EN ISO 3451-1:2026

• Abstract:

  This document specifies general methods, with suitable test conditions, for the determination of the ash of a range of plastics. The particular conditions chosen can be included in the specifications for the plastic material in question.; Particular conditions applicable to poly(alkylene terephthalate) materials, unplasticized cellulose acetate, polyamides and poly(vinyl chloride) plastics, including some specific filled, glass-fibre-reinforced and flame-retarded materials, are specified in ISO 3451-2, ISO 3451-3, ISO 3451-4 and ISO 3451-5.

• Status: Published
• Publication Date: 02-Jun-2026
• ICS: 83.080.01 - Plastics in general
• Technical Committee: CEN/TC 249 - Plastics
• Current Stage: 6060 - Definitive text made available (DAV) - Publishing
• Start Date: 03-Jun-2026
• Completion Date: 03-Jun-2026
• Ref Project: SIST EN ISO 3451-1:2026 - Plastics - Determination of ash - Part 1: General methods (ISO 3451-1:2026)

• Replaces: EN ISO 3451-1:2019 - Plastics - Determination of ash - Part 1: General methods (ISO 3451-1:2019)
• Effective Date: 18-Dec-2024
• Refers: ISO 472:2013 - Plastics — Vocabulary
• Effective Date: 15-Jul-2026
• Referred By: EN 13494:2002 - Thermal insulation products for building applications - Determination of the tensile bond strength of the adhesive and of the base coat to the thermal insulation material
• Effective Date: 10-Jun-2026
• Referred By: EN 14758-1:2023 - Plastics piping systems for non-pressure underground drainage and sewerage - Polypropylene with mineral modifiers (PP-MD) - Part 1: Specifications for pipes, fittings and the system
• Effective Date: 10-Jun-2026
• Referred By: EN 13598-1:2020 - Plastics piping systems for non-pressure underground drainage and sewerage - Unplasticized poly(vinyl chloride) (PVC-U), polypropylene (PP) and polyethylene (PE) - Part 1: Specifications for ancillary fittings and shallow chambers
• Effective Date: 10-Jun-2026
• Referred By: EN 1852-1:2018+A1:2022 - Plastics piping systems for non-pressure underground drainage and sewerage - Polypropylene (PP) - Part 1: Specifications for pipes, fittings and the system
• Effective Date: 10-Jun-2026
• Referred By: EN 1451-1:2017 - Plastics piping systems for soil and waste discharge (low and high temperature) within the building structure - Polypropylene (PP) - Part 1: Specifications for pipes, fittings and the system
• Effective Date: 10-Jun-2026
• Referred By: EN 18120-12:2026 - Packaging - Design for recycling of plastic packaging - Part 12: Recyclability evaluation process for plastic packaging - Protocols for PE and PP rigid packaging
• Effective Date: 10-Jun-2026
• Referred By: EN 17152-1:2019 - Plastics piping systems for non-pressure underground conveyance and storage of non-potable water - Boxes used for infiltration, attenuation and storage systems - Part 1: Specifications for storm water boxes made of PP and PVC-U
• Effective Date: 10-Jun-2026
• Referred By: EN 15345:2007 - Plastics - Recycled Plastics - Characterisation of Polypropylene (PP) recyclates
• Effective Date: 10-Jun-2026
• Referred By: EN 1852-1:2018 - Plastics piping systems for non-pressure underground drainage and sewerage - Polypropylene (PP) - Part 1: Specifications for pipes, fittings and the system
• Effective Date: 10-Jun-2026
• Referred By: EN 18120-15:2026 - Packaging - Design for recycling of plastic packaging - Part 15: Recyclability evaluation process for plastic packaging - Protocols for EPS packaging
• Effective Date: 10-Jun-2026
• Referred By: EN 15334:2007 - Sanitary appliances - Methacrylic dispersions of high filler content
• Effective Date: 10-Jun-2026
• Referred By: EN 13476-3:2018 - Plastics piping systems for non-pressure underground drainage and sewerage - Structured-wall piping systems of unplasticized poly(vinyl chloride) (PVC-U), polypropylene (PP) and polyethylene (PE) - Part 3: Specifications for pipes and fittings with smooth internal and profiled external surface and the system, Type B
• Effective Date: 10-Jun-2026
• Referred By: EN 15814:2011+A2:2014 - Polymer modified bituminous thick coatings for waterproofing - Definitions and requirements
• Effective Date: 10-Jun-2026

EN ISO 3451-1:2026 is a CEN European Standard that adopts ISO 3451-1:2026 for plastics. It specifies general methods for determining ash in a range of plastics, with suitable test conditions, for laboratories and other users who need a comparable ash result for a material specification.

