Review

admin (19677 pt) • 2024-Sep-30 07:43

PVOH, better known as Polyvinyl Alcohol (PVA) is a semi-crystalline chemical compound commercially produced from polyvinyl acetate hydrolysed by ester interchange in the presence of aqueous sodium hydroxide, anhydrous sodium methylate and methanol.

The name describes the structure of the molecule:

Polyvinyl is a polymer derived from vinyl monomers, compounds with the formula CH2=CH-R, where R is an atom or group of atoms.
Alcohol is a specific type of vinyl monomer in which the R group is a hydroxyl group (-OH), resulting in the formula CH₂CHOH.

The synthesis process takes place in different steps:

Polymerisation of vinyl acetate. The first step is the polymerisation of vinyl acetate monomers to form polyvinyl acetate (PVAc). Typically, free radical polymerisation is used, in which the vinyl acetate monomers are mixed with a free radical initiator, which can be a peroxide or an azo compound. The initiator starts the reaction by giving a free radical to the vinyl acetate, which then reacts with other vinyl acetate monomers to form a polymer chain.
Hydrolysis of polyvinyl acetate.PVAc is converted to PVA through a process called hydrolysis. The acetate groups of PVAc are replaced with hydroxyl groups. This process usually takes place by heating the PVAc in the presence of a catalyst such as sodium hydroxide or sulphuric acid and water. The degree of hydrolysis can be controlled to produce PVA with different properties: a higher degree of hydrolysis produces a more solvent-resistant PVA, while a lower degree of hydrolysis produces a more soluble PVA.

It appears in the form of a water-soluble white powder.

What it is used for and where

It is a synthetic polymer that, thanks to some interesting features, make it widely usable in medical, industrial, food applications: it is non-toxic, soluble in water, biocompatible and biodegradable in human tissues, insoluble in most organic solvents and has excellent gas barrier properties.

It is found in cleaning products, cosmetics, food packaging, agriculture, construction, water treatment, pharmaceuticals, soft contact lenses, wound dressing, etc.

Food

An ingredient listed in the European food additives list as E1203 with the function of preserving the integrity of ingredients that may degrade with moisture, oxygen or other environmental components. It has the function of masking odours and flavours.

Cosmetics

Film-forming agent. It produces a continuous ultra-thin film with an optimal balance of cohesion, adhesion and stickiness on the skin or hair to counteract or limit damage from external phenomena such as chemicals, UV rays and pollution.

Viscosity control agent. It controls and adapts viscosity to the required level for optimal chemical and physical stability of the product and dosage in gels, suspensions, emulsions, solutions.

Medical

In this study, fish collagen and polyvinyl alcohol (Col/PVA) dual-layer membrane were developed via a combined freezing/thawing and layer coating method (1).

A blue polyvinyl alcohol-iodine (PAI) complex-based antibacterial hydrogel is explored as a new generation of biocompatible iodine-based bactericides (2).

In this study a new approach for treating open wounds that is based on sticky and dissolvable polyvinyl alcohol (3).

Pharmaceuticals

Polyvinyl alcohol has a viscous consistency and due to this characteristic is used in film coatings of capsules, tablets and others.

Other uses

The findings of this work disclosed a new perspective regarding material considerations for the preparation of polyvinyl alcohol -based solid dosage forms by coupling hot melt extrusion (HME) and FDM-3DP (4).

Safety

Orally administered polyvinyl alcohol is relatively harmless (5).

The most relevant studies on this ingredient have been selected with a summary of their contents:

Polyvinyl Alcohol studies

Molecular Formula: C₂H₄O [-CH₂CHOH-]_n
Molecular Weight: 44.05 g/mol
CAS: 9002-89-5
UNII 532B59J990
EC Number: 209-183-3 618-340-9
DSSTox Substance ID: DTXSID4031930 DTXSID8051467
MDL number MFCD00081922

Synonyms:

