SIST EN ISO 844:2026

• Abstract:

  This document specifies methods for determining the compressive strength, the corresponding compressive strain, the compressive stress at 10 % nominal compressive strain, and the compressive modulus of rigid cellular plastics.; Two procedures are specified. Procedure A and Procedure B.; Procedure A utilizes the compression plate displacement for the nominal property determination. It is used to determine:; compressive strength and the corresponding nominal compressive strain;; compressive stress at 10 % nominal compressive strain;; nominal compressive modulus.; Procedure B uses an extensometer and determines the conventional properties. It is used to determine:; compressive strength and the corresponding compressive strain;; compressive modulus.

• Status: Published
• Public Enquiry End Date: 28-Apr-2025
• Publication Date: 21-Jul-2026
• ICS: 83.100 - Cellular materials
• Technical Committee: IPMA - Polimer materials and products
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 21-Jul-2026
• Due Date: 25-Sep-2026
• Completion Date: 22-Jul-2026
• Ref Project: EN ISO 844:2026 - Rigid cellular plastics - Determination of compressive properties (ISO 844:2026)

• Refers: SIST ISO 1923:1996 - Cellular plastics and rubbers -- Determination of linear dimensions
• Effective Date: 22-Jul-2026
• Referred By: SIST EN 17333-4:2020 - Characterization of One Component Foam - Part 4: Mechanical strength
• Effective Date: 15-Jul-2026
• Referred By: SIST EN 17415-1:2020 - District cooling pipes - Bonded single pipe systems for directly buried cold water networks - Part 1: Factory made pipe assembly of steel or plastic service pipe, polyurethane thermal insulation and a casing of polyethylene
• Effective Date: 15-Jul-2026
• Referred By: SIST EN 253:2020 - District heating pipes - Bonded single pipe systems for directly buried hot water networks - Factory made pipe assembly of steel service pipe, polyurethane thermal insulation and a casing of polyethylene
• Effective Date: 15-Jul-2026
• Referred By: SIST EN ISO 5139:2023 - Dentistry - Polymer-based composite machinable blanks (ISO 5139:2023)
• Effective Date: 28-Jan-2026
• Revised: SIST EN ISO 844:2021 - Rigid cellular plastics - Determination of compression properties (ISO 844:2021)
• Effective Date: 18-Jan-2023

Overview

SIST EN ISO 844:2026 - Rigid Cellular Plastics: Determination of Compressive Properties (ISO 844:2026) provides standardized methods for measuring the compressive properties of rigid cellular plastics, commonly known as rigid foams. These properties - compressive strength, compressive strain, compressive stress at 10% nominal compressive strain, and compressive modulus - are critical for quality assurance, product design, and comparison purposes in plastics engineering. This standard is essential for manufacturers and testing laboratories that work with rigid cellular plastics in various industries, ensuring consistent, reliable, and comparable test results.

The document specifies two procedures:

• Procedure A: Uses compression plate displacement for determining nominal properties.
• Procedure B: Utilizes an extensometer for conventional measurement of compressive properties.

By clearly outlining apparatus requirements, specimen preparation, test procedures, and reporting formats, SIST EN ISO 844:2026 supports compliance, reliability, and traceability across diverse applications, playing a key role in the characterization of rigid cellular plastic materials.

Key Topics

• Compressive Strength and Modulus: The standard details how to determine the maximum compressive force a material can sustain relative to its size (strength) and its stiffness under load (modulus).
• Compressive Strain: Both nominal (based on overall displacement) and conventional (measured with extensometer) compressive strains are defined and calculated.
• Test Specimen Preparation: Guidance ensures that sampling, dimensions, and conditioning of test specimens meet the necessary consistency for accurate comparison.
• Apparatus Requirements: Describes the need for suitable testing machines, extensometers, and calibration routines according to ISO 7500-1 and ISO 9513.
• Two Distinct Testing Procedures:
  • Procedure A: Focuses on nominal property determination using plate displacement, measuring strength, strain, compressive stress at 10% strain, and nominal modulus.
  • Procedure B: Employs specimen-attached extensometers for conventional strength and modulus measurements.
• Reporting and Documentation: Specifies required details for test reports, including specimen identification, test conditions, all measured values, and any deviations from the methods.
• Precision and Repeatability: Results of interlaboratory tests are included to establish method precision and facilitate reproducibility across different laboratories.

Applications

This international standard is widely used in fields where rigid foam performance under compression is critical, such as:

• Building and Construction: Evaluation of thermal insulation materials, sandwich panels, and structural foams to validate their load-bearing capabilities.
• Automotive Industry: Testing lightweight foam components for energy absorption and structural integrity.
• Packaging: Qualification of foam impact-absorbing and load-bearing packaging materials.
• Manufacturing Quality Control: Routine assessment of foam batches to ensure compliance with product specifications.
• Product Development: Comparing new material formulations based on compressive behavior.

Adhering to ISO 844 ensures objectivity and comparability in compressive property data, underpinning product safety, regulatory compliance, and innovation.

Related Standards

For comprehensive evaluation and consistent testing of plastics and cellular materials, the following standards are relevant:

• ISO 291: Plastics - Standard atmospheres for conditioning and testing
• ISO 1923: Cellular plastics and rubbers - Determination of linear dimensions
• ISO 7500-1: Metallic materials - Calibration and verification of static uniaxial testing machines
• ISO 9513: Metallic materials - Calibration of extensometer systems used in uniaxial testing
• ISO 5725-2: Accuracy (trueness and precision) of measurement methods and results

Using SIST EN ISO 844:2026 in conjunction with these related standards ensures comprehensive compliance, accuracy, and reliability in the testing and characterization of rigid cellular plastics and other polymeric materials.

