Coatings Technology Handbook Episode 2 Part 5 pptx

53

-4

Coatings Technology Handbook, Third Edition

gloss.

12

Parasubstituted phenolic novolak resins that have been modified with rosin make excellent ink
additives. Rosin modification of the phenolic resin raises the melting point and gives the phenolic excellent
oil solubility. The formulations consist of a phenolic resin, oils, pigments or dyes, driers, and lubricants
or plasticizers.

13

The proper balance of ingredients gives the desired combination of hardness, viscosity,
penetration, and drying rate.

53.4 Epoxy Hardeners

Phenolic resins may be combined with epoxy resins for use in protective coatings. Phenolic–epoxy
products are also used in laminates, prepreg manufacturing, molding materials, and electrical insulation
coatings. The phenolic resin is used as a coreactant to produce thermoset systems with improved heat
and chemical resistance. Non-heat-reactive (novolak) resins are used to cross-link the epoxies. The epoxy
resins are typically epoxy–phenolics or bisphenol A-based resins.

14

The reaction mechanism is different
from the resole–epoxy reactions. The coating is heat-activated and uses a base catalyst such as an amine,
dicyandiamide, or an imidazole.

15

The phenolic hydroxyl group reacts with the epoxy group to form a
polyether structure, which has an advantage, because no volatiles are released during cure. This allows
for thick films to be produced with low shrinkage and no voids from volatile emission. The phe-
nolic–epoxy reaction using a base catalyst can be demonstrated as follows:
For critical electrical applications, “high purity” resins are used. These products are made according
to stringent specifications limiting the amount of water, ions, and free monomers present in the resin.

53.5 Summary

Phenolic resins were one of the first synthetic polymers to have widespread commercial importance.
Their outstanding performance properties have given them a permanent role in the coatings industry.
They are used in applications ranging from railroad tank cars to carbonless copy paper. Phenolic resins
are also used on a wide variety of substrates including metal, wood, paper, and ceramics. There are so
many types of phenolic resin available to the marketplace that a particular resin can be selected for
virtually any application.
Phenolic resins should not be overlooked when choosing a high performance polymer. Phenolics
currently do not receive the same attention as some of the more recently developed polymers, but for
many applications, there is simply no substitute for phenolic resins. Phenolics will continue to have an
important role in the coating industry because of their versatility, coatings properties, and reasonable price.
OH
OH
CH
2

CH
2
CH
2
CH
2
CH
2
CH
2
H
2
C
CH
.
CH
2
O-R
OCH
2
-CH CH
2
n
n
n
+
O
O
Base
∆

OCH
2
CH(OH)CH
2
O-R
OCH
2
-CH(OH)CH
2
O
OCH
2
CH(OH)CH
2
O-R
OCH
2
-CH(OH)CH
2
O

DK4036_book.fm Page 4 Monday, April 25, 2005 12:18 PM
© 2006 by Taylor & Francis Group, LLC

Phenolic Resins

53

-5

References

1. J. S. Fry, C. N. Merriam, and W. H. Boyd,

Chemistry and Technology of Phenolic Resins and Coatings

,
in ACS Symposium Series.

Applied Polymer Science.

Washington, DC: American Chemical Society,
1985, p. 1147.
2. R. T. Morrison, and R. N. Boyd,

Organic Chemistry

, 3rd ed. Boston: Allyn and Bacon, 1973, p. 1147.
3. J. S. Fry, C. S. Merriam, and W. H. Boyd,

Chemistry and Technology of Phenolic Resins and Coatings

,
ACS Symposium Series,

Applied Polymer Science.

Washington, DC: American Chemical Society,
1985, p. 1149.
4. Union Carbide Corp.,

Formulation Suggestions

—

Durable Phenolic Baking Coatings for Rigid Metal
Substrates

(F-60675), 1988.
5. A Knop, and L. Pilato,

Phenolic Resins.

Berlin: Springer-Verlag, 1985, p. 247.
6. Union Carbide Corp.,

Ucar Phenolic Resin BKS-7570

(F-60689), 1988.
7. R. W. Martin,

The Chemistry of Phenolic Resins.

