EN ISO 8988:2006

SLOVENSKI STANDARD
01-december-2006
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SIST EN ISO 8988:1999
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Plastics - Phenolic resins - Determination of hexamethylenetetramine content - Kjeldahl
method, perchloric acid method and hydrochloric acid method (ISO 8988:2006)
Kunststoffe - Phenolharze - Bestimmung des Hexamethylentetramingehaltes - Kjeldahl-
Verfahren, Perchlorsäureverfahren und Salzsäureverfahren (ISO 8988:2006)
Plastiques - Résines phénoliques - Détermination de la teneur en
hexaméthylenetétramine - Méthode Kjeldahl, méthode a l'acide perchlorique et méthode
a l'acide chlorhydrique (ISO 8988:2006)
Ta slovenski standard je istoveten z: EN ISO 8988:2006
ICS:
83.080.10 Duromeri Thermosetting materials
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN ISO 8988
NORME EUROPÉENNE
EUROPÄISCHE NORM
September 2006
ICS 83.080.10 Supersedes EN ISO 8988:1997
English Version
Plastics - Phenolic resins - Determination of
hexamethylenetetramine content - Kjeldahl method, perchloric
acid method and hydrochloric acid method (ISO 8988:2006)
Plastiques - Résines phénoliques - Détermination de la Kunststoffe - Phenolharze - Bestimmung des
teneur en hexaméthylènetétramine - Méthode Kjeldahl, Hexamethylentetramingehaltes - Kjeldahl-Verfahren,
méthode à l'acide perchlorique et méthode à l'acide Perchlorsäureverfahren und Salzsäureverfahren (ISO
chlorhydrique (ISO 8988:2006) 8988:2006)
This European Standard was approved by CEN on 26 August 2006.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national
standards may be obtained on application to the Central Secretariat or to any CEN member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation
under the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the official
versions.
CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France,
Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania,
Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
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COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36  B-1050 Brussels
© 2006 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 8988:2006: E
worldwide for CEN national Members.

Foreword
This document (EN ISO 8988:2006) has been prepared by Technical Committee ISO/TC 61
"Plastics" in collaboration with Technical Committee CEN/TC 249 "Plastics", the secretariat of
which is held by IBN.
This European Standard shall be given the status of a national standard, either by publication of
an identical text or by endorsement, at the latest by March 2007, and conflicting national
standards shall be withdrawn at the latest by March 2007.

This document supersedes EN ISO 8988:1997.

According to the CEN/CENELEC Internal Regulations, the national standards organizations of
the following countries are bound to implement this European Standard: Austria, Belgium,
Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary,
Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland,
Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.

Endorsement notice
The text of ISO 8988:2006 has been approved by CEN as EN ISO 8988:2006 without any
modifications.
INTERNATIONAL ISO
STANDARD 8988
Third edition
2006-09-01
Plastics — Phenolic resins —
Determination of hexamethylenetetramine
content — Kjeldahl method, perchloric
acid method and hydrochloric acid
method
Plastiques — Résines phénoliques — Détermination de la teneur en
hexaméthylènetétramine — Méthode Kjeldahl, méthode à l'acide
perchlorique et méthode à l'acide chlorhydrique

Reference number
ISO 8988:2006(E)
©
ISO 2006
ISO 8988:2006(E)
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ii © ISO 2006 – All rights reserved

ISO 8988:2006(E)
Contents Page
Foreword. iv
1 Scope . 1
2 Normative references . 1
3 Kjeldahl method. 1
4 Perchloric acid method . 3
5 Hydrochloric acid method . 5
6 Test report . 7

ISO 8988:2006(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 8988 was prepared by Technical Committee ISO/TC 61, Plastics, Subcommittee SC 12, Thermosetting
materials.
This third edition cancels and replaces the second edition (ISO 8988:1995), which has been technically
revised to include a hydrochloric acid method.

iv © ISO 2006 – All rights reserved

INTERNATIONAL STANDARD ISO 8988:2006(E)

