ISO 14896:2006
(Main)Plastics — Polyurethane raw materials — Determination of isocyanate content
Plastics — Polyurethane raw materials — Determination of isocyanate content
ISO 14896:2006 specifies two methods for the measurement of the isocyanate content of aromatic isoocyanates used as polyurethane raw materials. Method A is primarily applicable to refined toluene diisocyanate (TDI), methylene-bis-(4-phenylisocyanate) (MDI) and their prepolymers. Method B is applicable to refined, crude or modified isocyanates derived from toluene diisocyanate, methylene-bis-(4-phenylisocyanate) and polymethylene polyphenylisocyanate. It can also be used for isomer mixtures of toluene diisocyanate, methylene-bis-(4-phenylisocyanate) and polymethylene polyphenylisocyanate. Other aromatic isocyanates may be analysed by this method if precautions are taken to verify suitability. It is not applicable to blocked isocyanates.
Plastiques — Matières premières des polyuréthannes — Détermination de la teneur en isocyanate
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Standards Content (Sample)
INTERNATIONAL ISO
STANDARD 14896
Second edition
2006-06-01
Plastics — Polyurethane raw materials —
Determination of isocyanate content
Plastiques — Matières premières des polyuréthannes — Détermination
de la teneur en isocyanate
Reference number
ISO 14896:2006(E)
©
ISO 2006
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ISO 14896:2006(E)
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ii © ISO 2006 – All rights reserved
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ISO 14896:2006(E)
Contents Page
Foreword. iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions. 2
4 Principle. 2
5 Application . 2
6 Interferences . 2
7 Sampling. 3
8 Test conditions . 3
9 Reagents. 3
10 Apparatus . 4
11 Method A — Toluene/dibutylamine with aqueous HCI . 4
12 Method B — Toluene/TCB/DBA with methanolic HCI . 7
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ISO 14896:2006(E)
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.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
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.
ISO 14896 was prepared by Technical Committee ISO/TC 61, Plastics, Subcommittee SC 12, Thermosetting
materials.
This second edition cancels and replaces the first edition (ISO 14896:2000), of which it constitutes a minor
revision the purpose of which was to combine the standard with its Technical Corrigendum
ISO 14896:2000/Cor.1:2005.
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INTERNATIONAL STANDARD ISO 14896:2006(E)
Plastics — Polyurethane raw materials — Determination of
isocyanate content
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
This lnternational Standard specifies two methods for the measurement of the isocyanate content of aromatic
isoocyanates used as polyurethane raw materials. Method A is primarily applicable to refined toluene
diisocyanate (TDI), methylene-bis-(4-phenylisocyanate) (MDI) and their prepolymers. Method B is applicable
to refined, crude or modified isocyanates derived from toluene diisocyanate, methylene-bis-
(4-phenylisocyanate) and polymethylene polyphenylisocyanate. It can also be used for isomer mixtures of
toluene diisocyanate, methylene-bis-(4-phenylisocyanate) and polymethylene polyphenylisocyanate. Other
aromatic isocyanates may be analysed by this method if precautions are taken to verify suitability. It is not
applicable to blocked isocyanates.
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 385, Laboratory glassware — Burettes
ISO 648, Laboratory glassware — One-mark pipettes
ISO 3696, Water for analytical laboratory use — Specification and test methods
ISO 4787, Laboratory glassware — Volumetric glassware — Methods for use and testing of capacity
ISO 4788, Laboratory glassware — Graduated measuring cylinders
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
ISO 14898:1999, Plastics — Aromatic isocyanates for use in the production of polyurethane — Determination
of acidity
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ISO 14896:2006(E)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
polyurethane
polymer prepared by the reaction of an organic di- or polyisocyanate with compounds containing two or more
hydroxyl groups
NOTE Polyurethanes may be thermosetting, thermoplastic, rigid or soft and flexible, cellular or non-cellular.