New York: Wiley, 1956, p. 203.
8. R. R Myers and J. S. Long,

Film Forming Compositions.

New York: Dekker, 1972, p. 155.
9. R. W. Martin,

The Chemistry of Phenolic Resins.

New York: Wiley, 1956, p. 205.
10. R. G. Middlemiss,

J. Water Borne Coat.

, November (1985).
11. S. H. Richardson,

Paint Varnish Prod.,

August (1955).
12. A. Knop, and W. Scheib,

Chemistry and Application of Phenolic Resins.

Berlin: Springer-Verlag,
1979, p. 192.
13. National Association of Printing Ink Manufacturers,

Pattern Printing Ink Formulae.

NAPIM, 1974.
14. J. S. Fry,

Ucar Phenolic Resins for Epoxy Hardeners.

Union Carbide Corp. (P-)-3(57).

15. U. S. Patent 3,493,630, Union Carbide Corp.

DK4036_book.fm Page 5 Monday, April 25, 2005 12:18 PM
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54

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54

Coal Tar and

Asphalt Coatings

54.1 Coal Tar Types

54-

1
54.2 Asphaltic Types

54-

3
Bibliography

54-

4

Coal tar coatings have been used for many centuries because of their resistance to water and biological
organisms. Coatings based on asphalt have been developed for over a century. This is a brief review of
the materials.

54.1 Coal Tar Types

Bituminous coal, a very complex chemical mixture, decomposes into simpler components when heated
in retorts without air above 700

°

C (1292

°

F). Gas, aqueous vapor, and coal tar are driven off, leaving coke
as residue. The coat tar is dehydrated and heated in stills to yield oil and coal tar pitch. Depending on
the source of the coal tar and the amount of heat applied, pitches of different characteristics are obtained.
When used as bases for superior coatings, coal tar pitches are reprocessed, and any corrosion-accelerating
substances are removed. Various types of coal tar pitches are then blended together.
The outstanding quality of coal tar paints is their extremely low permeability, their high electrolytic
resistance, and their remarkable resistance to the disintegrating action of water. There are hardly any
materials, old or new, that are as water resistant as properly compounded coal tar coatings. They will
not be affected by mineral oil but may be dissolved by vegetable and animal oil, grease, and detergents,
if they are in direct contact with them. Their resistance to weak mineral acids, alkalis, salts, brine solutions,
and other aggressive chemicals is good. Furthermore, coal tar paints give more value per dollar than any
other protective coating. This fact should not be overlooked when selecting paint for a certain job.
Coal tar paints are made by dissolving the processed pitch or blend of pitches in suitable solvents. Skill
and experience are essential in compounding coal tar paints because similar physical characteristics of
raw materials do not necessarily mean similar behavior of the finished product under exposure. The raw

materials selected for the blending, the degree of refining, and the addition of other modifiers, often in
small quantities, decide the final merit of the coating.
There are five main types of coal tar coatings:
1. Thin coal tar pitch solutions without any filler
2. Heavy coal tar pitch solutions with inert fillers added
3. Very heavy coal tar pitch coatings containing inert fillers possessing a thixotropic gel structure but
only medium inherent viscosity
4. Heavy coal tar emulsions containing inert fillers and having low inherent viscosity
5. Hot applied coal tar coatings

Henry R. Stoner

Henry R. Stoner Associates

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54

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Coatings Technology Handbook, Third Edition

The first three types are solutions and have about the same chemical and water resistance. They vary
mainly in the thickness of the film that can be laid down in a single coat. The fourth type, coal tar
emulsions, consists of dispersions of coal tar pitch in water and are inferior in corrosion resistance to
the solution type. This is not a fault of the pitch itself but is caused by the higher permeability of the
applied film. Pitch particles dispersed in water are relatively large and do not coalesce as completely after
drying as the much smaller dissolved pitch particles do. But coal tar emulsions have other very good
features that will be mentioned later.

