Polyvinyl alcohol

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 PVAc adhesive formulations and a variety of coatings. It is colourless (white) and odorless. It is commonly supplied as beads or as solutions in water.[3][4]

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
ChEMBL
ChemSpider
  • none
ECHA InfoCard 100.121.648
E number E1203 (additional chemicals)
KEGG
RTECS number
  • TR8100000
Properties
(C2H4O)x
Density 1.19-1.31 g/cm3
Melting point 200 °C (392 °F; 473 K)
log P 0.26 [1]
1.477 @ 632 nm[2]
Hazards
Safety data sheet External MSDS
NFPA 704 (fire diamond)
Flammability code 0: Will not burn. E.g. waterHealth code 0: Exposure under fire conditions would offer no hazard beyond that of ordinary combustible material. E.g. sodium chlorideReactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
0
0
0
Flash point 79.44 °C (174.99 °F; 352.59 K)
Lethal dose or concentration (LD, LC):
14,700 mg/kg (Mouse)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N verify (what is YN ?)
Infobox references

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 drops.[5] Polyvinyl alcohol is used as an aid in suspension polymerizations. Its largest application in China is its use as a protective colloid to make polyvinyl acetate dispersions. In Japan its major use is the production of Vinylon fiber.[6] 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.[7]

Nowadays PVA-based polymers are being 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.[8]

Medically, it may also used as the embolic agent in a Uterine Fibroid Embolectomy (UFE) [9]

Polyvinyl acetals

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 U.S. and Western Europe.

Preparation

Unlike most vinyl polymers, PVA is not prepared by polymerization of the corresponding monomer as the monomer, vinyl alcohol, is thermodynamically unstable with respect to its tautomer 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.[6] Large producers include Kuraray (Japan, Europe, and US) and Sekisui Specialty Chemicals (US), 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 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 considerations

PVA is widely used, thus its toxicity and biodegradation are of interest. Solutions containing up to 5% PVA are nontoxic to fish.[3] It biodegrades slowly.[10]

See also

References
  1. "Poly(vinyl alcohol)_msds".
  2. Schnepf MJ, Mayer M, Kuttner C, Tebbe M, Wolf D, Dulle M, et al. (July 2017). "Nanorattles with tailored electric field enhancement". Nanoscale. 9 (27): 9376–9385. doi:10.1039/C7NR02952G. PMID 28656183.
  3. Hallensleben ML (2000). "Polyvinyl Compounds, Others". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a21_743.
  4. 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.
  5. 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.
  6. SRI Consulting CEH Report Polyvinyl Alcohol, published March 2007, abstract retrieved July 30, 2008.
  7. Lampman S (2003). Characterization and Failure Analysis of Plastics. ASM International. p. 29.
  8. Xu X, Zhao J, Wang M, Wang L, Yang J (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.
  9. Siskin GP (16 November 2018). Cho KJ (ed.). "Uterine Fibroid (Leiomyoma) Embolization and Imaging". WebMD LLC.
  10. 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.
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