Polyvinyl alcohol is a
waterWater is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
-soluble
synthetic polymerSynthetic polymers are often referred to as "plastics", such as the well-known polyethylene and nylon. However, most of them can be classified in at least three main categories: thermoplastics, thermosets and elastomers....
(not to be confused with
polyvinyl acetatePolyvinyl acetate, PVA, PVAc, poly, is a rubbery synthetic polymer with the formula n. It belongs to the polyvinyl esters family with the general formula -[RCOOCHCH2]-...
, a popular wood glue).
Properties
Polyvinyl alcohol has excellent film forming,
emulsifyingAn emulsion is a mixture of two or more liquids that are normally immiscible . Emulsions are part of a more general class of two-phase systems of matter called colloids. Although the terms colloid and emulsion are sometimes used interchangeably, emulsion is used when both the dispersed and the...
and
adhesiveAdhesion is any attraction process between dissimilar molecular species that can potentially bring them in close contact. By contrast, cohesion takes place between similar molecules....
properties. It is also resistant to oil, grease and
solventA solvent is a liquid, solid, or gas that dissolves another solid, liquid, or gaseous solute, resulting in a solution that is soluble in a certain volume of solvent at a specified temperature...
. It is odorless and nontoxic. It has high tensile strength and flexibility, as well as high oxygen and aroma barrier properties. However these properties are dependent on
humidityHumidity is a term for the amount of water vapor in the air, and can refer to any one of several measurements of humidity. Formally, humid air is not "moist air" but a mixture of water vapor and other constituents of air, and humidity is defined in terms of the water content of this mixture,...
, in other words, with higher humidity more water is absorbed. The water, which acts as a plasticiser, will then reduce its tensile strength, but increase its elongation and tear strength.
PVA is fully degradable and dissolves quickly. PVA has a melting point of 230°C and 180–190°C(356-374 degrees Fahrenheit) for the fully hydrolysed and partially hydrolysed grades, respectively. It decomposes rapidly above 200°C as it can undergo
pyrolysisPyrolysis is a thermochemical decomposition of organic material at elevated temperatures without the participation of oxygen. It involves the simultaneous change of chemical composition and physical phase, and is irreversible...
at high temperatures.
PVA is an atactic material but exhibits
crystalA crystal or crystalline solid is a solid material whose constituent atoms, molecules, or ions are arranged in an orderly repeating pattern extending in all three spatial dimensions. The scientific study of crystals and crystal formation is known as crystallography...
linity as the
hydroxylA hydroxyl is a chemical group containing an oxygen atom covalently bonded with a hydrogen atom. In inorganic chemistry, the hydroxyl group is known as the hydroxide ion, and scientists and reference works generally use these different terms though they refer to the same chemical structure in...
groups are small enough to fit into the lattice without disrupting it.
PVA is close to incompressible. The
Poisson's ratioPoisson's ratio , named after Siméon Poisson, is the ratio, when a sample object is stretched, of the contraction or transverse strain , to the extension or axial strain ....
has been measured to between 0.42 and 0.48.
Uses
Polyvinyl alcohol is the raw material to make other polymers like:
- Polyvinyl nitrate
Polyvinyl nitrate is a polymeric explosive material, an ester of nitric acid and polyvinyl alcohol. It is prepared by nitration of polyvinyl alcohol or transesterification of polyvinyl acetate...
(PVN): It is an esterEsters are chemical compounds derived by reacting an oxoacid with a hydroxyl compound such as an alcohol or phenol. Esters are usually derived from an inorganic acid or organic acid in which at least one -OH group is replaced by an -O-alkyl group, and most commonly from carboxylic acids and...
of nitric acidNitric acid , also known as aqua fortis and spirit of nitre, is a highly corrosive and toxic strong acid.Colorless when pure, older samples tend to acquire a yellow cast due to the accumulation of oxides of nitrogen. If the solution contains more than 86% nitric acid, it is referred to as fuming...
and polyvinyl alcohol.