The fifth type, coal tar pitch reinforced with inert filler and applied in a molten state over a primer, is
called in the trade, coal tar enamel. These enamels have all the good qualities of coal tar paints, but in a
higher degree, because the coating is very thick and does not depend on the evaporation of solvent to set.
Type 1 is a thin coal tar solution of low viscosity with a solids content of 60 to 70% and a spreading
rate of 300 to 400 square feet per gallon, and it gives an approximate thickness of 1 to 2 mils per coat.
This thickness cannot be increased because the thin solution cannot be applied at a lower rate without
sagging. Type 2 is designed to achieve a heavier coat; a filler coal tar solution must be used, which, in
addition to its higher solids content, can be applied at approximately 180 square feet per gallon without
sagging. This produces an approximate dry film thickness of 6 mils. To apply even heavier coatings by
brush, a gel must be selected that can be applied at the low rate of 75 square feet per gallon without
sagging. This will produce a dry film thickness of approximately 16 mils in one coat. Coal tar emulsions
will not sag at a coverage of 75 square feet per gallon and will give approximately a 12 mil dry film
thickness in one coat.
Coal tar paints afford protection by the mechanical exclusion of moisture and air. If they are applied
as a continuous film without holidays, they give almost perfect protection. As it is impossible to avoid
pinholes and flaws in a one-coat application, more than one coat will be necessary. They dry by solvent
evaporation only.
Concrete, as a rule, can be protected with thin coal tar solutions, but steel requires heavier coatings
that will form an almost impervious barrier against severe corrosive influences.
All coal tar paints “alligator,” more or less, in the sun. The paint will look like an alligator skin, and
hence, the name alligatoring. This alligatoring is a surface defect. It is brought about by the hardening
of the upper layer of the film, stimulated by the sun’s rays. This causes the upper layer to contract, crack,
and slip over the lower stratum which is still soft. If not enough coats are applied, these alligator marks
can go right down to metal, opening the path for atmospheric corrosion. Alligatoring does not (or only
to a limited degree) occur under water, where the coating is protected from the rays of the sun. Coal tar
emulsions do not produce this phenomenon, probably because the pitch particles are not fused as tightly
as in solution types; therefore, coal tar emulsions can be used as topcoats over badly alligatoring heavy
coal tar paints. Bear in mind that these emulsions have less protection capabilities in immersion service
and are not recommended for such use.
There are several popular methods to prevent alligatoring of heavy coal tar coatings, which are

temporarily exposed to sun and air before submersion. The older method uses a whitewash. Add slowly
and simultaneously 150 lb of processed quicklime and 1 gal of boiled linseed oil to 50 gal of water,
containing 10 lb of salt dissolved therein. While being mixed and for 15 min thereafter, the mixture shall
be stirred continuously and allowed to cool. It shall be free from lumps and foreign matter. The whitewash
shall be aged for at least 3 days before application (NAVDOCKS Specification 34 Yc).
A more current approach is to use an acrylic latex paint, or a similar emulsion paint applied to the
surface of the coal tar coating. However, note that discoloration of this paint’s film by the oils in the coal
tar coating is not deemed as a cause for failure.
The solvents used in coal tar pitches are strong in odor, and adequate ventilation is necessary during
applications and drying. Coal tar emulsions, which use water as a volatile thinner, are in this respect
superior and should be used where proper ventilation is not possible.
Coal tar paints give excellent protection at low cost in dam and flood control installations, penstocks,
piers, marine work, etc.

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55

-1

55

Vulcanizate
Thermoplastic

Elastomers

55.1 Introduction

55-

1
55.2 Properties

55-

1
55.3 Processing

55-

2
55.4 Uses of TPV

55-

2

55.1 Introduction

A thermoplastic elastomer (TPE) is a material that is processed in the same manner as a conventional
thermoplastic but gives a finished article with properties and performance similar to those of a thermoset
rubber. Thermoplastic vulcanizates (TPVs, referred to as elastomeric alloys in some earlier literature) are
a generic class of TPEs with a chemically cross-linked rubber phase in a continuous matrix of thermo-
plastic. TPVs thus have properties significantly better than those of the same rubber/thermoplastic
composition with little or no cross-linking of the rubber phase (i.e., and olefinic blend).
performance, moderate cost TPEs. They have performance and cost higher than those of the styrenic
and olefinic blend TPEs and lower than those of the polyurethanes, copolyesters, and polyamides.

