Polyvinyl Alcohol - PVOH

Polyvinyl Alcohol - PVOH

Chapter 37 Polyvinyl Alcohol = PVOH Polyvinyl Alcohol: PVOH General Description: A white-to-cream granular powder, DuPont Elvanol polyvinyl alcohol (...

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Chapter 37

Polyvinyl Alcohol = PVOH Polyvinyl Alcohol: PVOH General Description: A white-to-cream granular powder, DuPont Elvanol polyvinyl alcohol (PVOH); is a water-soluble synthetic polymer with excellent film-forming, emulsifying, and adhesive properties. This versatile polymer offers a high oxygen barrier. [lo291 Elvanol71-30 is a medium-viscosity, hlly hydrolyzed grade ofpolyvinyl alcohol.[1030] Films cast from water solutions of Evanol polyvinyl alcohol and plasticizer are transparent, tough, and tear- and puncture-resistant.[1030] Film Processing Methods: Cast or blown films. Film Applications: PVOH films are used for hospital laundry bags that are added directly to the washing machine without the need for handling the contents. Other PVOH film applications include watersoluble packaging, release films, vacuum bagging, transfer printing, and water-soluble Biodegradable: PVOH film will totally biodegrade when composted and, when solubilized, will rapidly degrade and be assimilated by a number of acclimated microorganisms in waste-water streams. Use of water-soluble polyvinyl alcohol film for packaging preweighed quantities of materials such as dyes, detergents, bluing, powdered bleaches, and fungicides permits their addition to aqueous systems without breaking the package or removing the contents, thereby saving time and reducing material Physical Properties: The tensile strength of polyvinyl alcohol is similar to other packaging plastics, especially other water-soluble polymers. DuPont

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Elvanol7 1-30 forms tough, abrasion-resistant, tearresistant films. The strength, flexibility, and hardness of films vary with the plasticizer content and relative humidity.[1o3o] The tensile strength of Elvanol films increases substantially with stretching. After stretching five times its original length, film tensile strength increased from 69 MPa (10,000 psi) to more than 345 MPa (50,000 psi). [lo301 Elongation at break varies from less than 10% for dry, unplasticized films, to more than 400% for plasticized films of Elvanol 71-30 conditioned at 50% RH. A small amount of plasticizer substantially improves tear resistance, which is also higher in a warm, humid atmosphere than at low temperatures and humidity. The hardness and flexibility of plasticized Elvanol71-30 vary with the type and amount of plasticizer. Solubility: DuPont Elvanol71-30 is soluble in hot water, but has excellent resistance to cold water. Temperatures of 90" to 95°C are generally required for complete solution. Water is the only practical solvent for Elvanol, but substantial quantities of the lower alcohols can be added to water solutions without causing Only a few organic compounds have any appreciable solvent action on Elvanol 71-30. Most of these are polyhydroxy compounds (glycerin, ethylene glycol); amides (formamide, ethanol formamide, and ethanol acetamide); or amines, including ethanolamines and ethanolamine salts. Heat is required to dissolve even small amounts of Elvanol in solvents.[1030] Oil and Solvent Resistance: Elvanol71-30 is unaffected by animal and vegetable oils, greases, and petroleum hydrocarbons. L1 O3O]

Ch. 37: Polyvinyl Alcohol - PVOH

150 Optical Properties: In the infrared band, polyvinyl alcohol is practically opaque from 15 mm (15 microns) to 6.6 mm (6.6 microns) and again at 3 mm (3 microns).[l0301 Permeability: An outstanding property of polyvinyl alcohol is its high degree of impermeability to many gases. Continuous films or coatings of plasticized or unplasticized Elvanol provide excellent barriers against oxygen, nitrogen, carbon dioxide, hydrogen,

helium, and hydrogen-sulfide gases. Permeability to oxygen is extremely low compared with that of other polymers used as packaging films.[1030] Exceptions to the low permeability of polyvinyl alcohol to gases are ammonia and water vapor. [10301

Film Properties By Material Supplier Trade Name: See Tables 37-0 1 through 37-02.

Table 37-01. Physical Properties of Plasticized DuPont Elvanol71-30 Film

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Material Family Material Supplier Product Form

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POLYVINYL ALCOHOL (PVOH) DuPont Elvanol71-30 + 16% Glycerine Film

Reference Number

1030

Material Thickness (mm)

0.076

OPTICAL PROPERTIES

Wavelength: 0.25 pm (2,536 A) Transmitted (%)

77.5

Wavelength: 0.31 pm (3,130 A) Transmitted (%)

72.9

Wavelength: 0.37 pm (3,650 A) Transmitted (%)

81.1

PERMEABILITY PROPERTIES

I

TEST METHOD

Water Vapor Transmission Rate, 22°C (72°F) (g/m2/24hr) Relative Humidity in Film Faces,

ASTM E96-53T

0/50 (%)

7

50/72 (%)

147

Gas Permeability,3°C (cm3/m2) Relative Humidity, 02 (< 60%) (60-80%) (100%) Values shown are per mil offilm thickness. Permeabilitywas measured at 101 kPa (1 atm) for24 hours.

Ch. 37: Polyvinyl Alcohol - PVOH

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151 Table 37-02. Moisture Absorption of Unplasticized DuPont Elvanol Films

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Material Family Material Supplier Product Form

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DuPont Elvanol

Film

Reference Number

I

II

Relative Humidity (%) Moisture Absortion, Weight Gain

1030

I

35 1-2

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I

Films were dried at 100°C (212°F) before conditioning at humidity levels indicated.

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POLYVINYL ALCOHOL (PVOH)

55 3-5

I

I

I

80 7-10

I

100

I

25-30

I

Ch. 37: Polyvinyl Alcohol - PVOH