ISO/FDIS 844

Rigid cellular plastics — Determination of compressive properties

This document specifies methods for determining the compressive strength and corresponding relative deformation, the compressive stress at 10 % relative deformation, and the compressive modulus of rigid cellular plastics.

Plastiques alvéolaires rigides — Détermination des caractéristiques de compression

Le présent document spécifie des méthodes permettant de déterminer la résistance à la compression et la déformation relative correspondante, la contrainte en compression correspondant à 10 % de déformation relative et le module en compression des plastiques alvéolaires rigides.

General Information

• Status: Not Published
• ICS: 83.100 - Cellular materials
• Technical Committee: ISO/TC 61/SC 10 - Cellular plastics
• Drafting Committee: ISO/TC 61/SC 10 - Cellular plastics
• Current Stage: 5020 - FDIS ballot initiated: 2 months. Proof sent to secretariat
• Start Date: 27-Mar-2026
• Completion Date: 27-Mar-2026

Relations

• Consolidates: FprEN ISO 844 - Rigid cellular plastics - Determination of compressive properties (ISO/FDIS 844:2026)
• Effective Date: 12-Feb-2026
• Consolidates: ISO 18675:2022 - Dentistry — Machinable ceramic blanks
• Effective Date: 17-Dec-2022
• Revises: ISO 844:2021 - Rigid cellular plastics — Determination of compression properties
• Effective Date: 03-Dec-2022

Overview

ISO/FDIS 844:2026 – Rigid cellular plastics - Determination of compressive properties is an international standard developed by ISO Technical Committee 61, Subcommittee 10. This standard specifies reliable and reproducible test methods to determine the compressive properties of rigid cellular plastics, including compressive strength, compressive strain, compressive stress at 10% nominal compressive strain, and compressive modulus. It is designed to support quality control, research, and product development by providing standardized procedures for testing these essential material properties.

With two complementary procedures (A and B), ISO/FDIS 844 covers both nominal and conventional compressive property measurements, ensuring wide applicability across different testing needs.

Key Topics

• Scope and Purpose

  • Covers the determination of compressive properties for rigid cellular plastics, such as compressive strength, strain, and modulus.
  • Defines two procedures for measurement:
    • Procedure A: Uses compression plate displacement for nominal properties.
    • Procedure B: Employs an extensometer for conventional properties.

• Test Methods

  • Specifies requirements for testing machines, specimen preparation, measurement devices, and calibration procedures.
  • Outlines preferred specimen dimensions and preparation to ensure consistency and comparability.
  • Details step-by-step instructions for conducting tests, from specimen placement to data recording.

• Critical Definitions

  • Establishes terms like compressive strength, compressive strain, nominal compressive modulus, and related measurement parameters to promote uniform understanding.

• Reporting and Results

  • Provides guidelines for recording and reporting results, including averages, individual data if variations exceed 10%, testing environment, and any deviations from the standard method.
  • Includes reporting of compressive strength, modulus, stress at 10% strain, and associated strains.

Applications

• Quality Control: Manufacturers regularly use ISO/FDIS 844 to ensure that rigid cellular plastic products meet specified compressive strength and deformation criteria during production.
• Product Development: Material scientists and product engineers utilize the standard’s testing procedures to compare new formulas or manufacturing techniques in terms of mechanical performance.
• Comparative Evaluation: The standardized methodology allows different organizations, laboratories, and product lines to objectively compare the compressive properties of rigid foams, insulation products, and structural plastics.
• Compliance and Certification: Third-party certification bodies often require compliance with ISO/FDIS 844 as part of product performance validation for markets that demand quality assurance and regulatory adherence.