55.2 Properties

The cross-linking of a TPV rubber phase gives improvement to a number of properties of a specific
rubber/thermoplastic composition, such as EPDM rubber/polypropylene (PP). These property improve-
ments include tensile strength, tensile and compression set resistance, stress relaxation, fluid resistance,
and retention of properties at elevated temperature. These improvements qualify TPVs for many uses
where a simple rubber/polyolefin blend would be inadequate.
Key parameters for the premium performance of a TPV are (1) the degree of cross-linking of the rubber
phase, (2) the degree of dispersion of the rubber phase in the thermoplastic phase, and (3) the thermody-
namic compatibility of the polymers present. TPV performance is known to be improved by greater cross-
linking, dispersion, and polymer compatibility. TPVs with high polymer compatibility have no need for a
compatibilizer; those with low compatibility (e.g., NBR rubber/PP) will need one to stabilize the intermin-
gling of the rubber and thermoplastic chains. The mutual compatibility of the rubber and thermoplastic
polymers will increase as the difference in their solubility parameters (i.e., cohesive energy density) decreases.
The hardness of TPVs ranges from 35 Shore A up to 50 Shore D. EPDM/PP TPVs are generally suitable
for use in air from –60

°

C to 135

°

C, and those from nitrile rubber/PP have a range in air from –40

°

C to

Charles P. Rader

Advanced Elastomer Systems, L.P.

DK4036_book.fm Page 1 Monday, April 25, 2005 12:18 PM
© 2006 by Taylor & Francis Group, LLC
Figure 55.1 compares the generic classes of TPEs by performance and cost. The TPVs are medium

Vulcanizate Thermoplastic Elastomers

55

-3

of 100,000 MT should have been reached between 2000 and 2003

.

Why has this growth been so great?
Perhaps the principal reasons are (1) TPVs are the closest approach of any TPE to the properties and
performance of a conventional thermoset rubber, and (2) TPVs permit close-to-optimum exploitation
of the economic advantages inherent in the processing of a TPE.
To day’s applications of TPVs number well into the thousands, penetrating virtually all major uses of
rubber — but with one massive exception, that of penumatic tires, which consume slightly more than
one-half of the rubber produced in the world. In other rubber application areas, TPVs have been
eminently successful. A leader in this success has been the automotive segment, where these materials
enjoy uses in convoluted protective boots, seals, jacketing, hose, grommets, weather stripping, and
numerous other specific parts. TPVs function well in under-the-hood uses where other TPEs are inad-
equate for the service temperature, which continues to progress upward.
Architectural uses also provide a ready market for TPEs. Hundreds of large buildings around the world
now employ window glazing and/or chemical expansion joints extruded from an EPDM/PP TPV.

Mechanical rubber goods embrace those uses in which a molded or extruded rubber article is a component
part of a useful assembly. Major TPV uses in this area include household appliances, office equipment,
toys, and other items requiring the use of boots, bushings, seals, tubing, and other rubber articles.
EPDM/PP TPVs have excellent electrical insulating properties — dielectric constant, resistivity, dielec-
tric strength, power factor — that render them quite suitable for use as primary insulators or as jacketing
materials. Electrically conducting wire can readily be coated by crosshead extrusion of a TPV for use in
automotive, construction, industrial, appliance, and many other applications.
EPDM/PP TPVs have unusually low toxicity for a rubber. This explains their broad utility for direct
contact with foods and potable water. TPVs have also found use in health care applications in hospitals
and physician’s offices and in pharmaceutical applications involving direct contact with preparations to
be taken orally or injected into the bloodstream.

