Polyvinyl_alcohol Knowpia

Polyvinyl alcohol
Names
	Other names PVOH; Poly(Ethenol), Ethenol, homopolymer; PVA; Polyviol; Vinol; Alvyl; Alcotex; Covol; Gelvatol; Lemol; Mowiol; Mowiflex, Alcotex, Elvanol, Gelvatol, Lemol, Mowiol, Nelfilcon A, Polyviol und Rhodoviol
Identifiers
CAS Number	9002-89-5 ;
ChEMBL	ChEMBL76101 ;
ChemSpider	none;
ECHA InfoCard	100.121.648
E number	E1203 (additional chemicals)
KEGG	C00980 ;
RTECS number	TR8100000;
UNII	1E30GE2EF7 ;
CompTox Dashboard (EPA)	DTXSID4031930 ;
Properties
Chemical formula	(C2H4O)x
Density	1.19–1.31 g/cm3
Melting point	200 °C (392 °F; 473 K)
log P	0.26
Refractive index (nD)	1.477 @ 632 nm
Hazards
NFPA 704 (fire diamond)	0 0 0
Flash point	79.44 °C (174.99 °F; 352.59 K)
	Lethal dose or concentration (LD, LC):
LD50 (median dose)	14,700 mg/kg (mouse)
Safety data sheet (SDS)	External MSDS
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). verify (what is ?) Infobox references

Poly(vinyl alcohol) (PVOH, PVA, or PVAl) is a water-soluble synthetic polymer. It has the idealized formula [CH₂CH(OH)]_n. It is used in papermaking, textile warp sizing, as a thickener and emulsion stabilizer in polyvinyl acetate (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.^[3]^[4] Without an externally added crosslinking agent, PVA solution can be gelled through repeated freezing-thawing, yielding highly strong, ultrapure, biocompatible hydrogels which have been used for a variety of applications such as vascular stents, cartilages, contact lenses, etc.^[5]

UsesEdit

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 drops.^[6] 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 fiber.^[7] This fiber is also manufactured in North Korea for self-sufficiency reasons, because no oil is required to produce it. Another application is photographic film.^[8]

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.^[9]

Medically, it may also used as the embolic agent in a Uterine Fibroid Embolectomy (UFE).^[10]

PVA is commonly used in household sponges that absorb more water than Polyurethane sponges. PVA glue is commonly used for glueing porous materials like wood, paper and cloth.

Polyvinyl acetalsEdit

Polyvinyl acetals are prepared by treating PVA with aldehydes. Butyraldehyde and formaldehyde afford polyvinyl butyral (PVB) and polyvinyl formal (PVF), respectively. Preparation of polyvinyl butyral is the largest use for polyvinyl alcohol in the US and Western Europe.

PreparationEdit

Unlike most vinyl polymers, PVA is not prepared by polymerization of the corresponding monomer, since the monomer, vinyl alcohol, is thermodynamically unstable with respect to its tautomerization to acetaldehyde. Instead, PVA is prepared by hydrolysis of polyvinyl acetate,^[3] or sometimes other vinyl ester-derived polymers with formate or chloroacetate groups instead of acetate. The conversion of the polyvinyl esters is usually conducted by base-catalysed transesterification with ethanol:

[CH₂CH(OAc)]_n + C₂H₅OH → [CH₂CH(OH)]_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.^[7] Large producers include Kuraray and Sekisui Specialty Chemicals, while mainland China has installed a number of very large production facilities in the past decade^{[clarification needed]} and currently accounts for 45% of world capacity.

Structure and propertiesEdit

PVA is an atactic material that exhibits crystallinity. 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.^[3]

Polyvinyl alcohol has excellent film-forming, emulsifying and adhesive properties. It is also resistant to oil, grease and solvents. It has high tensile strength and flexibility, as well as high oxygen and aroma barrier properties. However, these properties are dependent on humidity: water absorbed at higher humidity levels acts as a plasticiser, which reduces the polymer's tensile strength, but increases its elongation and tear strength.

Safety and environmental considerationsEdit

PVA is widely used, thus its toxicity and biodegradation are of interest. Solutions containing more than 5% PVA are toxic to fish.^[3] It biodegrades slowly.^[11]

ReferencesEdit

^ "Poly(vinyl alcohol)". ChemSrc.
^ Schnepf MJ, Mayer M, Kuttner C, et al. (July 2017). "Nanorattles with tailored electric field enhancement". Nanoscale. 9 (27): 9376–9385. doi:10.1039/C7NR02952G. PMID 28656183.
^ ^a ^b ^c ^d Hallensleben ML (2000). "Polyvinyl Compounds, Others". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a21_743.
^ Tang X, Alavi S (2011). "Recent Advances in Starch, Polyvinyl Alcohol Based Polymer Blends, Nanocomposites and Their Biodegradability". Carbohydrate Polymers. 85: 7–16. doi:10.1016/j.carbpol.2011.01.030.
^ Adelnia, Hossein; Ensandoost, Reza; Shebbrin Moonshi, Shehzahdi; et al. (2022-02-05). "Freeze/thawed polyvinyl alcohol hydrogels: Present, past and future". European Polymer Journal. 164: 110974. doi:10.1016/j.eurpolymj.2021.110974. ISSN 0014-3057. S2CID 245576810.
^ Baker MI, Walsh SP, Schwartz Z, Boyan BD (July 2012). "A review of polyvinyl alcohol and its uses in cartilage and orthopedic applications". Journal of Biomedical Materials Research Part B: Applied Biomaterials. 100 (5): 1451–7. doi:10.1002/jbm.b.32694. PMID 22514196.
^ ^a ^b SRI Consulting CEH Report Polyvinyl Alcohol, published March 2007, abstract retrieved July 30, 2008.
^ Lampman, Steve, ed. (2003). "Effects of Composition, Processing, and Structure on Properties of Engineering Plastics". Characterization and Failure Analysis of Plastics. ASM International. p. 29. doi:10.31399/asm.tb.cfap.t69780028. ISBN 978-0-87170-789-5.
^ Xu X, Zhao J, Wang M, et al. (August 2019). "3D Printed Polyvinyl Alcohol Tablets with Multiple Release Profiles". Scientific Reports. 9 (1): 12487. doi:10.1038/s41598-019-48921-8. PMC 6713737. PMID 31462744.
^ Siskin GP. Cho KJ (ed.). "Uterine Fibroid Embolization and Imaging". Medscape. WebMD LLC. Archived from the original on 2015-03-04.
^ Kawai F, Hu X (August 2009). "Biochemistry of microbial polyvinyl alcohol degradation". Applied Microbiology and Biotechnology. 84 (2): 227–37. doi:10.1007/s00253-009-2113-6. PMID 19590867. S2CID 25068302.