ISO 25761:2014

INTERNATIONAL ISO
STANDARD 25761
Second edition
2014-03-01
Plastics — Polyols for use in the
production of polyurethanes —
Determination of basicity (total amine
value), expressed as percent nitrogen
Plastiques — Polyalcools utilisés pour la production de
polyuréthannes — Détermination de la basicité (valeur totale
d’amines) en pourcentage d’azote
Reference number
©
ISO 2014
© ISO 2014
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ii © ISO 2014 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Sampling . 2
6 Apparatus . 2
7 Interference . 2
8 Reagents . 2
9 Procedure. 3
10 Expression of results . 4
11 Precision and bias . 4
11.1 General . 4
11.2 Precision . 5
11.3 Bias . 5
12 Test report
................................................................................................................................................................................................................... 5
Annex A (informative) Determination of the factor F for 0,1 mol/l perchloric acid in acetic acid .6
Bibliography . 7
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of any
patent rights identified during the development of the document will be in the Introduction and/or on
the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the meaning of ISO specific terms and expressions related to conformity
assessment, as well as information about ISO’s adherence to the WTO principles in the Technical Barriers
to Trade (TBT) see the following URL: Foreword - Supplementary information.
The committee responsible for this document is ISO/TC 61, Plastics, Subcommittee SC 12, Thermosetting
materials.
This second edition cancels and replaces the first edition (ISO 25761:2008), which has been technically
revised.
iv © ISO 2014 – All rights reserved

Introduction
Polyurethanes are produced by the catalysed reaction of isocyanates with polyols. The basicity of the
polyol employed affects the rate of reaction and speed of cure of the product. It is therefore necessary to
determine the basicity in order to predict reactivity and monitor product quality.
INTERNATIONAL STANDARD ISO 25761:2014(E)
Plastics — Polyols for use in the production of
polyurethanes — Determination of basicity (total amine
value), expressed as percent nitrogen
SAFETY STATEMENT — Persons using this document should be familiar with normal laboratory
practice, if applicable. This document does not purport to address all of the safety concerns, if
any, associated with its use. It is the responsibility of the user to establish appropriate safety and
health practices and to ensure compliance with any regulatory requirements.
1 Scope
The method specified in this International Standard measures the basic constituents in polyols that
are soluble in glacial acetic acid and reactive with perchloric acid. Samples containing 0,3 % to 10 % of
nitrogen have been evaluated by this method. The method is applicable to amine-based polyols, polyether
polyols and polyether polyol blends that are used in polyurethane reactions. The results are measures of
batch-to-batch uniformity and may be used to estimate reactivity in polyurethane reactions.
It is also permissible to express the results in equivalents of base per gram of sample.
NOTE This method is technically equivalent to that in ASTM D 6979.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 1042, Laboratory glassware — One-mark volumetric flasks
ISO 4788, Laboratory glassware — Graduated measuring cylinders
ISO 3696, Water for analytical laboratory use — Specification and test methods
ISO 6353-1, Reagents for chemical analysis — Part 1: General test methods
ISO 6353-2, Reagents for chemical analysis — Part 2: Specifications — First series
ISO 6353-3, Reagents for chemical analysis — Part 3: Specifications — Second series
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
polyol
polymer based on ethylene oxide and/or propylene oxide which contains two or more hydroxyl groups
3.2
polyurethane
polymer prepared by the reaction of an organic di- or polyisocyanate with a compound containing two
or more hydroxyl groups
3.3
percent nitrogen
quantity of perchloric-acid-titratable base in a sample, expressed as a mass percentage of nitrogen
3.4
alkalinity
quantity of perchloric-acid-titratable base in a sample, expressed as mg of KOH/g of sample
3.5
total amine value
quantity of perchloric-acid-titratable base in a sample, identified only as amines and expressed as mg of
KOH/g of sample
4 Principle
A test portion of the sample is dissolved in glacial acetic acid. The resulting single-phase solution is
titrated at room temperature to a potentiometric end point with a standardized solution of perchloric
acid in acetic acid. The result is reported as percent nitrogen or mg of KOH/g of sample.
5 Sampling
Draw samples from a well-mixed vessel into a thoroughly cleaned and dry borosilicate-glass container
(soft-glass containers are not acceptable). If sampling from a line or valve, flush the line thoroughly with
the product before starting to draw the sample. Seal the sample until analysis.
6 Apparatus
6.1 One-mark volumetric flask, of capacity 1 000 ml conforming to ISO 1042.
6.2 Graduated measuring cylinder, of capacity 100 ml and 500 ml conforming to ISO 4788.
6.3 Precision balance, accurate to 0,1 mg or better.
6.4 Potentiometric titrator, capable of determining multiple end points, equipped with a pair of
electrodes or a combination glass calomel electrode, a 20 ml burette and a recorder.
7 Interference
Any acidic or basic materials inadvertently introduced into the sample will cause errors in the analysis.
Any material capable of serving as a buffer may interfere with the analysis by obscuring the titration
end point.
8 Reagents
Unless otherwise indicated, it is intended that all reagents shall conform to the specifications of
ISO 6353-1, ISO 6353-2 and ISO 6353-3, as applicable. Other grades may be used, however, provided that
it is first determined that the reagent is of sufficiently high purity to permit its use without lessening the
accuracy of the determination.
Unless otherwise indicated, references to water shall be understood to mean grade 2 water as defined
in ISO 3696.
8.1 Glacial acetic acid.
8.2 Acetic anhydride.
8.3 Perchloric acid, nominal concentration 70 %.
2 © ISO 2014 – All rights reserved

8.4 Perchloric acid in acetic acid, concentration 0,10 mol/l.
One way of preparing the 0,10 mol/l perchloric acid in acetic acid is as follows. In a 1 000 ml volumetric
flask, mix 8,7 ml of perchloric acid (8.3) with 500 ml of glacial acetic acid (8.1). Add 25 ml of acetic
anhydride (8.2) and dilute to volume with glacial acetic acid.
WARNING — Perchloric acid is extremely irritating to the skin, eyes and mucous membranes,
highly toxic via oral and inhalation routes, and can form explosive mixtures when mixed with
carbonaceous material or allowed to dry. Concentrated perchloric acid should only be used in a
hood approved for perchloric acid use. Chemically resistant gloves should be worn. In the event
of skin contact, wash with soap and water. Goggles or safety glasses with side shields should be
worn. In the event of eye contact, flush with copious amounts of water for 15 min. In the event of
inhalation, move the victim to an uncontaminated area. In the event of ingestion, do not induce
vomiting. For all exposures, seek professional medical advice.
It is strongly recommended that reference articles on perchloric acid safety be consulted to determine
safe-handling and clean-up procedures (see References [1] to [6] and references cited therein).
9 Procedure
9.1 Weigh a test portion of the sample into a suitable container, calculating the mass of the test portion
as follows:
M′ = 2/P
where
M′ is the mass of the test portion, in g;
P is the expected percent nitrogen content of the sample.
For test portion masses below 10,0 g, record the mass to the nearest 0,1 mg; for test portion masses
greater than 10,0 g, record the mass to the nearest 0,01 g.
9.2 Add 100 ml of glacial acetic acid and stir gently until the test portion has dissolved completely.
If necessary, the mixture can be heated gently until the test portion has completely dissolved.
9.3 Titrate the test solution potentiometrically using a potentiometric titrator (6.4) with 0,10 mol/l
perchloric acid (8.4) through the end point which occurs at about 600 mV.
Colorimetric end point determinations can also be used. Suitable indicators are patent blue VF or crystal
violet. Typically, 10 dr
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