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56

-1

56

Olefinic Thermoplastic

Elastomers

56.1 Introduction

56-

1

56.2 Properties

56-

2

Limitations of TPOE Compounds

56.3 Usage

56-

2

56.1 Introduction

Olefinic elastomers based upon ethylene-propylene and/or ethylene-propylene-diene monomer rubbers
(EPR or EPDM) are thermoplastic by virtue of their alloying with isostatic crystalline polypropylene
and/or high-density polyethylene (HDPE). These products are produced by high intensity mixing in
Banburies continuous mixers, and extruders.
The olefin plastics are either pellets or reactor beads, while the rubber can be in bale form for mixing
in a Banbury. For mixing in an extruder or continuous mixer, the rubber must be converted to a pellet
or granular particle. The high intensity mixing results in a simultaneous comminution of the polymers,
with the olefin as the continuous phase and the rubber the dispersed phase. Thus the blend is thermo-
plastic: the blend viscosity is largely controlled by the choice of polyolefin, and the elasticity is controlled
by the rubber segment of the blend.
Thermoplastic olefinic elastomers (TPOEs) can be manufactured by blending alone, which limits the
elevated temperature properties of the mix, or by blending and cross-linking

in situ

during the com-
pounding operation. When the compounds are cross-linked, the elevated temperature properties are
enhanced. The processing “nerve” of the blend is reduced, and thinner, more complex extruded products
are possible.
The polymer compound is made broadly versatile by the inclusion of a great variety of additives. In
addition to the initial choice of polymers, the ratio of plastic to rubber (hard to soft segment) controls
the hardness of the compound to some degree. The use of high permanence petroleum oils that function
as permanent plasticizers assists in the control of hardness. Flexural modulus or toughness is more readily
controlled by the rubber polymer. The combined use of these ingredients results in a wide variety of
physical properties.
Fillers, such as fine particle calcium carbonates, clays, talc, and silicas are all usable. TPOE compounds
cannot be made to be clear; but very pale, pastel colors are possible. Translucent colors are possible in
thin sections. For outdoor use, protection against ultraviolet radiation is needed. The general-purpose
compounds are not flame retardant inherently and require a package of halogen donor additives to pass
any necessary specifications.

Jesse Edenbaum

Consultant

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© 2006 by Taylor & Francis Group, LLC
Coating Applications • Primer Systems

57

-1

57

Ethylene Vinyl
Alcohol Copolymer

(EVOH) Resins

57.1 Polymer

57-

1
57.2 Barrier Properties

57-

1
57.3 Regulatory Approval

57-

4
57.4 Fabrication Methods

57-

4

57.1 Polymer

Ethylene vinyl alcohol (EVOH) resins are hydrolyzed copolymers of vinyl acetate and ethylene. The vinyl

alcohol base has exceptionally high gas barrier properties, but it is water soluble and difficult to process.
By copolymerizing ethylene with vinyl alcohol, the high gas barrier properties are retained and significant
improvements are achieved in moisture resistance and processibility.
A typical reaction for producing EVOH resins is shown on page 57-3

.

Under proper conditions, this
reaction yields a copolymer that is more than 99% hydrolyzed.

57.2 Barrier Properties

EVOH copolymers are highly crystalline, and their properties are highly dependent on the relative
concentration of the comonomers. Generally speaking, as the ethylene content increases, the gas barrier
properties decreases, the moisture barrier properties improve, and the resins are processed more easily
The presence of a hydroxyl group in the molecular chain renders the gas barrier properties of the
properties decrease. However, by proper use of companion materials in a multilayer structure, this effect
can be minimized.
content of the EVOH and maintain superior gas barrier properties. In this article, any aqueous-based
food is considered to be 100% relative humidity; the storage environment is shown at relative humidities
of 65 and 85%.

R. H. Foster

Eval Company of America

DK4036_book.fm Page 1 Monday, April 25, 2005 12:18 PM
© 2006 by Taylor & Francis Group, LLC
Ta ble 57.1 lists the range of EVOH resins presently available.
(see Table 57.2).

