oSIST prEN ISO 844:2025

SLOVENSKI STANDARD
01-april-2025
Trdi penjeni polimerni materiali (trde pene) - Ugotavljanje lastnosti stiskanja
(ISO/DIS 844:2025)
Rigid cellular plastics - Determination of compressive properties (ISO/DIS 844:2025)
Harte Schaumstoffe - Bestimmung der Druckeigenschaften (ISO/DIS 844:2025)
Plastiques alvéolaires rigides - Détermination des caractéristiques de compression
(ISO/DIS 844:2025)
Ta slovenski standard je istoveten z: prEN ISO 844
ICS:
83.100 Penjeni polimeri Cellular materials
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
International
Standard
ISO/DIS 844
ISO/TC 61/SC 10
Rigid cellular plastics —
Secretariat: SCC
Determination of compressive
Voting begins on:
properties
2025-02-04
Plastiques alvéolaires rigides — Détermination des
Voting terminates on:
caractéristiques de compression
2025-04-29
ICS: 83.100
THIS DOCUMENT IS A DRAFT CIRCULATED
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IS THEREFORE SUBJECT TO CHANGE
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Reference number
ISO/DIS 844:2025(en)
DRAFT
ISO/DIS 844:2025(en)
International
Standard
ISO/DIS 844
ISO/TC 61/SC 10
Rigid cellular plastics —
Secretariat: SCC
Determination of compressive
Voting begins on:
properties
Plastiques alvéolaires rigides — Détermination des
Voting terminates on:
caractéristiques de compression
ICS: 83.100
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
This document is circulated as received from the committee secretariat.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
© ISO 2025
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
STANDARDS MAY ON OCCASION HAVE TO
ISO/CEN PARALLEL PROCESSING
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BE CONSIDERED IN THE LIGHT OF THEIR
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Published in Switzerland Reference number
ISO/DIS 844:2025(en)
ii
ISO/DIS 844:2025(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 . 3
6.1 Testing machine .3
6.2 Devices for measuring displacement and force .4
6.2.1 Displacement .4
6.2.2 Force .4
6.2.3 Calibration . . .4
6.3 Devices for measuring the dimensions of the test specimens .4
7 Test specimens . 4
7.1 Dimensions .4
7.2 Preparation .5
7.3 Number .5
7.4 Conditioning.5
8 Procedure . 5
9 Expression of results . 6
9.1 General .6
9.2 Compressive strength and compressive strains .7
9.2.1 Compressive strength .7
9.2.2 Nominal compressive strain (procedure A) .7
9.2.3 Compressive strain (procedure B) .8
9.3 Compressive stress at 10 % nominal compressive strain (procedure A) .8
9.4 Nominal compressive modulus (procedure A) .8
9.5 Compressive modulus (procedure B) .8
10 Precision . 8
10.1 Procedure A .8
10.2 Procedure B .9
11 Test report . 10
Annex A (Informative) Remarks about the determination of the compressive modulus.11
Bibliography .13

iii
ISO/DIS 844:2025(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 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 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 compared to the previous edition are as follows:
— “Compression” changed to “compressive” throughout the document, including the title.
— The scope changed to include details of Procedure A and Procedure B.
— “Relative deformation” changed “compressive strain.”
— “Nominal relative deformation” changed “nominal compressive strain”.
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/DIS 844:2025(en)
Introduction
For the determination of compressive stresses, it is common practice to apply an overall 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 standard describes this procedure as Procedure A, which determines the nominal properties.
Procedure B, on the other hand, is used to determine conventional properties, as described below.
Procedure A employs relative plate displacement for the determination of compressive properties. It shall be
used to determine:
— compressive strength and the corresponding nominal compressive strain;
— compressive stress at 10 % nominal compressive strain;
— nominal compressive modulus.
Procedure B employs displacement measuring devices directly positioned on the specimen (contact or
optical extensometer) or similar devices that measure the specimen displacement. Procedure B shall be
used to determine:
— compressive strength and the corresponding compressive strain;
— compressive modulus
v
DRAFT International Standard ISO/DIS 844:2025(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, while Procedure B uses an extensometer and
determines the conventional properties.
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 amendments) applies.
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 — Part 1:
Tension/compression testing machines — Calibration and verification of the force-measuring system
ISO 9513, Metallic materials — Calibration of extensometer systems used in uniaxial testing
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
nominal compressive strain
ε
C
ratio of the reduction (in relation to its initial value) in thickness of the test specimen
Note 1 to entry: It is expressed as a percentage.
Note 2 to entry: ε is the nominal compressive strain at σ (see 3.3).
Cm m
Note 3 to entry: Procedure A applies.
3.2
compressive strain
ε
ratio of the reduction (in relation to its initial value) of extensometer gauge length
Note 1 to entry: It is expressed as a percentage.

ISO/DIS 844:2025(en)
Note 2 to entry: ε is the compressive strain at σ (see 3.3).
m m
Note 3 t
...