Industries commonly applying ISO/FDIS 844 include:

• Building and construction (insulation panels, structural foams)
• Automotive and aerospace (lightweight, impact-absorbing materials)
• Packaging (protective foam materials)
• Appliance manufacturing (thermal insulation components)

Related Standards

Utilizing ISO/FDIS 844 effectively often involves reference to additional standards, including:

• ISO 291: Plastics - Standard atmospheres for conditioning and testing (for specimen conditioning requirements)
• ISO 1923: Cellular plastics and rubbers - Determination of linear dimensions (for dimensional measurement instruments)
• ISO 7500-1: Metallic materials - Calibration and verification of static uniaxial testing machines (relevant to force measurements)
• ISO 9513: Metallic materials - Calibration of extensometer systems used in uniaxial testing (pertinent for displacement measurement, particularly for Procedure B)
• ISO 5725-2: Accuracy (trueness and precision) of measurement methods and results (cited for repeatability and reproducibility analyses)

ISO/FDIS 844:2026 is essential for anyone involved in the specification, production, or use of rigid cellular plastics, ensuring test results are accurate, comparable, and fit for purpose. For further detail and implementation, always reference the current official ISO document.

Standards Content (Sample)

FINAL DRAFT
International
Standard
ISO/TC 61/SC 10
Rigid cellular plastics —
Secretariat: SCC
Determination of compressive
Voting begins on:
properties
2026-03-27
Plastiques alvéolaires rigides — Détermination des
Voting terminates on:
caractéristiques de compression
2026-05-22
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO­
ISO/CEN PARALLEL PROCESSING LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
Reference number
FINAL DRAFT
International
Standard
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
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT,
WITH THEIR COMMENTS, NOTIFICATION OF ANY
RELEVANT PATENT RIGHTS OF WHICH THEY ARE AWARE
AND TO PROVIDE SUPPOR TING DOCUMENTATION.
© ISO 2026
IN ADDITION TO THEIR EVALUATION AS
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO­
ISO/CEN PARALLEL PROCESSING
LOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE
the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below
TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL
or ISO’s member body in the country of the requester.
TO BECOME STAN DARDS TO WHICH REFERENCE MAY BE
MADE IN NATIONAL REGULATIONS.
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 Reference number
ii
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
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
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
FINAL DRAFT International Standard ISO/FDIS 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 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 terminology 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
decrease in thickness per unit original thickness h 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
decrease in length per unit original gage length l
o
Note 1 to entry: It is expressed as a percentage.
Note 2 to entry: ε is the compressive strain at σ (see 3.3).
m m
Note 3 to entry: Procedure B applies.
3.3
compressive strength
σ
m
maximum compressive force F divided by the initial cross-sectional area A of the test specimen when the
m 0
ε and the ε , respectively, < 10 %
C
Note 1 to entry: It is expressed in megapascals (MPa).
3.4
compressive stress at 10 % nominal compressive strain
σ
...

ISO/TC 61/SC 10/WG 12
Secretariat: SCC
Date: 2026-xx-xx03-13
Rigid cellular plastics — Determination of compressive properties
Plastiques alvéolaires rigides — Détermination des caractéristiques de compression
FDIS stage
TThhiis drs draafftt i is s susubbmmiitttteed d ttoo aa ppaarraallellel l vvoottee i inn IISSOO,, CCEEN.N.

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'sISO’s member body in the country of the requester.
ISO Copyright Officecopyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: + 41 22 749 01 11
Email: E-mail: [e-mail]
Website: www.iso.org
Published in Switzerland.
ii
Contents Page
Foreword . iv
Introduction . v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols . 3
5 Principle . 4
6 Apparatus . 4
6.1 Testing machine . 4
6.2 Devices for measuring displacement and force . 5
6.3 Devices for measuring the dimensions of the test specimens . 5
7 Test specimens . 5
7.1 Dimensions . 5
7.2 Preparation . 6
7.3 Number . 6
7.4 Conditioning . 6
8 Procedure . 6
9 Expression of results . 7
9.1 General . 7
9.2 Compressive strength and compressive strains . 8
9.3 Compressive stress at 10 % nominal compressive strain (procedure A) . 9
9.4 Modulus . 9
10 Precision . 10
10.1 Procedure A . 10
10.2 Procedure B . 11
11 Test report . 11
Annex A (informative) Extensometer for Procedure B . 13
Bibliography . 15

