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Ref. No.: IS0 / R 307 - 1963 (E)
IS0
I NT ERN AT I ON AL ORGAN I ZATl O N FOR STAND AR D I Z AT I O N
IS0 RECOMMENDATION
L
R 307
L
PLASTICS
DETERMINATION OF THE VISCOSITY NUMBER
OF POLYAMIDES IN DILUTE SOLUTION
1st EDITION
May 1963
COPYRIGHT RESERVED
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 oniy valid standard is the national standard of that country.
hinted 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 307, Determination of the Viscosity Number of Polyamides
in Dilute Solution, was drawn up by Technical Committee ISO/TC 61, Plastics, the Secre-
tariat of which is held by the American Standards Association, Inc. (ASA).
Work on this question by the Technical Committee began in 1956 and led, in 1959, to
the adoption of a Draft IS0 Recommendation.
In October 1960, this Draft IS0 Recommendation (No. 381) was circulated to all the
IS0 Member Bodies for enquiry. It was approved, subject to a few modifications of an
editorial nature, by the following Member Bodies :
Australia India Romania
Austria Israel Spain
Belgium Italy Sweden
Chile Japan Switzerland
Czechoslovakia Netherlands Turkey
New Zealand United Kingdom
Germany
Hungary Poland U.S.A.
U.S.S.R.
One Member Body opposed the approval of the Draft:
France.
The Draft IS0 Recommendation was then submitted by correspondence to the IS0
Council, which decided, in May 1963, to accept it as an IS0 RECOMMENDATION.
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IS0 / R 307 - 1- (E)
IS0 Recommendation R 307 May 1963
PLASTICS
DETERMINATION OF THE VISCOSITY NUMBER
OF POLYAMIDES IN DILUTE SOLUTION
1. SCOPE
1.1 This method of test is designed to determine the viscosity number (see Appendix A, page 8)
of a solution in formic acid or metacresol of polyamides. The method applies only to
those resins that give stable solutions and reproducible results under the conditions of test
described below. The times of flow of the solvent and of a solution containing 0.005 g/ml of
polyamide are measured at 25 “C by conventional methods, and the viscosity number is
calculated from these measurements and from the known concentration of the solution.
Density and kinetic energy corrections are small in this method and are not applied.
1.2 If monomer * is known to be present in the sample, the amount should be determined by the
relevant IS0 method ** and reported. The presence of monomer affects considerably
the determination of viscosity number of certain types of polyamides. If the sample
contains an additive or a filler, which would affect the viscosity measurement, it should be
removed by a procedure agreed between the contracting parties.
1.3 This method is meant to give an insight into the molecular structure of polyamides and for
the purpose of comparing different types. For control purposes in the manufacture of
polyamides or for specifications, viscosity is normally determined in concentrated solution
in accordance with the relevant IS0 Recommendation.***
*
In this text, monomer is understood as ‘‘ monomer and low molecular mass polymer ” of the relevant IS0 Recom-
mendation (see below **).
**
IS0 Recommendation under preparation, Plastics-Determination of the Percentage of Monomer and Low Molecular
at present Draft IS0 Recommendation No. 512.
Weight Polymer in Polyamide Resins,
***
IS0 Recommendation under preparation, Plastics-Determination of the “Relative Viscosity ” of Polyamide Resins
in Concentrated Solution, at present Draft IS0 Recommendation No. 513.
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IS0 / R 307 - 1963 (E)
2. APPARATUS
The apparatus consists of the following:
(a) Automatic pipette, 50 ml and
(6) Flat-bottomedflask, 150 ml, with ground-glass stopper, or
Volumetric flask, 50 ml, with ground-glass stopper.
(c) Filter.funne1 of sintered glass with a porosity of 40 to 90 pm,* or
Conical sieve of stainless steel with apertures about 0.075 mm2,
(d) Bath, maintained at 25 it 0.05 OC.
(e) Viscometer of suspended level Ubbelohde type; its essential dimensions are shown in the
figure (page 61,
alternatively, any other viscometer that can be shown to give the same results.
(f) Balance, to weigh to O.Oo0 1 g.
(g) Stop-watch reading to 0.1 second.
(h) Burette.
(i) Bottle of brown glass connected to an automatic burette and fitted with a calcium chloride
tube on the air inlet.
Possibly means for drying (see clause 4.1).
3. SOLVENTS AND CHEMICALS
The following solvents and chemicals are required :
(1) Formic acid, containing 90 f 0.2 per cent by mass of chemically pure formic acid, the
remainder being water (see Appendix B, page 8),** or
Metacresol, freshly distilled, melting point 11 to 12 OC.
(2) Cleaning liquids (distilled water, concentrated sulphuric acid, saturated aqueous solution of
potassium dichromate, ethanol, acetone).
4. PREPARATION OF SAMPLE
4.1 The sample should be in the form of small pieces or powder. The water content, determined
in accordance with the relevant IS0 Recommendation,*** should not exceed 0.4 per cent.
4.2 Alternatively, if the water content exceeds 0.4 per cent and is known, the mass of resin
taken should be adjusted to give the specified weight of dry material.
*
M. Bechtold, Zeitschrift für Physikalische Chemie, 60 (1907), 257 and 64 (1908), 328.
**
Formic acid should be used whenever possible, i.e. when the resin is soluble in this solvent.
***
See IS0 Recommendation R 62, Plastics-Determination of Water Absorption.
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IS0 / R 307 - 1963 (E)
5. PROCEDURE
5.1 Before it is first used, after discordant readings and at regular intervals during use, the
viscometer (e) is cleaned first with the solvent (1) or (2) and successively with water and
with a mixture of equal volumes of concentrated sulphuric acid and a saturated solution
of potassium dichromate (3) in water. After rinsing with distilled water, the viscometer should
be washed with 95 to 96 per cent ethanol, followed by acetone, and dried by drawing through
it a stream of air free from dust. Between
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