EVOH resins sensitive to moisture. As the moisture content of the resin increases, the gas barrier
Ta ble 57.3 shows how the combination of different materials can be used to minimize the moisture

Ethylene Vinyl Alcohol Copolymer (EVOH) Resins

57

-3

In addition to being outstanding as barrier properties, EVOH resins offer excellent barriers to a variety
of flavors, aromas, and solvents (see Table 57.4 and Table 57.5).

TA BLE 57.4

Flavor Barrier Data (Citrus and Tropical Flavors)

a

Film

b

Thickness
(

µ

m)

Duration

1 h 2 h 15 h 1 Day 4 Days 35 Days

EVOH-32 15 A A A A A A
EVOH-44 15 A A A A A A
BO EVHO 15 A A A A A A
BO Nylon 15AABBB B
OPP 20 B B C C C C
PVDC 25 A A B B B B
LDPE 50 D D D D D D

a

Key: A, no detection; B, faint flavor; C, partial flavor; D, flavor clearly distinguished.

b

BO EVOH, biaxially oriented EVOH; BO Nylon, biaxially oriented nylon; OPP, ori-
ented polypropylene; PVDC, polyvinylidene chloride; LDPE, low density polyethylene.

TA BLE 57.5

Flavor, Aroma, and Solvent Barrier Properties

a

Resin

b

Allyl Sulfide:

Garlic-Food Type
(Croutons, Snacks,
Salad Dressins)
Acetic Acid
Vinegar-Food
Type (Cheddar
Cheese, Snacks,
Condiments)
Ethylene
Acetate:
Laminating
Adhesive
Solvent Residual
To l u ene:
Printing Ink
Solvent
Residual
Methyl
Ethyl Ketone
Printing Ink
Solvent Residual

HDPE-Nylon-EVa 0.00008 0.92 0.03 0.02 0.005
HDPE-EVOH-EVA 0.00075 0.035 0.0043 0.007 0.035
PVDC-PP-PVDC 0.0068 1.98 0.34 0.22 3.09
OPP-HDPE-EVOH-EVA 0.00076 1.40 0.15 0.00003 0.09
EVA-Glassine-PVDC 0.50 4.18 6.47 3.15 15.1

a

g/24 h, m

2

, 100 pm at 70

°

F.

b

HDPE, high-density polyethylene; EVA, ethylene vinyl acetate; PVDC, polyvinylidene chloride; OPP, oriented polypro-
pylene.
+
+
CxC
—
—
—
—
HH
HH
CyC
—
—
—
—
HH
HO

—(CH
2
—CH
2
)
x
—(CH
2
—CH)
y
—
——
O
O
C
—
CH
3
Ethylene Vinyl Acetate CopolymerVinyl Acetate
Monomer
Ethylene
Monomer
(CH
2
—CH
2
)
x
—(CH
2

—CH)
y
(CH
2
—CH
2
)
x
—(CH
2
—CH)
y
——
O
C
C
—
CH
3
Ethylene Vinyl Acetate Copolymer Ethylene Vinyl Alcohol Copolymer
(EVOH)
Heat
Catalyst

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Ethylene Vinyl Alcohol Copolymer (EVOH) Resins

57

-5

•Using EVOH films that are laminated to other substrates or coated with other materials
•Coating various substrates or monolayer containers with EVOH resins
Generally speaking, coextrusion or lamination is used for structures in which the EVOH layer must
be protected from the effects of moisture. When packaging aqueous-based products (tomato ketchup,
barbeque sauce, etc.), various combinations of less costly polyolefins are used to provide structural strength
and to prevent excess moisture from reaching the EVOH barrier layer and lowering gas barrier properties.
Coating techniques can also be used to produce multilayered structures by the use of either multiple
coatings or coextrusion coating. The resulting structure will be very similar to a coextruded structure.
Spray, dip, and/or roller coating of EVOH resins are used to produce containers for carbonated
beverages or to establish a barrier to solvents, aromas, or odor. Manufacturers of such products include
Kuraray Company Ltd. (Eval resins) and Nippon Gohsei (Soarnol resins) in Japan and Solvay (Clarene
resins) in Europe.

