Ethylene-vinyl acetate (EVA), also known as poly (ethylene-vinyl acetate) (PEVA), is the
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 some ...
vinyl acetate
Vinyl acetate is an organic compound with the formula CH3CO2CH=CH2. This colorless liquid is the precursor to polyvinyl acetate and ethene-vinyl acetate copolymers, important industrial polymers.
Production
The worldwide production capacity of v ...
. The weight percent of vinyl acetate usually varies from 10 to 40%, with the remainder being ethylene. There are three different types of EVA copolymer, which differ in the vinyl acetate (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 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 ...
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 Imperial Chemical Industries (ICI) using a high pressure process via free radical polymerization. Its ...
. 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: 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 inclu ...
but has some of the properties of a rubber or of plasticized polyvinyl chloride 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 elastomeric
polymer
A polymer (; Greek '' poly-'', "many" + ''-mer'', "part")
is a substance or material consisting of very large molecules called macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic a ...
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 waterproof properties, and resistance to
UV radiation
Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30 PHz) to 400 nm (750 THz), shorter than that of visible light, but longer than X-rays. UV radiation i ...
. 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. Thailand, Malaysia, an ...
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 ...
products in many electrical applications.
Production
Applications
File:Worn foam kickboard.jpg, Foam flutterboard
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 or hassock) 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 of the seating bench so members of ...
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. (stylized in all lowercase) is an American footwear company based in Broomfield, Colorado, that manufactures and markets the Crocs brand of foam clogs.
History
Crocs was founded by Lyndon "Duke" Hanson, and George Boedecker Jr. to ...
File:Armor made from EVA foam.jpg, Cosplay "armour"
File:Green yoga block.jpg,
Yoga block
A yoga brick or yoga block is a smooth block of wood or of firm but comfortable material, such as hard foam rubber or cork, used as a prop in yoga as exercise.
The use of wooden bricks to assist in alignment was introduced by B. K. S. Iyengar, ...
s are commonly made of EVA, as are some mats
Hot melt adhesive
Hot-melt adhesive (HMA), also known as hot glue, is a form of thermoplastic adhesive that is commonly sold as solid cylindrical sticks of various diameters designed to be applied using a hot glue gun. The gun uses a continuous-duty heating elem ...
s (such as hot glue sticks) and top-of-the-line soccer 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 giv ...
and
resin
In polymer chemistry and materials science, resin is a solid or highly viscous substance of plant or synthetic origin that is typically convertible into polymers. Resins are usually mixtures of organic compounds. This article focuses on n ...
. EVA is also used as a clinginess-enhancing additive in
plastic wrap
Plastic wrap, cling film, Saran wrap, cling wrap, Glad wrap or food wrap is a thin plastic film typically used for sealing food items in containers to keep them fresh over a longer period of time. Plastic wrap, typically sold on rolls in boxe ...
s. 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 purposes (e.g., diagnostic or therapeutic). BME is also traditionally logical sciences ...
applications as a drug-delivery device. The polymer is dissolved in an organic solvent (such as dichloromethane). 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
Biodegradation is the breakdown of organic matter by microorganisms, such as bacteria and fungi. It is generally assumed to be a natural process, which differentiates it from composting. Composting is a human-driven process in which biodegradati ...
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 materials formed by trapping pockets of gas in a liquid or solid.
A bath sponge and the head on a glass of beer are examples of foams. In most foams, the volume of gas is large, with thin films of liquid or solid separating the ...
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 ...
hockey
Hockey is a term used to denote a family of various types of both summer and winter team sports which originated on either an outdoor field, sheet of ice, or dry floor such as in a gymnasium. While these sports vary in specific rules, numbers o ...
pads,
boxing
Boxing (also known as "Western boxing" or "pugilism") is a combat sport in which two people, usually wearing protective gloves and other protective equipment such as hand wraps and mouthguards, throw punches at each other for a predetermine ...
waterski
Water skiing (also waterskiing or water-skiing) is a surface water sport in which an individual is pulled behind a boat or a cable ski installation over a body of water, skimming the surface on two skis or one ski. The sport requires suffic ...
Nike
Nike often refers to:
* Nike (mythology), a Greek goddess who personifies victory
* Nike, Inc., a major American producer of athletic shoes, apparel, and sports equipment
Nike may also refer to:
People
* Nike (name), a surname and feminine give ...
, 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 de ...
) 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 photovoltaics 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 semiconduc ...
solar cells
A solar cell, or photovoltaic cell, is an electronic device that converts the energy of light directly into electricity by the photovoltaic effect, which is a physical and chemical phenomenon.
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 commercially us ...
s. EVA slippers and sandals are popular, being lightweight, easy to form, odourless, glossy, and cheaper compared to 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
** Cork (plug), a cylindrical or conical object used to seal a container
***Wine cork
Places Ireland
* Cork (city)
** Metropolitan Cork, also known as G ...
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 by a mixture of materials or a polymer to impart certain qualities to the paper, including weight, surface gloss, smoothness, or reduced ink absor ...
and as redispersible powders in
plaster
Plaster is a building material used for the protective or decorative coating of walls and ceilings and for Molding (decorative), moulding and casting decorative elements. In English, "plaster" usually means a material used for the interiors of ...
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 portmanteau of "costume play", is an activity and performance art in which participants called cosplayers wear costumes and fashion accessories to represent a specific character. Cosplayers often interact to create a subculture, ...
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 any pigmented liquid, liquefiable, or solid mastic composition that, after application to a substrate in a thin layer, converts to a solid film. It is most commonly used to protect, color, or provide texture. Paint can be made in many ...
s at 53% primary dispersant.
Hydrolysis of EVA gives ethylene vinyl alcohol (EVOH) copolymer.
Other uses
EVA is used in orthotics, surfboard and skimboard traction pads, car mats and for the manufacturing of some artificial flowers. It is used as a cold flow improver for diesel fuel and as a separator in
HEPA filter
HEPA (, high-efficiency particulate air) filter, also known as high-efficiency particulate absorbing filter and high-efficiency particulate arrestance filter, is an efficiency standard of air filters.
Filters meeting the HEPA standard must s ...
s. EVA can easily be cut from sheets and molded to shape. It is also used to make thermoplastic mouthguards that soften in boiling water for a user-specific fit. It is also used for conditioning and waterproofing leather.
EVA finds application in the making of nicotine transdermal patches, 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.
Safety and environmental considerations
Polyethylene vinyl acetate has recently become a popular alternative to polyvinyl chloride because it does not contain chlorine. As of 2014, EVA has not been found to be carcinogenic by the NTP, ACGIH, IARC or OSHA, 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 living organisms, but its effect on humans has not been determined.