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Keywords: rigid cellular plastics, compressive strength, compressive modulus, ISO 844, strength testing, foam testing, polymer standards, quality assurance, mechanical properties plastics, testing procedures for rigid foam

SLOVENSKI STANDARD
01-september-2026
Trdi penjeni polimerni materiali (trde pene) - Ugotavljanje lastnosti stiskanja (ISO
844:2026)
Rigid cellular plastics - Determination of compressive properties (ISO 844:2026)
Harte Schaumstoffe - Bestimmung der Druckeigenschaften (ISO 844:2026)
Plastiques alvéolaires rigides - Détermination des caractéristiques de compression (ISO
844:2026)
Ta slovenski standard je istoveten z: EN ISO 844:2026
ICS:
83.100 Penjeni polimeri Cellular materials
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 844
EUROPEAN STANDARD
NORME EUROPÉENNE
July 2026
EUROPÄISCHE NORM
ICS 83.100 Supersedes EN ISO 844:2021
English Version
Rigid cellular plastics - Determination of compressive
properties (ISO 844:2026)
Plastiques alvéolaires rigides - Détermination des Harte Schaumstoffe - Bestimmung der
caractéristiques de compression (ISO 844:2026) Druckeigenschaften (ISO 844:2026)
This European Standard was approved by CEN on 23 June 2026.

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 CEN-CENELEC Management Centre 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 CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2026 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 844:2026 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 844:2026) 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 SIS.
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 January 2027, and conflicting national standards shall
be withdrawn at the latest by January 2027.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN ISO 844:2021.
Any feedback and questions on this document should be directed to the users’ national standards
body/national committee. A complete listing of these bodies can be found on the CEN website.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and the
United Kingdom.
Endorsement notice
The text of ISO 844:2026 has been approved by CEN as EN ISO 844:2026 without any modification.

International
Standard
ISO 844
Eighth edition
Rigid cellular plastics —
2026-06
Determination of compressive
properties
Plastiques alvéolaires rigides — Détermination des
caractéristiques de compression
Reference number
ISO 844:2026(en) © ISO 2026
ISO 844:2026(en)
© ISO 2026
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: [phone]
Email: [e-mail]
Website: www.iso.org
Published in Switzerland
ii
ISO 844:2026(en)
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols . 3
5 Principle . 3
6 Apparatus . 4
6.1 Testing machine .4
6.2 Devices for measuring displacement and force .4
6.2.1 Displacement .4
6.2.2 Force .4
6.2.3 Calibration . . .5
6.3 Devices for measuring the dimensions of the test specimens .5
7 Test specimens . 5
7.1 Dimensions .5
7.2 Preparation .5
7.3 Number .5
7.4 Conditioning.5
8 Procedure . 6
9 Expression of results . 6
9.1 General .6
9.2 Compressive strength and compressive strains .8
9.2.1 Compressive strength .8
9.2.2 Nominal compressive strain (procedure A) .8
9.2.3 Compressive strain (procedure B) .8
9.3 Compressive stress at 10 % nominal compressive strain (procedure A) .8
9.4 Modulus.8
9.4.1 General .8
9.4.2 Nominal compressive modulus (procedure A) .9
9.4.3 Compressive modulus (procedure B) .9
10 Precision . 9
10.1 Procedure A .9
10.2 Procedure B .10
11 Test report . 10
Annex A (informative) Extensometer for Procedure B .12
Bibliography .13

iii
ISO 844:2026(en)
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 document 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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and expressions
related to conformity assessment, as well as information about ISO's adherence to the World Trade
Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 61, Plastics, Subcommittee SC 10, Cellular
plastics, in collaboration with the European Committee for Standardization (CEN) Technical Committee
CEN/TC 249, Plastics, in accordance with the Agreement on technical cooperation between ISO and CEN
(Vienna Agreement).
This eighth edition cancels and replaces the seventh edition (ISO 844:2021), which has been technically
revised.
The main changes are as follows:
— the term “compression” changed to “compressive” throughout the document, including the title;
— the scope has been modified to include details of Procedure A and Procedure B;
— “relative deformation” has been changed to “compressive strain”;
— “nominal relative deformation” has been changed to “nominal compressive strain”;
— “necking” has been changed to the more descriptive “force-drop”.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.

iv
ISO 844:2026(en)
Introduction
For the determination of compressive properties, it is common practice to apply a uniform compressive
deformation to a standard test specimen, especially for quality assurance. However, the test specimen has
a complex and inhomogeneous deformation state, under compression, which is not subjected to further
analysis in such an evaluation. Measurement results are, therefore, not easily transferable to other test
specimens or products. This document describes Procedure A, which determines the nominal compressive
properties. Procedure B determines conventional compressive properties.
Procedure A employs relative plate displacement for the determination of compressive properties.
Procedure B employs displacement measuring devices directly positioned on the specimen (contact or
optical extensometer) or similar devices that measure the specimen displacement.

v
International Standard ISO 844:2026(en)
Rigid cellular plastics — Determination of compressive
properties
1 Scope
This document specifies methods for determining the compressive strength, the corresponding compressive
strain, the compressive stress at 10 % nominal compressive strain, and the compressive modulus of rigid
cellular plastics.
Two procedures are specified. Procedure A and Procedure B.
Procedure A utilizes the compression plate displacement for the nominal property determination. It is used
to determine:
— compressive strength and the corresponding nominal compressive strain;
— compressive stress at 10 % nominal compressive strain;
— nominal compressive modulus.
Procedure B uses an extensometer and determines the conventional properties. It is used to determine:
— compressive strength and the corresponding compressive strain;
— compressive modulus.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any ame
...