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Polyvinyl alcohol
Other names	PVOH; Ethenol, homopolymer; PVA; Polyviol; Vinol; Alvyl; Alkotex; Covol; Gelvatol; Lemol;
Identifiers
CAS number	9002-89-5
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	2 0 0
Flash point	79.44°C
LD50	14,700 mg/kg (Mouse)
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.

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

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, though it does result in dissolved plastic in the water.

Anglers also use string made of PVA for the purpose of making temporary attachments; for example holding in a coil a length of line that might otherwise tangle while the cast is made.

Production

Consumption of polyvinyl alcohol was over one million metric tons in 2006.² Larger producers include Kuraray (Japan) 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 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.

References

1. ^ SRI Consulting CEH Report Polyvinyl Alcohol, published March 2007, abstract retrieved July 30, 2008.
2. ^ 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

Wikipedia content modification information:

• This page was last modified on 12 November 2008, at 19:03.

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