Poly(vinyl alcohol) (PVOH, PVA, or PVAl) is a

water Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as a ...

soluble In chemistry, solubility is the ability of a substance, the solute, to form a solution with another substance, the solvent. Insolubility is the opposite property, the inability of the solute to form such a solution. The extent of the solubi ...

synthetic polymer. It has the idealized formula H₂CH(OH)sub>''n''. It is used in papermaking,

textile warp sizing Sizing or size is a substance that is applied to, or incorporated into, other materials—especially papers and textiles—to act as a protective filler or glaze. Sizing is used in papermaking and textile manufacturing to change the absorption ...

, as a thickener and emulsion stabilizer in

polyvinyl acetate Polyvinyl acetate (PVA, PVAc, poly(ethenyl ethanoate)), commonly known as wood glue, PVA glue, white glue, carpenter's glue, school glue, or Elmer's glue in the US, is a widely available adhesive used for porous materials like wood, paper, and ...

(PVAc) adhesive formulations, in a variety of coatings, and 3D printing. It is colourless (white) and odorless. It is commonly supplied as beads or as solutions in water. Without an externally added crosslinking agent, PVA solution can be gelled through repeated freezing-thawing, yielding highly strong, ultrapure,

biocompatible Biocompatibility is related to the behavior of biomaterials in various contexts. The term refers to the ability of a material to perform with an appropriate host response in a specific situation. The ambiguity of the term reflects the ongoing de ...

hydrogels which have been used for a variety of applications such as vascular stents, cartilages, contact lenses, etc.

Uses

PVA is used in a variety of medical applications because of its biocompatibility, low tendency for protein adhesion, and low toxicity. Specific uses include cartilage replacements, contact lenses, and

eye drop Eye drops or eyedrops are liquid drops applied directly to the surface of the eye usually in small amounts such as a single drop or a few drops. Eye drops usually contain saline to match the salinity of the eye. Drops containing only saline ...

s. Polyvinyl alcohol is used as an aid in suspension polymerizations. Its largest application in China is its use as a protective colloid to make PVAc dispersions. In Japan its major use is the production of

Vinylon Vinylon, also known as Vinalon, is a synthetic fiber produced from polyvinyl alcohol, using anthracite and limestone as raw materials. Vinylon was first developed in Japan in 1939 by Ri Sung-gi, Ichiro Sakurada, and H. Kawakami. Trial production ...

fiber.SRI Consulting CEH Report Polyvinyl Alcohol
published March 2007, abstract retrieved July 30, 2008. This fiber is also manufactured in

North Korea North Korea, officially the Democratic People's Republic of Korea (DPRK), is a country in East Asia. It constitutes the northern half of the Korea, Korean Peninsula and shares borders with China and Russia to the north, at the Yalu River, Y ...

for self-sufficiency reasons, because no

oil An oil is any nonpolar chemical substance that is composed primarily of hydrocarbons and is hydrophobic (does not mix with water) & lipophilic (mixes with other oils). Oils are usually flammable and surface active. Most oils are unsaturated ...

is required to produce it. Another application is photographic film. PVA-based polymers are used widely in additive manufacturing. For example, 3D printed oral dosage forms demonstrate great potential in the pharmaceutical industry. It is possible to create drug-loaded tablets with modified drug-release characteristics where PVA is used as a binder substance. Medically, it may also used as the embolic agent in a Uterine Fibroid Embolectomy (UFE). PVA is commonly used in household sponges that absorb more water than

Polyurethane Polyurethane (; often abbreviated PUR and PU) refers to a class of polymers composed of organic units joined by carbamate (urethane) links. In contrast to other common polymers such as polyethylene and polystyrene, polyurethane is produced from ...

sponges. PVA glue is commonly used for glueing porous materials like wood, paper and cloth.

Polyvinyl acetals

Polyvinyl

acetals 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 no ...

are prepared by treating PVA with

aldehyde In organic chemistry, an aldehyde () is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred to as an aldehyde but can also be classified as a formyl grou ...

Butyraldehyde Butyraldehyde, also known as butanal, is an organic compound with the formula CH3(CH2)2CHO. This compound is the aldehyde derivative of butane. It is a colorless flammable liquid with an unpleasant smell. It is miscible with most organic solvent ...

and

formaldehyde Formaldehyde ( , ) (systematic name methanal) is a naturally occurring organic compound with the formula and structure . The pure compound is a pungent, colourless gas that polymerises spontaneously into paraformaldehyde (refer to section ...

afford

polyvinyl butyral Polyvinyl butyral (or PVB) is a resin mostly 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 majo ...