- Polyvinyl acetal
An acetal is a molecule with two single-bonded oxygen atoms attached to the same carbon atom.Traditional usages distinguish ketals from acetals...
s: Polyvinyl acetals are prepared by reacting aldehydeAn aldehyde is an organic compound containing a formyl group. This functional group, with the structure R-CHO, consists of a carbonyl center bonded to hydrogen and an R group....
s with polyvinyl alcohol. Polyvinyl butyralPolyvinyl butyral is a resin usually used for applications that require strong binding, optical clarity, adhesion to many surfaces, toughness and flexibility. It is prepared from polyvinyl alcohol by reaction with butyraldehyde. The major application is laminated safety glass for automobile...
(PVB) and polyvinyl formal (PVF) are examples of this family of polymers. They are prepared from polyvinyl alcohol by reaction with butyraldehyde and formaldehydeFormaldehyde is an organic compound with the formula CH2O. It is the simplest aldehyde, hence its systematic name methanal.Formaldehyde is a colorless gas with a characteristic pungent odor. It is an important precursor to many other chemical compounds, especially for polymers...
, respectively. Preparation of polyvinyl butyral is the largest use for polyvinyl alcohol in the U.S. and Western Europe.
Polyvinyl alcohol is used as a
emulsion polymerizationEmulsion polymerization is a type of radical polymerization that usually starts with an emulsion incorporating water, monomer, and surfactant. The most common type of emulsion polymerization is an oil-in-water emulsion, in which droplets of monomer are emulsified in a continuous phase of water...
aid, as protective colloid, to make
polyvinyl acetatePolyvinyl acetate, PVA, PVAc, poly, is a rubbery synthetic polymer with the formula n. It belongs to the polyvinyl esters family with the general formula -[RCOOCHCH2]-...
dispersions. This is the largest market application in China.
In Japan its major use is vinylon fiber production.
Some other uses of polyvinyl alcohol include:
- Paper adhesive with boric acid
Boric acid, also called hydrogen borate or boracic acid or orthoboric acid or acidum boricum, is a weak acid of boron often used as an antiseptic, insecticide, flame retardant, as a neutron absorber, and as a precursor of other chemical compounds. It exists in the form of colorless crystals or a...
in spiral tube winding and solid board production
- Thickener, modifier, in polyvinyl acetate
Polyvinyl acetate, PVA, PVAc, poly, is a rubbery synthetic polymer with the formula n. It belongs to the polyvinyl esters family with the general formula -[RCOOCHCH2]-...
glues
- Textile sizing
Sizing or size is any one of numerous specific substances that is applied to or incorporated in other material, especially papers and textiles, to act as a protecting filler or glaze....
agent
- Paper coatings
Coated paper is paper which has been coated by a compound to impart certain qualities to the paper, including weight, surface gloss, smoothness or reduced ink absorbency. Kaolinite or calcium carbonate are used to coat paper for high quality printing used in packaging industry and in magazines...
, release linerA Release liner is a paper or plastic based carrier web material, which is coated on one or two sides with a release agent, which provides a release effect against any type of a sticky material such as an adhesive or a mastic. Release liner are available in different colors, with or without...
,
- As a water-soluble film useful for packaging. An example is the envelope containing laundry detergent in "liqui-tabs".
- Feminine hygiene and adult incontinence products as a biodegradable plastic backing sheet.
- Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
barrier in polyethylene terephthalatePolyethylene terephthalate , commonly abbreviated PET, PETE, or the obsolete PETP or PET-P, is a thermoplastic polymer resin of the polyester family and is used in synthetic fibers; beverage, food and other liquid containers; thermoforming applications; and engineering resins often in combination...