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58

-1

58

Elastomeric Alloy
Thermoplastic

Elastomers

58.1 Properties

58-

1
58.2 Processing

58-

2
58.3 Uses of Elastomeric Alloys

58-

2
A thermoplastic elastomer (TPE) is a material with the functional performance of a thermoset rubber
but the processibility of a conventional thermoplastic. Elastomeric alloys (EAs) are a generic class of TPEs
composed of two or more polymer systems between which a synergistic interaction has arisen, giving
rise to properties significantly better than those expected from a single blend of these polymer systems.
EAs are medium performance, moderate cost TPEs.
performance and cost than either the styrenic or olefinic blend TPEs, whereas thermoplastic polyure-
thanes, copolyesters, and polyamides cost more and give higher performance than EAs.

58.1 Properties

Elastomeric alloys may have either two phases or a single phase. A two-phase EA is an alloy of vulcanized
rubber with a thermoplastic polyolefin. The alloying of these two polymeric phases gives rise to higher
ultimate tensile strength, improved retention of physical properties at elevated temperature, improved
resistance to hydrocarbon fluids, lower compression set, and lower tension set. These properties thus
qualify EAs for applications for which a simple rubber-polyolefin blend would be inadequate.

The need for a compatibilizer to stabilize intermingling of the rubber and polyolefin phases of a two-
phase EA will be determined by their relative solubility parameters. Having essentially equal solubility
parameters for the two phases eliminates the need for a compatibilizer, whereas a significant difference
between the solubility parameters requires a compatibilizer.
Single-phase EAs are said to consist of an ethylene vinyl acetate-acrylate ester-polyolefin blend with
significant plasticizer content. They may or may not contain carbon black.
Two-phase EAs range in hardness from 55 Shore A to 50 Shore D. EAs derived from ethylene propylene
diene monomer (EPDM) rubber and polypropylene have a service temperature range from –60

°

C to
135

°

C in air. Two-phase EAs from nitrile rubber and polypropylene have a service temperature ranging
from 40

°

C to 125

°

C in air. The specific gravity of single-phase EAs ranges from 1.2 to 1.3, and that of
two-phase EAs from 0.9 to 1.0. Although the properties of an EA are quite competitive with those of a
thermoset rubber, the ultimate tensile strength is generally significantly lower relative to a thermoset

Charles P. Rader

Advanced Elastomer Systems, L.P.

DK4036_book.fm Page 1 Monday, April 25, 2005 12:18 PM
© 2006 by Taylor & Francis Group, LLC
Figure 58.1 compares the generic classes of TPEs by performance and by cost. Thus, EAs have higher

Elastomeric Alloy Thermoplastic Elastomers

58

-3

These materials have been especially well received by the automotive industry, with typical uses being
hoses, jacketing, grommets, seals, convoluted boots, and weather-stripping. They are prime candidates
for under-the-hood uses, where the temperatures are progressively increasing.
EAs function nicely as a material for window glazing and expansion joints in architectural applications.
More than 50 major North American buildings have utilized the unique properties of EAs. Mechanical
rubber goods include those featuring a rubber article as a component part of a useful assembly. Typical
commercial uses of EAs in this area include household appliances, office equipment, toys and other
articles requiring the use of seals, boots, tubing, and bushings, and other rubber articles produced by
extrusion, injection molding, or blow molding.
EAs from EPDM rubber and polypropylene have excellent electrical properties — dielectric strength
resistivity, power factor, dielectric constant — that render them highly suitable for use as a primary
electrical insulator, as well as a jacketing material. Electrically conducting wire can be coated by crosshead
extrusion of an EA and can be used in automotive, appliance, construction, and many other applications.
The low toxicity of two-phase EAs recommends them highly for applications involving direct contact
with foods and potable water. These materials also offer much promise for medical applications embrac-
ing direct contact with pharmaceutical preparations to be taken orally or injected into the bloodstream.

