EN ISO 2554:1998

Plastics - Unsaturated polyester resins - Determination of hydroxyl value (ISO 2554:1997)

Kunststoffe - Ungesättigte Polyesterharze - Bestimmung der Hydroxylzahl (ISO 2554:1997)

Diese Internationale Norm Beschreibt ein Verfahren zur Bestimmung der Hydroxylzahl von ungesättigten Polyesterharzen. Dieses Verfahren bestimmt den Unterschied zwischen der Hydroxylzahl und der Säurezahl. Es ist deshalb erforderlich, die Säurezahl gesondert zu bestimmen, um die Hydroxylzahl berechnen zu können. ANMERKUNG 1: Die Hydroxylzahl von gesättigten Polyesterharzen (z. B. Polyesterharze, die für die Herstellung von Polyurethanen und Polyweichmachern benutzt werden) und von bestimmten Typen von Alkydharzen kann auch nach diesem Verfahren bestimmt werden.

Plastiques - Résines de polyesters non saturés - Détermination de l'indice d'hydroxyde (ISO 2554:1997)

La présente Norme internationale prescrit une méthode pour la détermination de l'indice d'hydroxyle des résines de polyesters non saturés. En fait, la méthode détermine la différence entre l'indice d'hydroxyle et l'indice d'acide ; il est donc nécessaire d'avoir déterminé par ailleurs l'indice d'acide total du produit pour calculer l'indice d'hydroxyle.  
NOTE 1 L'indice d'hydroxyle de résines de polyesters saturés (par exemple les résines de polyesters utilisées pour la fabrication des polyuréthanes et les plastifiants polymériques) et de certains types de résines alkydes, peut également être déterminé par cette méthode.

Polimerni materiali - Nenasičene poliestrske smole - Določanje hidroksilnega števila (ISO 2554:1997)

General Information

• Status: Published
• Publication Date: 21-Jul-1998
• Withdrawal Date: 30-Jan-1999
• ICS: 83.080.10 - Thermosetting materials
• Technical Committee: CEN/TC 249 - Plastics
• Drafting Committee: CEN/TC 249/SC 1/WG 13 - Thermosets
• Current Stage: 6060 - Definitive text made available (DAV) - Publishing
• Start Date: 22-Jul-1998
• Completion Date: 22-Jul-1998
• Ref Project: SIST EN ISO 2554:2000 - Plastics - Unsaturated polyester resins - Determination of hydroxyl value (ISO 2554:1997)

Overview

EN ISO 2554:1998 is an international standard published by CEN that specifies the method for determining the hydroxyl value of unsaturated polyester resins. The hydroxyl value is a critical parameter representing the amount of hydroxyl groups present in the resin, which impacts its reactivity and suitability for various applications such as composites, coatings, and adhesives. This standard ensures consistent, reliable measurement by detailing the acetylation and titration procedures required for accurate hydroxyl value determination.

Key Topics

• Scope and Purpose
  The standard focuses on measuring the hydroxyl value in unsaturated polyester resins by acetylation and titration, including steps to account for acid values that may influence results. Though designed primarily for unsaturated polyester resins, the method can also apply to saturated polyester and certain alkyd resins.

• Terminology

  • Hydroxyl value: Milligrams of potassium hydroxide (KOH) required to neutralize the acetic acid that reacts with 1 gram of resin.
  • Acid value: Milligrams of KOH needed to neutralize all acidic components under test conditions.
  • Total acid value: Neutralization value of all acid-terminated groups and free acids, determined separately per ISO 2114.

• Methodology
  The procedure involves:

  • Acetylating hydroxyl groups in the resin by reaction with acetic anhydride, catalyzed by toluene-4-sulfonic acid.
  • Hydrolyzing excess acetic anhydride with a pyridine/water mixture, followed by titration of resulting acetic acid with methanolic potassium hydroxide.
  • Calculating hydroxyl value from titration data and accounting for total acid value.

• Reagents and Equipment
  Includes high-purity reagents such as anhydrous ethyl acetate, toluene-4-sulfonic acid, pyridine/water mixture, and standard methanolic KOH solution. Key apparatus includes a magnetic stirrer, water bath, pipettes, burettes, and optional potentiometric titration equipment for improved precision, especially with colored samples.

• Precision and Reporting
  The method's precision is under evaluation through interlaboratory studies, with future updates expected. Test reports must reference the standard, sample details, results, any deviations, and test conditions.

Applications

EN ISO 2554:1998 is vital for:

• Quality Control in the production of unsaturated polyester resins to ensure expected reactivity and performance.
• Material Development by resin manufacturers aiming to tailor resin properties through hydroxyl content adjustments.
• Polyurethane and Alkyd Resin Testing since the method is suitable for certain saturated polyesters and alkyds, supporting broader applications like coatings and plasticizers.
• Standards Compliance for industrial users seeking to meet international requirements for resin characterization in composites, laminates, and advanced plastics.