Plastics — Phenolic resins — Determination of
hexamethylenetetramine content — Kjeldahl method, perchloric
acid method and hydrochloric acid method
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 International Standard specifies three methods for the determination of the hexamethylenetetramine
(“hexa”) content of phenolic resins. The three methods are equivalent. The Kjeldahl method described in
Clause 3 is not applicable if there are other components containing nitrogen in the phenolic resin. The
perchloric acid method and the hydrochloric acid method described in Clause 4 and Clause 5, respectively,
are only applicable if there are no other basic or acidic additives in the resin. If the resin contains additives
which can be oxidized by perchloric acid, only the hydrochloric acid method (Clause 5) is applicable.
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
3 Kjeldahl method
WARNING — For safety reasons, the Kjeldahl determination must be carried out in a well ventilated
fume cupboard.
3.1 General
This clause specifies a method for the determination of total nitrogen, expressed as hexamethylenetetramine,
in phenolic resins. The method is applicable to hexamethylenetetramine contents of W 0,5 % (by mass).
3.2 Principle
The hexamethylenetetramine in a test portion is converted to ammonium bisulfate by decomposition in hot
concentrated sulfuric acid in the presence of a catalyst.
The ammonium bisulfate is converted to sodium sulfate and ammonia by reaction with sodium hydroxide.
The ammonia is distilled off and collected in hydrochloric acid.
The excess hydrochloric acid is titrated with a standard volumetric solution of sodium hydroxide using a
colorimetric indicator.
ISO 8988:2006(E)
3.3 Reagents
During the analysis, unless otherwise stated, use only reagents of recognized analytical grade, free of
nitrogen, and only distilled water or water of equivalent purity.
3.3.1 Sulfuric acid, concentrated.
3.3.2 Kjeldahl catalytic mixture, consisting of 97 g of sodium sulfate decahydrate (Na SO ·10H O), 1,5 g
2 4 2
of copper sulfate pentahydrate (CuSO ·5H O) and 1,5 g of selenium (Se).
4 2
3.3.3 Sodium hydroxide, 30 % (by mass) solution.
3.3.4 Hydrochloric acid, c(HCl) = 0,10 mol/l.
3.3.5 Sodium hydroxide, standard volumetric solution, c(NaOH) = 0,10 mol/I.
3.3.6 Mixed indicator, solution.
Dissolve 60 mg of methyl red and 40 mg of methylene blue in 100 ml of ethanol.
3.4 Apparatus
Ordinary laboratory apparatus, plus the following:
3.4.1 Kjeldahl flask, capacity 250 ml or 300 ml, for the digestion.
3.4.2 Distillation apparatus (various models are available commercially).
3.4.3 Burette, capacity 50 ml, graduated in 0,1 ml steps, conforming to ISO 385.
3.4.4 Analytical balance, accurate to 1 mg.
3.4.5 Silicon carbide crystals, for use as boiling chips.
3.5 Procedure
3.5.1 Digestion
Weigh 1 g to 2 g of phenolic resin to the nearest 1 mg into a Kjeldahl flask (3.4.1). Add 5 g of the catalytic
mixture (3.3.2) and 25 ml of concentrated sulfuric acid (3.3.1). Heat carefully until the colour of the mixture
changes from black or amber to clear. When the mixture is clear, increase the rate of heating and heat for
5 min beyond the time of the colour change; the mixture may possibly boil. Allow the digested liquid to cool
almost to room temperature, just short of solidification. Add carefully 100 ml of water and transfer the solution
quantitatively into the flask of the distillation apparatus, rinsing with water. Add a few silicon carbide crystals
(3.4.5) to prevent bumping and two drops of mixed indicator solution (3.3.6). Add 30 % (by mass) NaOH
solution (3.3.3) to this solution until it is basic. Then distill over the ammonia given off, together with water
vapour, into a receiver containing 50 ml of hydrochloric acid (3.3.4). Continue the distillation until about 300 ml
of water has been collected.
3.5.2 Titration
When the distillation is completed, add a few drops of mixed indicator solution (3.3.6) to the contents of the
receiver and titrate the excess hydrochloric acid with sodium hydroxide solution (3.3.5), using the burette
(3.4.3).
2 © ISO 2006 – All rights reserved

ISO 8988:2006(E)
3.6 Expression of results
The hexamethylenetetramine content, expressed as a percentage by mass, is given by the formula:
0,35 (VV− )
m
where
V is the volume, in millilitres, of hydrochloric acid (3.3.4) in the receiver of the distillation apparatus;
V is the volume, in millilitres, of sodium hydroxide solution (3.3.5) used in the back-titration;
m is the mass, in grams, of the test portion.
3.7 Reproducibility
The results are reproducible to within 0,30 % (by mass) hexamethylenetetramine.
3.8 Number of determinations
Carry out the determination in duplicate. If the results differ by more than 5 %, repeat the determination, again
in duplicate. If not, calculate the arithmetic mean of the two individual results.
4 Perchloric acid method
4.1 Genera
...