3.2
assay
percent by mass of a specific isocyanate present in a sample
3.3
isocyanate content
NCO content
percent by mass of the NCO groups present in a sample
3.4
amine equivalent
mass of sample that will combine with 1 gram-equivalent of dibutylamine
4 Principle
4.1 Method A
The isocyanate sample is reacted with an excess of dibutylamine in toluene to form the corresponding
substituted urea. After cooling to room temperature, acetone is added as a co-solvent, then the reaction
mixture is back-titrated with standardized aqueous HCI using potentiometric or colorimetric end point
determination.
4.2 Method B
The isocyanate sample is reacted with an excess of dibutylamine in a toluene/trichlorobenzene solvent to form
the corresponding substituted urea. After cooling to room temperature, the reaction mixture is diluted with
methanol and back-titrated potentiometrically or colorimetrically with methanolic hydrochloric acid.
5 Application
These test methods can be used for research or for quality control purposes to characterize isocyanates used
in polyurethane products.
6 Interferences
Phosgene, the carbamyl chloride of the isocyanate, hydrogen chloride and any other acidic or basic
compounds will interfere. In refined isocyanates, these impurities are usually present in such small amounts
that they do not affect the determination; however, some crude or modified isocyanates may contain acidities
of up to approximately 0,3 %, so the value reported for the NCO content of unrefined isocyanates should
preferably be designated as “corrected” or “uncorrected” for acidity.
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ISO 14896:2006(E)
7 Sampling
Since organic isocyanates react with atmospheric moisture, take special precautions in sampling (see
warning). Usual sampling methods (for example, sampling an open drum with a thief), even when conducted
rapidly, can cause contamination of the sample with insoluble ureas; therefore, blanket the sample with a dry
inert gas (e.g. nitrogen, argon or dried air) at all times.
WARNING — Organic isocyanates are hazardous when absorbed through the skin, or when the
vapours are breathed. Provide adequate ventilation and wear protective gloves and eyeglasses.
8 Test conditions
Since isocyanates react with moisture, keep the laboratory humidity low, preferably below 50 % relative
humidity.
9 Reagents
Use reagent-grade chemicals in all tests. Unless otherwise indicated, it is intended that all reagents shall
conform to the specifications of ISO 6353-1, ISO 63535-2 and ISO 6353-3. Other grades may be used,
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 3 water as defined in ISO 3696.
9.1 Acetone (method A).
9.2 Toluene, dried over type 4A molecular sieve.
9.3 di-n-butylamine solution, 1 mol/l (method A).
Dilute 129 g of di-n-butylamine to 1 litre with toluene.
9.4 di-n-butylamine solution, 2 mol/l (method B).
Dilute 258 g of di-n-butylamine to 1 litre with toluene.
9.5 Aqueous hydrochloric acid, 1 mol/l (method A).
Prepare 1 mol/l aqueous hydrochloric acid and standardize frequently enough to detect changes of
0,001 mol/l.
9.6 Methanolic hydrochloric acid, 1 mol/l (method B).
Prepare 1 mol/l hydrochloric acid in methanol and standardize frequently enough to detect changes of
0,001 mol/l.
NOTE In order to have homogeneous solutions, it is recommended that methanolic HCI be used in this procedure. If
desired, aqueous HCI can be used; however, turbidity will be encountered in some titrations. It is recommended that
200 ml to 250 rnl of methanol be added to the reacted product to minimize the formation of two layers. Experience has
shown that, if the mixtures are agitated vigorously, inhomogeneity can be tolerated without adversely affecting the results.
9.7 Bromophenol blue indicator solution, for colorimetric titration: 0,04 % aqueous solution of
bromophenol blue sodium salt, reagent grade, or 0,04 % solution of bromophenol blue in acetone.
9.8 1,2,4-Trichlorobenzene (TCB), dried over type 4A molecular sieve (method B).
9.9 Methanol (method B).
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ISO 14896:2006(E)
10 Apparatus
10.1 Potentiometric titrator or pH-meter, accurate to 0,1 mV or better, equipped with a pair of electrodes or
a combination glass-calomel electrode (filled with a 1 mol/l lithium chloride solution in methanol, or an
equivalent solution) and a piston burette having a 20 ml capacity.
10.2 Syringes, 2 ml and 5 ml, and syringes with a large orifice suitable for weighing v
...
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