Related Standards

• ISO 2114:1996 – Plastics – Unsaturated polyester resins – Determination of partial acid value and total acid value, a complementary standard required for determining acid values used in EN ISO 2554 calculations.
• ISO 3696:1987 – Water for analytical laboratory use, defines water purity necessary for reagent preparation and testing accuracy.

By following EN ISO 2554:1998, laboratories and manufacturers can reliably determine the hydroxyl value of unsaturated polyester resins, supporting improved product consistency and better control over resin properties critical for high-performance plastic components.

Standards Content (Sample)

SLOVENSKI STANDARD
01-maj-2000
3ROLPHUQLPDWHULDOL1HQDVLþHQHSROLHVWUVNHVPROH'RORþDQMHKLGURNVLOQHJD
ãWHYLOD,62
Plastics - Unsaturated polyester resins - Determination of hydroxyl value (ISO
2554:1997)
Kunststoffe - Ungesättigte Polyesterharze - Bestimmung der Hydroxylzahl (ISO
2554:1997)
Plastiques - Résines de polyesters non saturés - Détermination de l'indice d'hydroxyde
(ISO 2554:1997)
Ta slovenski standard je istoveten z: EN ISO 2554:1998
ICS:
83.080.10 Duromeri Thermosetting materials
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

INTERNATIONAL
IS0
STANDARD
Second edition
1997-03-01
Plastics - Unsaturated polyester resins -
Determination of hydroxyl value
Plastiques - Msines
polyesters non sat&s - D&ermina tion de
I’indice d’hydroxyle
Reference number
IS0 2554: 1997(E)
IS0 2554: 1997(E)
Foreword
IS0 (the International Organization for Standardization) is a worldwide federation of national standards bodies (IS0
member bodies). The work of preparing International Standards is normally carried out through IS0 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. IS0 collaborates closely with the International Electrotechnical
Commission (IEC) on all matters of electrotechnical standardization.
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.
International Standard IS0 2554 was prepared by Technical Committee ISO/TC 61, Plastics, Subcommittee SC 12,
Thermosetting materials.
This second edition cancels and replaces the first edition (IS0 2554:1974), of which it constitutes a minor (editorial)
revision.
0 IS0 1997
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced
or utilized in any form or by any means, electronic or mechanical, including photocopying and
microfilm, without permission in writing from the publisher.
International Organization for Standardization
Case postale 56 l CH-1211 Geneve 20 l Switzerland
Internet central @ iso.ch
x.400 c=ch; a=400net; p=iso; o=isocs; s=central
Printed in Switzerland
ii
IS0 2554: 1997(E)
INTERNATIONAL STANDARD o IS0
Plastics - Unsaturated polyester resins - Determination of
hydroxyl value
1 Scope
This International Standard specifies a method for determining the hydroxyl value of unsaturated polyester resins.
In fact, this method determines the difference between the hydroxyl value and the acid value; it is therefore
necessary to determine the total acid value separately, in order to calculate the hydroxyl value.
NOTE 1 The hydroxyl value of saturated polyester resins (for example, polyester resin used for the manufacture of
polyurethanes and polymeric plasticizers) and of certain types of alkyd resins may also be determined by this method.
2 Normative references
The following standards contain provisions which, through reference in this text, constitute provisions of this
International Standard. At the time of publication, the editions indicated were valid. All standards are subject to
revision, and parties to agreements based on this International Standard are encouraged to investigate the
possibility of applying the most recent editions of the standards indicated below. Members of IEC and IS0 maintain
registers of currently valid International Standards.
IS0 2114:1996, Plastics - Unsaturated polyester resins - Determination of partial acid value and total acid value.
- Specification and test methods.
IS0 3696: 1987, Water for analytical laboratory use
3 Definitions
For the purposes of this International Standard, the following definitions apply:
3.1 hydroxyl value: The number of milligrams of potassium hydroxide necessary to neutralize the acetic acid
which will combine, by acetylation, with 1 g of an unsaturated polyester resin.
3.2 acid value: The number of milligrams of potassium hydroxide required to neutralize 1 g of a test sample under
the test conditions.
3.3 total acid value: The acid value corresponding to the neutralization of all carboxyl-terminated groups and free
acids and free anhydrides of a polyester.
4 Principle
The hydroxyl groups in the resin are acetylated by reacting an ethyl acetate solution of the resin with acetic
anhydride in the presence of toluene-4-sulfonic acid catalyst. The excess acetic anhydride is hydrolysed by a
pyridine/water mixture and the resultant acetic acid is titrated with methanolic potassium hydroxide solution.
0 IS0
IS0 2554: 1997(E)
hyd rid e groups which exist in the resin are also neutralized by the
In this titration, the free acid and free an
potassi urn hydroxide.
The hydroxyl value is finally calculated by taking into account the total acid value determined separately by
IS0 2114.
5 Reagents
During the analysis, use only reagents of recognized analytical grade and water of
...