, colored, or painted after application. It is generally used on ...

s. In recent years, EVA foam has seen popular use in

cosplay Cosplay, a blend word of "costume play", is an activity and performance art in which participants called cosplayers wear costumes and Fashion accessory, fashion accessories to represent a specific Character (arts), character. Cosplayers often i ...

communities, largely in part due to its ease to work with, durability, and comfort in comparison to traditional plastic-based costumes. Flower-making foam is a thin sheet made of EVA, which is flexible, and is used by artists and craft makers to make artificial flowers. These foams are presented as raw sheets and they can be cut into the desired petal shape and then can be formed by ironing to assemble artificial flowers by putting these petals together. EVA is also used in coatings formulation of good-quality interior water-borne

paint Paint is a material or mixture that, when applied to a solid material and allowed to dry, adds a film-like layer. As art, this is used to create an image or images known as a painting. Paint can be made in many colors and types. Most paints are ...

s at 53% primary dispersant.

Other uses

EVA is used in orthotics, surfboard and skimboard traction pads, car mats, and for the manufacturing of some artificial flowers. EVA is used as a cold flow improver for diesel fuel. They are added at the 50-250 ppm level to diesel fuels to inhibit crystallization of waxes which could block fuel filters. EVA is a separator in

HEPA filter HEPA (, high efficiency particulate air) filter, also known as a high efficiency particulate arresting filter, is an efficiency standard of air filters. Filters meeting the HEPA standard must satisfy certain levels of efficiency. Common standa ...

s. EVA can easily be cut from sheets and molded to shape. It is also used to make thermoplastic

mouthguards A mouthguard is a protective device for the Human mouth, mouth that covers the teeth and gums to prevent and reduce injury to the Human teeth, teeth, arches, lips and Gingiva, gums. An effective mouthguard is like a crash helmet for teeth and j ...

that soften in boiling water for a user-specific fit. It is also used for conditioning and waterproofing fabrics and leather. EVA finds application in the making of nicotine

transdermal patches A transdermal patch is a medicated adhesive patch that is placed on the skin to deliver a specific dose of medication through the skin and into the bloodstream. An advantage of a transdermal drug delivery route over other types of medic ...

, since the copolymer binds well with other agents to form gel-like substances. EVA is also sometimes used as a material for some plastic model kit parts. One common use of EVA foam rubber is in low frequency (woofer) speaker cone membrane support rings (replacing rubber) because of its good mechanical and acoustic properties. Open cell EVA foam is used to damp high frequency acoustical diffraction from tweeter speakers and is often put in the area around the high frequency speaker driver to give better directivity and sonic imaging. EVA may be used in custom-made dental devices with a proper approach to hygiene.

Safety and environmental considerations

Polyethylene vinyl acetate has recently become a popular alternative to

because it does not contain

chlorine Chlorine is a chemical element; it has Symbol (chemistry), symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between ...

. As of 2014, EVA has not been found to be carcinogenic by the NTP,

ACGIH The American Conference of Governmental Industrial Hygienists (ACGIH) is a professional association of industrial hygienists and practitioners of related professions, with headquarters in Cincinnati, Ohio. One of its goals is to advance worker pr ...

IARC IARC may refer to: * International Aerial Robotics Competition * International Age Rating Coalition * International Agency for Research on Cancer * International Arctic Research Center * Israel Association of Radio Communication * iArc, South Ko ...

, or

OSHA The Occupational Safety and Health Administration (OSHA; ) is a regulatory agency of the United States Department of Labor that originally had federal visitorial powers to inspect and examine workplaces. The United States Congress established ...

, and has no known adverse effect on human health. Like many plastics, it is difficult to biodegrade. One study suggested it may have adverse effects on certain organisms, but its actual effect on humans has not been determined.

References

External links

List of EVA tradenames
(2007; last update 2008; last archived 2022) {{Plastics Acetate esters Commodity chemicals Copolymers Elastomers Plastics Thermoplastics Vinyl polymers