Mowiol® 18-88
Ethenol
Vinyl alcohol
Hydroxyethene
Hydroxyethylene
Polyvinyl Alcohol
Ethenol, homopolymer
Elvanol
Gohsenol
Poval
Polyviol
PVA
Rhodoviol
Alkotex
Polydesis
Gelvatol
Polyvinol
Covol
Vinalak
Lemol
Vinarol
Gohsenol
Vinarole
Lamephil
Alvyl

References_______________________________________________________________

(1) Zhou T, Chen S, Ding X, Hu Z, Cen L, Zhang X. Fabrication and Characterization of Collagen/PVA Dual-Layer Membranes for Periodontal Bone Regeneration. Front Bioeng Biotechnol. 2021 Jun 9;9:630977. doi: 10.3389/fbioe.2021.630977.

(2) Miao Z, Sun Y, Tao Z, Chen Y, Ma Y, Zhu D, Huang X, Zha Z. Thermochromic Polyvinyl Alcohol-Iodine Hydrogels with Safe Threshold Temperature for Infectious Wound Healing. Adv Healthc Mater. 2021 Jun 24:e2100722. doi: 10.1002/adhm.202100722.

(3) Ben David N, Mafi M, Nyska A, Gross A, Greiner A, Mizrahi B. Bacillus subtilis in PVA Microparticles for Treating Open Wounds. ACS Omega. 2021 May 20;6(21):13647-13653. doi: 10.1021/acsomega.1c00790.

(4) Crișan AG, Porfire A, Ambrus R, Katona G, Rus LM, Porav AS, Ilyés K, Tomuță I. Polyvinyl Alcohol-Based 3D Printed Tablets: Novel Insight into the Influence of Polymer Particle Size on Filament Preparation and Drug Release Performance. Pharmaceuticals (Basel). 2021 May 1;14(5):418. doi: 10.3390/ph14050418.

Abstract. Three-dimensional printing (3DP) by fused deposition modeling (FDM) has gained momentum as a promising pharmaceutical manufacturing method due to encouraging forward-looking perspectives in personalized medicine preparation. The current challenges the technology has for applicability in the fabrication of solid dosage forms include the limited range of suitable pharmaceutical grade thermoplastic materials. Hence, it is important to investigate the implications of variable properties of the polymeric carrier on the preparation steps and the final output, as versatile products could be obtained by using the same material. In this study, we highlighted the influence of polyvinyl alcohol (PVA) particle size on the residence time of the mixtures in the extruder during the drug-loaded filament preparation step and the consequent impact on drug release from the 3D printed dosage form. We enhanced filament printability by exploiting the plasticizing potential of the active pharmaceutical ingredient (API) and we explored a channeled tablet model as a design strategy for dissolution facilitating purposes. Our findings disclosed a new perspective regarding material considerations for the preparation of PVA-based solid dosage forms by coupling hot melt extrusion (HME) and FDM-3DP.

(5) DeMerlis CC, Schoneker DR. Review of the oral toxicity of polyvinyl alcohol (PVA). Food Chem Toxicol. 2003 Mar;41(3):319-26. doi: 10.1016/s0278-6915(02)00258-2.

Abstract. Polyvinyl alcohols (PVA) (CAS no. 9002-89-5) are synthetic polymers used in a wide range of industrial, commercial, medical and food applications. The purpose of this review, this critical evaluation of the available information on PVA, is to support the safety of PVA as a coating agent for pharmaceutical and dietary supplement products. All the available information on PVA gleaned from a comprehensive search of the scientific literature were critically evaluated. Orally administered PVA is relatively harmless. The safety of PVA is based on the following: (1) the acute oral toxicity of PVA is very low, with LD(50)s in the range of 15-20 g/kg; (2) orally administered PVA is very poorly absorbed from the gastrointestinal tract; (3) PVA does not accumulate in the body when administered orally; (4) PVA is not mutagenic or clastogenic; and (5) NOAELs of orally administered PVA in male and female rats were 5000 mg/kg body weight/day in the 90-day dietary study and 5000 mg/kg body weight/day in the two-generation reproduction study, which was the highest dose tested. A critical evaluation of the existing information on PVA supports its safety for use as a coating agent for pharmaceutical and dietary supplement products.

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