(PET) bottles
- As a film used in the water transfer printing
Hydrographics or HydroGraphics, also known as immersion printing, water transfer printing, water transfer imaging or cubic printing, is a method of applying printed designs to three-dimensional objects. The hydrographic process can be used on metal, plastic, glass, hard woods, and various other...
process
- As a mold release because materials such as epoxy
Epoxy, also known as polyepoxide, is a thermosetting polymer formed from reaction of an epoxide "resin" with polyamine "hardener". Epoxy has a wide range of applications, including fiber-reinforced plastic materials and general purpose adhesives....
do not stick to it
- Movie practical effect
A practical effect is a special effect in which a prop appears to work in a situation where it obviously could not in real life . They do not use trick photography or post-production artifice. This type of effect is normally found in live theatre.In film, practical effect denotes an effect produced...
and children's play puttyPutty is a generic term for a plastic material similar in texture to clay or dough typically used in domestic construction and repair as a sealant or filler. Painter's Putty is typically a linseed oil based product used for filling holes, minor cracks and defacements in wood only...
or slime when combined with boraxBorax, also known as sodium borate, sodium tetraborate, or disodium tetraborate, is an important boron compound, a mineral, and a salt of boric acid. It is usually a white powder consisting of soft colorless crystals that dissolve easily in water.Borax has a wide variety of uses...
- Used in eye drops and hard contact lens
A contact lens, or simply contact, is a lens placed on the eye. They are considered medical devices and can be worn to correct vision, for cosmetic or therapeutic reasons. In 2004, it was estimated that 125 million people use contact lenses worldwide, including 28 to 38 million in the United...
solution as a lubricant
- PVA fiber, as reinforcement in concrete
- As a surfactant for the formation of polymer encapsulated nanobeads
- Used in protective chemical-resistant gloves
- Used as a fixative
A fixative is a stabilizing or preservative agent:*Fixative , a liquid usually sprayed over a finished piece of artwork to better preserve it and prevent smudging...
for specimen collection, especially stool samples
- When doped with iodine, PVA can be used to polarize light
- As an embolization
Embolization is a non-surgical, minimally-invasive procedure performed by an interventional radiologist and interventional neuroradiologists. It involves the selective occlusion of blood vessels by purposely introducing emboli.-Therapeutic applications:...
agent in medical procedures
- Carotid phantoms for use as synthetic vessels in Doppler
Doppler echocardiography is a procedure which uses ultrasound technology to examine the heart. An echocardiogram uses high frequency sound waves to create an image of the heart while the use of Doppler technology allows determination the speed and direction of blood flow by utilizing the Doppler...
flow testing
- As agent in artificial Tears for treatment of dry eye.
- See more specific polyvinyl alcohol uses
The
North KoreaThe Democratic People’s Republic of Korea , , is a country in East Asia, occupying the northern half of the Korean Peninsula. Its capital and largest city is Pyongyang. The Korean Demilitarized Zone serves as the buffer zone between North Korea and South Korea...
n-manufacture fiber
VinalonVinylon is a synthetic fiber produced from polyvinyl alcohol, using anthracite and limestone as raw materials. Vinalon was first developed in 1939 by Japanese scientist, Ichiro Sakurada, Yi Sung-ki [Lee. S.or Ri.Sung.Gi.] and H. Kawakami Production of this fiber was delayed for World War II. The...
is produced from polyvinyl alcohol. Despite its inferior properties as a clothing fiber, it is produced for self-sufficiency reasons, because no
oilPetroleum or crude oil is a naturally occurring, flammable liquid consisting of a complex mixture of hydrocarbons of various molecular weights and other liquid organic compounds, that are found in geologic formations beneath the Earth's surface. Petroleum is recovered mostly through oil drilling...
is required to produce it.
Fishing
PVA is widely used in
freshwaterFresh water is naturally occurring water on the Earth's surface in ice sheets, ice caps, glaciers, bogs, ponds, lakes, rivers and streams, and underground as groundwater in aquifers and underground streams. Fresh water is generally characterized by having low concentrations of dissolved salts and...
sport fishing. Small bags made from PVA are filled with dry or oil based
baitFishing bait is any substance used to attract and catch fish, e.g. on the end of a fishing hook, or inside a fish trap. Traditionally, nightcrawlers, insects, and smaller bait fish have been used for this purpose...
and attached to the hook, or the baited hook is placed inside the bag and cast into the water. When the bag lands on the
lakeA lake is a body of relatively still fresh or salt water of considerable size, localized in a basin, that is surrounded by land. Lakes are inland and not part of the ocean and therefore are distinct from lagoons, and are larger and deeper than ponds. Lakes can be contrasted with rivers or streams,...
or
riverA river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...
bottom it breaks down, leaving the
hookA fish hook is a device for catching fish either by impaling them in the mouth or, more rarely, by snagging the body of the fish. Fish hooks have been employed for centuries by fishermen to catch fresh and saltwater fish. In 2005, the fish hook was chosen by Forbes as one of the top twenty tools...
bait surrounded by ground bait, pellets etc. This method helps attract
fishFish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
to the hook bait.