(PVB) and

polyvinyl formal Formvar refers to any of several thermoplastic resins that are polyvinyl formals, which are polymers formed from polyvinyl alcohol and formaldehyde as copolymers with polyvinyl acetate. They are typically used as coatings, adhesives, and molding m ...

(PVF), respectively. Preparation of polyvinyl butyral is the largest use for polyvinyl alcohol in the US and Western Europe.

Preparation

Unlike most

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 ...

s, PVA is not prepared by

polymerization In polymer chemistry, polymerization (American English), or polymerisation (British English), is a process of reacting monomer molecules together in a chemical reaction to form polymer chains or three-dimensional networks. There are many fo ...

of the corresponding

monomer In chemistry, a monomer ( ; '' mono-'', "one" + ''-mer'', "part") is a molecule that can react together with other monomer molecules to form a larger polymer chain or three-dimensional network in a process called polymerization. Classification ...

, since the monomer,

vinyl alcohol Vinyl alcohol, also called ethenol (IUPAC name; not ethanol), is the simplest enol. With the formula , it is a labile compound that converts to acetaldehyde. It is not a precursor to polyvinyl alcohol. Synthesis Vinyl alcohol can be formed by th ...

, is thermodynamically unstable with respect to its

tautomer Tautomers () are structural isomers (constitutional isomers) of chemical compounds that readily interconvert. The chemical reaction interconverting the two is called tautomerization. This conversion commonly results from the relocation of a hyd ...

ization to acetaldehyde. Instead, PVA is prepared by hydrolysis of polyvinyl acetate, or sometimes other vinyl ester-derived polymers with formate or

chloroacetate Chloroacetic acid, industrially known as monochloroacetic acid (MCA), is the organochlorine compound with the formula ClCH2CO2H. This carboxylic acid is a useful building block in organic synthesis. It is a colorless solid. Related compounds a ...

groups instead of acetate. The conversion of the polyvinyl esters is usually conducted by base-catalysed

transesterification In organic chemistry, transesterification is the process of exchanging the organic group R″ of an ester with the organic group R' of an alcohol. These reactions are often catalyzed by the addition of an acid or base catalyst. The reaction ca ...

with ethanol: : H₂CH(OAc)sub>''n'' + C₂H₅OH → H₂CH(OH)sub>''n'' + C₂H₅OAc The properties of the polymer are affected by the degree of transesterification. Worldwide consumption of polyvinyl alcohol was over one million metric tons in 2006. Large producers include

Kuraray is a Japanese manufacturer of chemicals, fibers and other materials. Their main manufacturing facilities are located in Kurashiki, Okayama. The company's Tokyo administrative offices are located in Otemachi, Chiyoda in the Ote Center Building ...

and Sekisui Specialty Chemicals, while mainland China has installed a number of very large production facilities in the past decade and currently accounts for 45% of world capacity.

Structure and properties

PVA is an

atactic Tacticity (from el, τακτικός, taktikos, "relating to arrangement or order") is the relative stereochemistry of adjacent chiral centers within a macromolecule. The practical significance of tacticity rests on the effects on the physical p ...

material that exhibits

crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macro ...

linity. In terms of microstructure, it is composed mainly of 1,3-diol linkages ��CH₂−CH(OH)−CH₂−CH(OH)− but a few percent of 1,2-diols ��CH₂−CH(OH)−CH(OH)−CH₂−occur, depending on the conditions for the polymerization of the vinyl ester precursor. Polyvinyl alcohol has excellent film-forming, emulsifying and

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 advant ...

properties. It is also resistant to oil, grease and

solvent A solvent (s) (from the Latin '' solvō'', "loosen, untie, solve") is a substance that dissolves a solute, resulting in a solution. A solvent is usually a liquid but can also be a solid, a gas, or a supercritical fluid. Water is a solvent for ...

s. It has high tensile strength and flexibility, as well as high oxygen and aroma barrier properties. However, these properties are dependent on

humidity Humidity is the concentration of water vapor present in the air. Water vapor, the gaseous state of water, is generally invisible to the human eye. Humidity indicates the likelihood for precipitation, dew, or fog to be present. Humidity dep ...

: water absorbed at higher humidity levels acts as a

plasticiser A plasticizer ( UK: plasticiser) is a substance that is added to a material to make it softer and more flexible, to increase its plasticity, to decrease its viscosity, and/or to decrease friction during its handling in manufacture. Plasticize ...

, which reduces the polymer's tensile strength, but increases its elongation and tear strength.

Safety and environmental considerations

PVA is widely used, thus its toxicity and biodegradation are of interest. Solutions containing more than 5% PVA are toxic to fish. It biodegrades slowly.

References

External links

MSDS
{{Authority control Vinyl polymers Biodegradable plastics Polymers E-number additives