Polyvinyl alcohol

This article needs additional citations for verification. Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (August 2007)

Polyvinyl alcohol
Other names	PVOH; Ethenol, homopolymer; PVA; Polyviol; Vinol; Alvyl; Alkotex; Covol; Gelvatol; Lemol; Mowiol
Identifiers
CAS number	9002-89-5 Y
RTECS number	TR8100000
Properties
Molecular formula	(C2H4O)x
Density	1.19-1.31 g/cm³
Melting point	230°C
Boiling point	228°C
Hazards
MSDS	External MSDS
NFPA 704	0 1 0
Flash point	79.44°C
LD50	14,700 mg/kg (Mouse)
Y (what is this?)  (verify) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Polyvinyl alcohol (PVOH, PVA, or PVAL) is a water-soluble synthetic polymer (not to be confused with polyvinyl acetate, a popular wood glue).

Properties

Polyvinyl alcohol has excellent film forming, emulsifying, and adhesive properties. It is also resistant to oil, grease and solvent. 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, 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, respectively. It decomposes rapidly above 200°C as it can undergo pyrolysis at high temperatures.

PVA is an atactic material but exhibits crystallinity as the hydroxyl groups are small enough to fit into the lattice without disrupting it.

Uses

Preparation of polyvinyl butyral 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.^[1]

Some other uses of polyvinyl alcohol include:

1. Adhesive and thickener material in latex paints, paper coatings, release liner, hairsprays, shampoos and glues.
2. Textile sizing agent
3. Carbon dioxide barrier in polyethylene terephthalate (PET) bottles
4. Carotid phantoms for use as synthetic vessels in doppler flow testing
5. Movie practical effect and children's play putty or slime when combined with borax
6. Feminine hygiene and adult incontinence products as a biodegradable plastic backing sheet.
7. As a mold release because materials such as epoxy do not stick to it
8. As a water-soluble film useful for packaging.
9. As fiber reinforcement in concrete
10. As a surfactant for the formation of polymer encapsulated nanobeads
11. Used with polyvinyl acetate to make Elmer's glue
12. Used in eye drops and hard contact lens solution as a lubricant
13. Used in protective chemical-resistant gloves
14. Used as a fixative for specimen collection, especially stool samples
15. When doped with iodine, PVA can be used to polarize light
16. As an embolization agent in medical procedures
17. As a film used in the water transfer printing process

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.^[1] Larger producers include Kuraray (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 capactity.

Preparation

Unlike most vinyl polymers, PVA is not prepared by polymerization of the corresponding monomer. The monomer, vinyl alcohol, almost exclusively exists as the tautomeric form, acetaldehyde. PVA instead is prepared by partial or complete hydrolysis of polyvinyl acetate to remove acetate groups.

See also

• Polyvinyl acetate
• Vinyl acetate
• Polymerization

References

1. ^ ^{a b} SRI Consulting CEH Report Polyvinyl Alcohol, published March 2007, abstract retrieved July 30, 2008.

External links

• MSDS
• Listed as a plastic by the Society of the Plastics Industry
• "Slime" recipe
• Forming PVA layers in PET bottles
• An Introduction to PVA for Carp Fishing