iii
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
Introduction
For the determination of compressive properties, it is common practice to apply ana 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
FINAL DRAFT International Standard ISO/FDIS 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 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 terminologicalterminology 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 3.1
nominal compressive strain
εC
decrease in thickness per unit original thickness h of the test specimen
Note 1 to entry: It is expressed as a percentage.
Note 2 to entry: εCm is the nominal compressive strain at σm (see 3.33.3).).
Note 3 to entry: Procedure A applies.
3.2 3.2
compressive strain
ε
decrease in length per unit original gage length l
o
Note 1 to entry: It is expressed as a percentage.
Note 2 to entry: ε is the compressive strain at σ (see 3.33.3).).
m m
Note 3 to entry: Procedure B applies.
3.3 3.3
compressive strength
σ
m
maximum compressive force F divided by the initial cross-sectional area A of the test specimen when the ε
m 0
and the ε , respectively, < 10 %
C
Note 1 to entry: It is expressed in megapascals (MPa).
3.4 3.4
compressive stress at 10 % nominal compressive strain
σ
ratio of the compressive force F at 10 % nominal compressive strain ε to the initial cross-sectional area
10 C10
A of the test specimen
Note 1 to entry: It is expressed in megapascals (MPa).
Note 2 to entry: Procedure A applies
3.5 3.5
nominal compressive modulus
EC
difference in compressive stress divided by the difference in corresponding nominal compressive strain below
the nominal proportional limit
Note 1 to entry: It is expressed in megapascals (MPa).
Note 2 to entry: Procedure A applies.
3.6 3.6
compressive modulus
E
difference in compressive stress divided by the difference in corresponding compressive strain below the
proportional limit
Note 1 to entry: It is expressed in megapascals (MPa).
Note 2 to entry: Procedure B applies.
3.7 3.7
nominal proportional limit
X
Ce
upper displacement limit of the linear part of the force -nominal displacement curve
Note 1 to entry: It is expressed in millimetres (mm).
Note 2 to entry: Procedure A applies.
3.8 3.8
proportional limit
X
e
upper displacement limit of the linear part of the force–displacement curve
Note 1 to entry: It is expressed in millimetres (mm).
Note 2 to entry: Procedure B applies.
4 Symbols
Symb Definition Unit
ol
A initial cross-sectional area square millimetres
E compressive modulus megapascals
E nominal compressive modulus megapascals
C
Fe force at proportional limit newtons
F force at nominal proportional limit newtons
Ce
Fm maximum force newtons
F force at 10 % nominal compressive strain newtons
h0 initial thickness of test specimen millimetres
l initial gage length of the extensometer millimetres
o
Ra compression plate surface roughness micrometres
t compression plate thickness millimetres
X proportional limit millimetres
e
XCe nominal proportional limit millimetres
X displacement at maximum force millimetres
m
XCm nominal displacement at maximum force millimetres
X displacement at 10 % nominal compressive strain millimetres
C10
Symb Definition Unit
ol
εm compressive strain at compressive strength percent
ε nominal compressive strain at compressive strength percent
Cm
εC10 10 % nominal compressive strain percent
σ compressive stress at proportional limit megapascals
e
σm compressive strength megapascals
σ compressive stress at 10 % nominal compressive strain megapascals
5 Principle
A compressive force is applied perpendicular to the faces of the test specimen positioned between two rigid
plates using a constant displacement loading. Nominal compressive properties are determined from the
stress-strain data produced using the relative plate displacement as the displacement indicator. In contrast,
compressive properties are determined with an extensometer that provides a direct measurement of the test
specimen deformation.
6 Apparatus
6.1 Testing
...