Properties of Polyvinyl Alcohol (PVA)
How to make PVA
Testing some of the properties
Procedure:
1. Place 100ml of Water into a 250 ml Beaker and heat to
boiling.
2. Measure 4.0 grams of PVA solid into a 100 ml Beaker and add
20 ml of ethandiol.
3. Slowly pour the PVA solution into the boiling water with
constant stirring. Be sure to add the PVA slowly to guarantee a
homogeneous solution.
4. Note the properties of the solution as the PVA solution mixes
with the water.
5. Once the PVA has mixed with the water, remove the beaker
from the heating source using a Hot Hand or Glove.
6. Place 5 mls of the PVA solution in a small aluminum pan and
evaporate the water from the PVA by heating. Remove the pan
from the heating source when the water has evaporated. Note
the properties of the residue.
7. Place 10 ml of the PVA solution into a graduated cylinder.
8. Slowly add Propanone (Acetone) to the PVA in the graduated
cylinder.
9. Remove any solid produced at the interface of the two liquids.
Dry the product with a paper towel.
10. Place 20 mls of the PVA solution into a small dish.
11. Slowly add to the dish with stirring the saturated borate ion
solution provided.
12. Note the properties of this mixture. Remove any gel or solid
produced and record any properties of this material.
Questions
1. What molecular feature (Functional Group) on the PVA molecule
allows the PVA to be miscible in the water?
2. How does temperature affect the solubility of the solid PVA?
3. Does propanone mix with water? Is Propanone a very polar
molecule?
4. Is PVA soluble in Propanone?
5. When you added the Propanone to the PVA solution what was the
solid produced at the interface?
6. What are some of the properties of the solid produced?
7. When you dried the PVA solution what were the properties of the
residue?
8. When you added the Borate Ions to the PVA solution what did the
ions due to the solution?
9. Borate ions have a central atom surrounded by four OH- ions.
What do you think the borate ions are doing the molecules in the
solution?
10. The gel or solid produced has distinct properties. Is the material
produced a pure crystalline solid or an amorphous solid?
Description
Polyvinyl Alcohol is a white and granular, it is soluble in hot water but insoluble in
cold water and common organic solvents. For many applications Polyvinyl Alcohol is
prepared in water solutions. On evaporation of water, transparent films are formed
which have high tensile strength and tear resistance. The binder characteristics of
Polyvinyl Alcohol offer excellent adhesion to porous, water-absorbent surfaces.
Typical Properties
Physical Properties Polyvinyl Alcohol
Form
granular
Color
white
Hydrolysis, mole %
a
99.0-99.8
b
Saponification number
3-12
Residual polyvinyl acetate, weight %
0.5-1.8
Viscosity, mPa·s (cP)c
27-33
Solution pH
5.0-7.0
Volatiles, % max
5
a
Ash (as Na2O), % max
3
1.0
3
Bulk density, kg/m (lb/ft )
Specific gravity
400-432 (25-27)
1.30
3
Resin density, kg/m (lb/gal)
Specific volume, m3/kg(in3/lb)
1294 (10.8)
7.7 x 10-4 (21.3)
Refractive index
1.54
Hardness, Shore unplasticized
>100
Specific heat, J/kg·K(cal/g/°C)
1674 (0.4)
a
b
c
dry basis.
milligrams potassium hydroxide per gram polymer.
viscosity of a 4% aqueous solution at 20°C (68°F), determined by Hoeppler falling ball
method.
Suggested End-Uses
Polyvinyl Alcohol offers a combination of excellent film forming and
binder characteristics, along with insolubility in cold water and organic
solvents. This combination of characteristics is useful in a variety of
applications.
Adhesives
In adhesive applications Polyvinyl Alcohol can be used alone or often in
combination with extenders such as starch, dextrin or clay. As the
proportion of Polyvinyl Alcohol increases, the adhesive strength and water
resistance also improve. Examples of Polyvinyl Alcohol adhesives
applications include:
•
•
•
•
•
for paper and paperboard, alone or in combination with other additives;
as a component in industrial adhesives for bonding paper, textiles, leather, films
and porous substrates;
for laminating adhesives which are used in the manufacture of solid fiberboard,
linerboard, spiral wound tubes and cores, and laminated specialties;
in bag adhesives and pastes; and
as an adhesive in corrugated container board.
Paper and Paperboard Sizing and Coatings
In sizing and coatings for paper and paperboard Polyvinyl Alcohol can be
used alone or combined with extenders or modifiers. The proportion of
Polyvinyl Alcohol to be used depends on desired physical properties and
economics. Some specific paper uses include:
•
•
•
for fine writing and printing papers as surface size material with starch;
as grease-proof coating or release coating on paper specialties; and
as binder in pigmented coatings to provide greater opacity: due to improved
optical properties, part of the TiO2 may be substituted by a lower cost pigment
such as clay.
Textiles
In addition to providing strength properties, Polyvinyl Alcohol® 71-30 is
flexible and resists abrasion when used in textile applications such as:
•
warp size for spun yarns:
•
•
inish for textiles in combination with thermosetting resins; and
effective binder for some nonwoven structures.
Films
Unsupported films cast from water solutions of Polyvinyl Alcohol and
plasticizer are transparent, tough, tear-resistant and puncture-resistant.
Polyvinyl Alcohol provides a unique combination of properties whereby
films have water solubility, in addition to resistance to oils, grease and
solvents, and impermeability to most gases. These properties make films
of Polyvinyl Alcohol suitable for dissolvable unit packages and hospital
laundry bags.
Building Products
Because Polyvinyl Alcohol is an effective binder for solid particles such as
pigments, ceramics, cements and plastics, it finds utility in building
products. It is used as a binder in ceiling tile, floor coatings and particle
board.
Other Uses
The general properties of Polyvinyl Alcohol make it useful in other
applications including:
•
•
•
hoses, gaskets, pipe and gloves where its oil and solvent barrier properties are
important;
as an emulsifying agent in emulsions and latices; and
as an additive for strength to concrete and cements.
Properties in Solution
Polyvinyl Alcohol often is prepared in a water solution. The viscosity of water
solutions of Polyvinyl Alcohol varies with concentration (solids) and
temperature. The relationships between viscosity, concentration and
temperature are shown in Figures 1 and 2. Elvanol is the Dupont product
name for PVA.