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59

-1

59

Polyvinyl Chloride and
Its Copolymers in

Plastisol Coatings

59.1

59.2 Formulation

59-

1

59.3 Plastisol Manufacturing Procedures

59-

4

59.1 Introduction

PVC plastisols are liquid dispersion systems of polyvinyl chloride and/or PVC copolymer resins in
compatible plasticizers. The liquids vary in viscosity from thin milklike fluids to heavy pastes that have
the consistency of molasses.
The lowest viscosity products are generally used for spray coatings and some paper and fabric coatings,
while the higher viscosity products are often utilized in dipping, slush molding, rotocasting, and other
ore specialized procedures.

59.2 Formulation

Viscosity of plastisol is controlled by formulation techniques, and it is often kept low by the addition of
inactive diluents such as odorless mineral spirits. If more than minor amounts of diluents are used, the
product is often referred to as an organosol.
These products share a common compounding technology. The primary components are the disper-
sion-grade resin, plasticizers, PVC stabilizers (which are common to all PVC), and assorted fillers,
pigments, and a wide variety of additives to control properties of the product in storage, during process-

59.2.1 Resins

PVC dispersion resins are very fine particle size products made by emulsion polymerization and finished
by the spray drying technique. These paste resins are characterized by their molecular weight, particle
size, and shape. They are predominantly homopolymers, but there are also a wide variety of copolymers
made with polyvinyl acetate as the comonomer. The comonomer content will normally vary from 3 to
10%. Other comonomers are sometimes used.

Jesse Edenbaum

Consultant

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© 2006 by Taylor & Francis Group, LLC

Resins • Plasticizers • Solvents • Other Additives
Equipment • Quality Control • Coating Application •
Introduction 59-1
Continuous Thin Film Applications
ing, and in the finished state. A typical plastisol formulation is shown in Table 59.1.

60

-1

60

Polyvinyl Acetal Resins

60.1 Chemistry and Manufacture

60-

1
60.2 Availability, Economics

60-

1
60.3 Properties

60-

2

Surface Coating Applications

60-

9

References

60-

11

60.1 Chemistry and Manufacture

The polyvinyl acetals are a family of high molecular weight polymers prepared by the mineral acid
catalyzed acetalization of polyvinyl alcohol. The chemistry of preparation is outlined in Equation 60.1,
where R can be H or any of a wide variety of organic radicals.
While many polyvinyl acetals have been prepared,

1,2

the only commercially important polymers are
the formal (R

=

H) and the butyral (R

=

n

– C

3

H

7

), derived from the acetalization of polyvinyl alcohols
with formaldehyde and

n

-butyraldehyde, respectively. The generalized structure of the polyvinyl acetal
about 25,000 to 150,000 for the formal and from 40,000 to 250,000 K for the butyral, depending on
grade. The three chemical moieties are randomly distributed along the polymer chain. While simple in
concept, the actual commercial preparation of these polymers is quite complex, requiring many processing
steps. For the formal and the majority of the butyral resins currently of importance in the coating industry,
these steps include extensive solvent and by-product purification and recovery operations. A schematic
process flow diagram for the manufacture of a typical polyvinyl acetal, polyvinyl butyral (PVB), is shown

60.2 Availability, Economics

Monsanto is the only U.S. producer of polyvinyl formal, under the brand name of Formvar. The resins
are available in the United States as white to pale buff-colored, free-flowing powders, in fiber drums at
CH

2
—CH—CH
2
—CH
—
OH
—
OH
—
O
—
O
—
R
CH
CH
2
—CH—CH
2
—CH
+ RCHO + H
2
O
H
+

Thomas P. Blomstrom

Monsanto Chemical Company

DK4036_book.fm Page 1 Monday, April 25, 2005 12:18 PM
© 2006 by Taylor & Francis Group, LLC
Reactivity and Compatibility • Physical and Chemical
Polyvinyl Butyral • Polyvinyl Butyral Dispersions • Polyvinyl
Properties • Solution Viscosity • Plasticizers • Toxicology 4
Formal
60.4
molecule is shown in Figure 60.1. Molecular weights, weight average molecular weight (Mw), range from
in Figure 60.2.