AnglerAngling is a method of fishing by means of an "angle" . The hook is usually attached to a fishing line and the line is often attached to a fishing rod. Fishing rods are usually fitted with a fishing reel that functions as a mechanism for storing, retrieving and paying out the line. The hook itself...
s also use string made of PVA for the purpose of making temporary attachments. For example, holding a length of line in a
coilA coil is a series of loops. A coiled coil is a structure in which the coil itself is in turn also looping.-Electromagnetic coils:An electromagnetic coil is formed when a conductor is wound around a core or form to create an inductor or electromagnet...
, that might otherwise tangle while the cast is made.
Production
Consumption of polyvinyl alcohol was over one million metric tons in 2006. Larger producers include
Kurarayis a Japanese manufacturer of chemicals, fibers and other materials founded in Kurashiki, Okayama, but based in Otemachi, Chiyoda, Tokyo and Umeda, Kita-ku, Osaka . , Kuraray was the sole worldwide producer of Vectran liquid crystal polymer fibre....
(Japan and Europe) and Sekisui Specialty Chemicals (USA) but mainland China has installed a number of very large production facilities in the past decade and currently accounts for 45% of world capacity.
Preparation
Unlike many
vinylA vinyl compound is any organic compound that contains a vinyl group ,which are derivatives of ethene, CH2=CH2, with one hydrogen atom replaced with some other group...
polymers, PVA is not prepared by polymerization of the corresponding
monomerA monomer is an atom or a small molecule that may bind chemically to other monomers to form a polymer; the term "monomeric protein" may also be used to describe one of the proteins making up a multiprotein complex...
. The monomer,
vinyl alcoholVinyl alcohol, also called ethenol , is an alcohol. It is not to be confused with the drinking alcohol, ethanol. With the formula 2CHH, vinyl alcohol is an isomer of acetaldehyde and ethylene oxide...
, almost exclusively exists as the
tautomerTautomers are isomers of organic compounds that readily interconvert by a chemical reaction called tautomerization. This reaction commonly results in the formal migration of a hydrogen atom or proton, accompanied by a switch of a single bond and adjacent double bond...
ic form,
acetaldehydeAcetaldehyde is an organic chemical compound with the formula CH3CHO or MeCHO. It is one of the most important aldehydes, occurring widely in nature and being produced on a large scale industrially. Acetaldehyde occurs naturally in coffee, bread, and ripe fruit, and is produced by plants as part...
. PVA instead is prepared by partial or complete
hydrolysisHydrolysis is a chemical reaction during which molecules of water are split into hydrogen cations and hydroxide anions in the process of a chemical mechanism. It is the type of reaction that is used to break down certain polymers, especially those made by condensation polymerization...
(sometimes referred to in this case as
saponificationSaponification is a process that produces soap, usually from fats and lye. In technical terms, saponification involves base hydrolysis of triglycerides, which are esters of fatty acids, to form the sodium salt of a carboxylate. In addition to soap, such traditional saponification processes...
) of
polyvinyl acetatePolyvinyl acetate, PVA, PVAc, poly, is a rubbery synthetic polymer with the formula n. It belongs to the polyvinyl esters family with the general formula -[RCOOCHCH2]-...
to remove
acetateAn acetate is a derivative of acetic acid. This term includes salts and esters, as well as the anion found in solution. Most of the approximately 5 billion kilograms of acetic acid produced annually in industry are used in the production of acetates, which usually take the form of polymers. In...
groups.
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