The Specialty Chemicals Innovator铮?
TDS-237
Edition: January, 2002
Neutralizing Carbopol庐 and Pemulen庐 Polymers in
Aqueous and Hydroalcoholic Systems
Effect of pH on Viscosity
Carbopol polymers must be neutralized in order to 100,000
achieve maximum viscosity. Unneutralized dispersions
have an approximate pH range of 2.5-3.5 depending Carbopol庐 Ultrez鈩? 10
on the polymer concentration. The unneutralized
dispersions have very low viscosities, especially
庐
Carbopol ETD and Ultrez polymers. Once a Carbopol庐 ETD鈩? 2020
neutralizer is added to the dispersion, thickening
Brookfield Viscosity, cP, 20 rpm
gradually occurs as is demonstrated by Figure 1. 10,000
Optimum neutralization is achieved at a pH of Carbopol庐 ETD鈩? 2050
6.5-7.0, but is not necessary. As demonstrated by
the graph, high viscosities can be achieved in a
range of 5.0-9.0.
A common question is "what pH is correct for my
finished product?" The answer is that there is no
correct or incorrect pH. pH should be determined 1,000
by the desired attributes for a given application.
Viscosity begins to decrease after a pH of 9.0, and
will continue to decrease if the pH is increased. This
is due to the dampening of the electrostatic repulsion
caused by the presence of excess electrolytes. It is
possible to achieve high viscosity systems at pH
values below 5 and above 9, but the use level of 2 4 6 8 10 12 14
the Carbopol polymer must be increased. pH
Figure 1
Carbopol Polymers Viscosity vs. pH (0.5% Concentration)
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. .
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庐 Trademark of Noveon, Inc.
漏 Copyright 2002 Noveon, Inc.
2
Figure 4
Figure 2
Neutralization Ratio Chart
Schematic Depicting Molecule of Carbopol Polymer
in Coiled State
Neutralization
Ratio Base/
Trade Name CTFA Name Manufacturer
Carbopol庐
OH
OH Polymer
OH
O
C=O Sodium
=
NaOH (18%) 2.3/1.0
C C=O Hydroxide
Ammonia Ammonium
OH
O
0.7/1.0
C
= (28%) Hydroxide
=C
O
OH
Potassium
O=C KOH (18%) 2.7/1.0
Hydroxide
OH
C
=
OH L-Arginine Arginine Ajinomoto 4.5/1.0
O
Aminomethyl
AMP-95庐 Angus 0.9/1.0
Propanol
Tetrahydro-
Figure 3
Neutrol庐 TE xypropyl BASF 2.3/1.0
Diagram Depicting Molecule of Carbopol Polymer Ethylenediamine
in Uncoiled State
TEA (99%) Triethanolamine 1.5/1.0
Tris Amino庐
-- +
O NH 4 Tromethamine Angus 3.3/1.0
(40%)*
Ethomeen庐 PEG-15
C=O Akzo 6.2/1.0
C-25 Cocamine
Diisopropanol- Diisopropanol-
Dow 1.2/1.0
amine amine
C=O C=O Triisopropanol- Triisopropanol-
Dow 1.5/1.0
amine amine
+ -- + --
NH 4 O NH 4 O * NOTE: The 40% solution should be made from Tris Amino crystals from the manufacturer.
Do not use the pre-dispersed solution from the manufacturer as it contains many impurities.
Thickening Mechanism Common Neutralizers
Carbopol polymers as supplied are dry, tightly Figure 4 lists ten of the most common neutralizers
coiled acidic molecules. Once dispersed in water, used, the manufacturers of these neutralizers, and the
the molecules begin to hydrate and partially uncoil. appropriate ratio (as compared to one part of Carbopol
The most common way to achieve maximum polymers) to use to achieve exact neutralization at a
thickening from Carbopol polymers is by converting 庐
pH of 7.0. The chart is based on Carbopol Ultrez鈩?
the acidic Carbopol polymer to a salt. This is easily 10, Noveon, Inc.'s newest addition to the Carbopol
achieved by neutralizing the Carbopol polymer with polymer family, but is applicable to all Carbopol
a common base such as sodium hydroxide (NaOH) polymers because they all have the same equivalent
or triethanolamine (TEA). weight of 76 卤 4.
3
Figure 5 Hydroalcoholic Thickening
Recommended Neutralizers for Hydroalcoholic Systems
Ethanol and isopropanol can be thickened with
庐
Carbopol polymers. The critical factor is choosing
Up to % Alcohol Neutralizer
the correct neutralizer based on the amount of alcohol
that is to be gelled. If the wrong neutralizer is used,
20% Sodium Hydroxide
the salt of the Carbopol polymer will precipitate out
because it is no longer soluble in the hydroalcoholic
30% Potassium Hydroxide
blend. Figure 5 gives recommended neutralizers for
various alcohol levels.
60% Triethanolamine
60% Tris Amino
AMP-95庐
80%
90% Neutrol TE
90% Diisopropanolamine
90% Triisopropanolamine
>90% Ethomeen C-25
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