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IS0
I N TER NAT1 O N AL O R GAN 1 ZATl O N F O R STAN DAR D I ZATl O N
IS0 RECOMMENDATION
R 600
PLASTICS
DETERMINATION OF THE VISCOSITY RATIO OF POLYAMIDES
IN CONCENTRATED SOLUTION
1st EDITION
August 1967
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The copyright of IS0 Recommendations and IS0 Standards
belongs to IS0 Member Bodies. Reproduction of these
documents, in any country, may be authorized therefore only
by the national standards organization of that country, being
a member of ISO.
For each individual country the only valid standard is the national standard of that country.
Printed in Switzerland
Also issued in French and Russian. Copies to be obtained through the national standards organizations.
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BRIEF HISTORY
The IS0 Recommendation R 600, Plastics - Determination of the viscosity ratio of
polyamides in concentrated solution, was drawn up by Technical Committee ISO/TC 61, Plastics,
the Secretariat of which is held by the United States of America Standards Institute (USASI).
Work on this question by the Technical Committee began in 1960 and led, in 1961, to the
adoption of a Draft IS0 Recommendation.
This first Draft IS0 Recommendation (NO 513) was circulated in June 1962 to all the
IS0 Member Bodies for enquiry. As the results of this consultation were not considered satis-
factory, the Technical Committee presented a second Draft IS0 Recommendation which was
circulated to all the Member Bodies in July 1964 and which was approved, subject to a few
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modifications of an editorial nature by the following Member Bodies :
Austria
India South Africa
Belgium Italy Rep. of
Canada Japan Sweden
Chile Korea, Rep. of U.A.R.
Czechoslovakia
Netherlands United Kingdom
Denmark New Zealand U.S.A.
Finland Poland U. S. S.R.
Germany Romania
One Member Body opposed the approval of the Draft:
France
The second Draft IS0 Recommendation was then submitted by correspondence to the
IS0 Council, which decided, in August 1967, to accept it as an IS0 RECOMMENDATION.
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ISO/R 600 - 1967 (E)
IS0 Recommendation R 600 August 1967
PLASTICS
DETERMINATION OF THE VISCOSITY RATIO OF POLYAMIDES
IN CONCENTRATED SOLUTION
1. SCOPE
1.1 This IS0 Recommendation describes a test method for determining the viscosity ratio of
a solution of polyamides in formic acid. The method is applicable to those polyamides only that
are soluble and do not degrade in formic acid in the specified conditions and which give repro-
ducible results under the conditions of test described below. The times of flow of the solvent and
of a solution containing 8.4 % by mass (1 1 g/100 mi) of polyamide in the solvent are measured
at 25 “C by conventional methods and the viscosity ratio is calculated from these measurements.
Mathematical corrections for kinetic energy are small in this method and are not applied.
1.2 If a substantial amount of monomer” is known to be present in the sample, the amount
should be determined in accordance with IS0 Recommendation R 599* and indicated in
the test report. The presence of monomer affects considerably the determination of viscosity
ratio of certain types of polyamides. If the sample contains an additive or filler which would
affect the viscosity measurement, it should be removed by a procedure agreed between the
contracting parties.
1.3 This method is intended for use in specifications for polyamides for the purpose of comparing
different types or for control purpose during manufacture. To get an insight into the molecular
structure of polyamides, viscosity is normally determined in dilute solution in accordance
with IS0 Recommendation R 307, Determination of the viscosity number of polyamides in
dilute solution.
* In this text, monomer is understood as “monomer and low molecular mass polymer” in accordance with IS0 Recom-
mendation R 599, Plastics - Determination of the percentage of extractable materials in polyamides.
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IÇO/R WO - 1967 (E)
Dimensions in millimetres
J
\
FIGURE - Viscorneter for viscosity ratio
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ISO/R WO - 1967 (E)
2. REAGENTS
2.1 The solvent and chemicals should consist of the following.
2.1.1 Formic acid solvent, containing 90 f 0.2% by mass of chemically pure formic acid,
the remainder being water (see Annex A, page 9).
2.1.2 Glycerol, analytical grade.
2.1.3 Cleaning liquids, (distilled water, concentrated sulphuric acid, saturated aqueous solution
of potassium dichromate, chemically pure hydrochloric acid, ethanol and acetone).
2.2 Safety measures
When cleaning viscometers which have previously been used for viscosity determinations,
care should be taken to ensure that the viscometers are first washed out with the solvent and
with water before attempting to clean them with concentrated sulphuric acid and potassium
dichromate mixture.
3. APPARATUS
The apparatus should consist of the following:
(a) Pycnometer.
(b) Water-bath, maintained at 25 f 0.1 OC.
(c) Viscometer, type Ostwald, with a flow time for water of 10 to 15 seconds (for measuring
the viscosity of the polyamide solution) (see Figure, page 4).
(d) Viscometer, type Ostwald, with a flow time for water of 100 to 200 seconds (for measuring
the viscosity of formic acid).
(For these two viscometers any other type that can be shown to give the same results
may be used with appropriate modification of procedure).
(e) Stopwatch, reading to 0.1 second.
(f) Pipette, 7 ml type Ostwald.
(g) Burette.
(h) Flask, 150 mi, fitted with ground-glass stopper.
(i) Brown glass bottle, connected to an automatic burette and fitted with a calcium chloride
tube on the air inlet.
(j) Balance, to weigh to 0.0001 g.
(k) Suitable means for reducing coarse materials to a finer state of division.
(I) Mechanical stirrer.
(m) Oven, maintained at 125 OC or vacuum oven (2 mm mercury) at 100 OC.
(n) Sieve, stainless steel, mesh openings 3.15 mm.
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ISO/R 600 - 1967 (E)
4. PREPARATION OF SAMPLE
The sample should be in the form of small pieces or powder that pass through the sieve with mesh
openings 3.15 mm. The water content, determined in accordance with IS0 Recommendation R . . . *
should be lower than 1 .O % and, if necessary, the sample should be dried by a suitable method.
For instance, if the polymer does not contain sublimable monomer, it may be dried in a vacuum
oven at a temperature not higher than 80 "C for about 24 hours.
5. PROCEDURE
5.1 Calculate the constants of the viscometers with the aid of mixtures of glycerol and water of
known viscosity (see Annex B, page 10).
5.2 Dilute the formic acid with distilled water to a concentration of 90 it 0.2% formic acid
(see Annex A, page 9).
5.3 Before it is first used and after discordant readings if any, the viscometer should be cleaned
at first with the solvent and then successively with water and with a mixture of equal volumes
of concentrated sulphuric acid and a saturated solution of potassium dichromate in water.
After rinsing with distilled water it should be washed with 95 to 96% ethanol, followed by
acetone and dried by drawing through it a stream of air free from dust. Between successive
determinations, the viscometer should be washed several times
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