Polyvinyl alcohol

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Polyvinyl alcohol

Polyvinyl alcohol (PVOH, PVA, or PVAL) is a water

Water

Water is a common chemical substance that is essential for the survival of all known forms of life. In typical usage, water refers only to its liquid form or States of matter, but the substance also has a solid state, ice, and a gaseous state, water vapor or steam....
-soluble synthetic polymer

Synthetic polymer

Synthetic 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....
.

vinyl alcohol has excellent film forming, emulsifying

Emulsion

An emulsion is a mixture of two immiscible liquids. One liquid is dispersion in the other . Many emulsions are oil/water emulsions, with dietary fats being one common type of oil encountered in everyday life....
, and adhesive

Adhesion

Adhesion is the tendency of certain dissimilar molecules to cling together due to attractive forces....
properties. It is also resistant to oil, grease and solvent

Solvent

A solvent is a liquid or gas that dissolves a solid, liquid, or gaseous solute, resulting in a solution.The most common solvent in everyday life is water....
. 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 humidity

Humidity

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Properties

Polyvinyl alcohol has excellent film forming, emulsifying

Emulsion

Adhesion

Adhesion is the tendency of certain dissimilar molecules to cling together due to attractive forces....
properties. It is also resistant to oil, grease and solvent

Solvent

Humidity

Humidity is the amount of water vapor in the air. In daily language the term "humidity" is normally taken to mean relative humidity. Relative humidity is defined as the ratio of the partial pressure of water vapor in a Air parcel of air to the saturated vapor pressure of water vapor at a prescribed temperature....
, 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 is a quick dissolver. PVA has a melting point of 230°C and 180–190°C for the fully hydrolysed and partially hydrolysed grades. It decomposes rapidly above 200°C as it can undergo pyrolysis

Pyrolysis

Pyrolysis is the chemical decomposition of a condensed substance by heating. The word is coined from the Greek language-derived morphemes pyro "fire" and lysys "decomposition"....
at high temperatures.

PVA is an atactic material but exhibits crystal

Crystal

A 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....
linity as the hydroxyl

Hydroxyl

Hydroxyl in chemistry stands for a molecule consisting of an oxygen atom and a hydrogen atom connected by a covalent bond. The neutral form is a hydroxyl Radical and the hydroxyl anion is called a hydroxide....
groups are small enough to fit into the lattice without disrupting it.

Uses

Preparation of polyvinyl butyral

Polyvinyl butyral

Polyvinyl butyral is a resin usually used for applications that require strong binding, optical clarity, adhesion to many surfaces, toughness and flexibility....
is the largest use for polyvinyl alcohol in the U.S. and western Europe. Its use as a polymerization aid is the largest market in China. In Japan the major use is vinylon fiber production.

Some other uses of polyvinyl alcohol include:

Adhesive and thickener material in latex paints, paper coatings, hairsprays, shampoos and glues.
Textile sizing
Sizing

Sizing or size is a substance that is applied to materials as a protecting glaze, filler, or lubricant. It is used to change surface properties in papermaking, gilding, and the manufacture of textiles and fiberglass....
agent
Carbon dioxide
Carbon dioxide

Carbon dioxide is a chemical compound composed of two oxygen atoms covalent bond to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state....
barrier in polyethylene terephthalate
Polyethylene terephthalate

Polyethylene tephthalate , 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 Packaging; thermoforming applications; and engineering resins often in combination with glass fiber....
(PET) bottles.
Carotid phantoms for use as synthetic vessels in doppler
Doppler

Doppler can refer to:...
flow testing.
Movie practical effect
Practical effect

A practical special effect is one in which a Theatrical property object appears to work in a situation where it obviously could not . No trick photography or post-production editing is involved....
and children's play putty
PuTTY

PuTTY is a terminal emulator application which can act as a client for the Secure Shell, Telnet, rlogin, and Transmission Control Protocol computing protocols....
or slime when combined with borax
Borax

Borax, also known as sodium borate, sodium tetraborate, or disodium tetraborate, is an important boron compound, a mineral, and a salt of boric acid....
.
Feminine hygiene and adult incontinence products as a biodegradable plastic backing sheet.
As a mold release because materials such as epoxy
Epoxy

In chemistry, epoxy or polyepoxide is a thermosetting epoxide polymer that cures when mixed with a catalyst agent or hardener. Most common epoxy resins are produced from a reaction between epichlorohydrin and bisphenol-A....
do not stick to it.
As a water-soluble film useful for packaging.
As fiber reinforcement in concrete
As a surfactant for the formation of polymer encapsulated nanobeads
Used with polyvinyl acetate to make Elmer's glue
Used in eye drops and hard contact lens
Contact lens

A contact lens is a corrective lens, cosmetics, or therapeutic lens usually placed on the cornea of the eye. Modern soft contact lenses were invented by the Czech Republic chemists Otto Wichterle and Drahoslav L?m, who also invented the first gel used for their production....
solution as a lubricant.
Used in protective chemical-resistant gloves
Used as a fixative
Fixative

A fixative is a stabilizing or preservative agent:*Fixative *Fixation , a solution used to preserve or harden fresh tissue of cell specimens for microscopic examination....
for specimen collection, especially stool samples
When doped with iodine, PVA can be used to polarize light.
As an embolization
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....
agent in medical procedures

Fishing

PVA is widely used in freshwater sport fishing. Small bags made from PVA are filled with dry- or oil-based bait 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 lake or river bottom it breaks down, leaving the hook bait surrounded by ground bait, pellets etc. This method helps attract fish to the hook bait.

Anglers also use string made of PVA for the purpose of making temporary attachments. For example, holding a length of line in a coil, 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 Kuraray (Japan and Europe) and Celanese (USA) but mainland China has installed a number of very large production facilities in the past decade and currently accounts for 45% of world capactity.

Preparation

Unlike most vinyl

Vinyl

A vinyl compound is any organic compound that contains a vinyl group , −CarbonHydrogenCovalent bondCH2. These 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 monomer

Monomer

A monomer is a small molecule that may become Chemistry chemical bonding to other monomers to form a polymer....
. The monomer, vinyl alcohol

Ethenol

Ethenol, also called vinyl alcohol, hydroxyethene or hydroxyethylene, is an alcohol with chemical formula 23 and CAS number 557-75-5....
, almost exclusively exists as the tautomer

Tautomer

Tautomers are isomers of organic compounds that readily interconvert by a chemical reaction called tautomerization. Commonly this reaction 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, acetaldehyde

Acetaldehyde

Acetaldehyde is an organic compound with the chemical formula CarbonHydrogen3CHOxygen or MeCHO. It is a flammable liquid with a fruity smell....
. PVA instead is prepared by partial or complete hydrolysis

Hydrolysis

Hydrolysis is a chemical reaction during which one or more water are split into hydrogen and hydroxide ions which may go on to participate in further reactions....
of polyvinyl acetate

Polyvinyl acetate

Polyvinyl acetate is a rubbery synthetic polymer. PVA is a common copolymer.It is prepared by polymerization of vinyl acetate, also referred to as VAM....
to remove acetate

Acetate

An acetate, or ethanoate, is either a salt or ester of acetic acid.In chemistry, the abbreviation Ac refers to the acetyl group. The anion and the functional group may be written as -OAc and AcO-, or OAc respectively....
groups.

Polyvinyl alcohol

Properties

Uses

Fishing

Production

Preparation

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