What does EN ISO 3451-1:2026 specify?

EN ISO 3451-1:2026 specifies general methods for determining the ash of plastics and the test conditions used to do so. It also points users to the material-specific parts of the ISO 3451 series when a plastic type needs special conditions.

The document is organized into clauses on:

• scope
• normative references
• terms and definitions
• principle
• reagents
• apparatus
• procedure
• number of tests
• expression of results
• precision
• test report

The scope names poly(alkylene terephthalate) materials, unplasticized cellulose acetate, polyamides and poly(vinyl chloride) plastics as examples of materials covered in the related parts of the series.

What are the key requirements of EN ISO 3451-1:2026?

EN ISO 3451-1:2026 gives five main ways to determine ash - methods A, B, C, D and E - and requires the user to choose the method and temperature to match the plastic and its additives. In practice, that choice affects both the result and whether the test is suitable for a specific material.

Test principles and method choice

• Method A is direct calcination. The organic part is burned off and the residue is heated to constant mass.
• Method B adds sulfuric acid after burning. It is the common route to sulfated ash and is used when that form of ash is needed.
• Method C uses sulfuric acid before burning. EN ISO 3451-1:2026 says it is not applicable to silicones or fluorine-containing polymers and is used where volatile metal halides may be lost during burning.
• Method D is an automated instrument method based on the same general principle as method A.
• Method E is the thermogravimetric method. It is limited to direct calcination and cannot be used with sulfuric acid treatment.

Test conditions and apparatus

EN ISO 3451-1:2026 requires calcination at one of the specified temperature ranges, including 600 °C, 750 °C, 850 °C, 950 °C or 1 100 °C, with tighter tolerances for method E. For a lab, this means the furnace or thermobalance settings must be matched to the method and controlled well enough for repeatable results.

The test continues until constant mass is reached. For methods A, B, C or D, two weighings must differ by no more than 0.5 mg; for method E, the limit is 20 µg. The practical point is that the test does not end at a fixed time - it ends when the mass has stabilized.

The document also requires suitable apparatus such as crucibles, a muffle furnace or equivalent heat source, analytical balance, thermobalance for method E, pipettes for methods B and C, a desiccator, a weighing bottle and ventilation. It also requires regular verification of furnace operation, including temperature calibration and a check of ventilation efficiency.

Test portion, repeat tests and reporting

EN ISO 3451-1:2026 gives a table for selecting the test portion so that enough ash is obtained for measurement. If the ash content is unknown, a preliminary determination is used to choose the portion size. This matters because too little ash can make the result unreliable.

Unless the relevant material standard gives another rule, two determinations are carried out and repeated until two successive results differ by no more than 10 % of their mean. The result is reported as ash or sulfated ash as a percentage by mass, with the number of decimals depending on whether the value is above or below 1.

The test report must identify the standard, material, method used, calcination temperature, number and mass of test portions, individual results, mean value, any deviations, unusual observations and the test date.

What terms does EN ISO 3451-1:2026 define?

• Ash - the non-combustible residue left after the plastic has been calcined under the selected conditions.
• Sulfated ash - ash obtained after sulfuric acid treatment, used when the residue is converted to sulfates.
• Constant mass - the point at which two consecutive weighings meet the mass-difference limit in the method used.
• Thermobalance - an instrument that heats a sample while continuously measuring mass loss during the test.
• Repeatability limit - the difference below which two results under repeatability conditions may be expected to lie with 95 % probability.
• Reproducibility limit - the difference below which two results from different laboratories and operators may be expected to lie with 95 % probability.

Who uses EN ISO 3451-1:2026?

EN ISO 3451-1:2026 is used by plastics testing laboratories, quality-control teams, material suppliers and buyers who need to check ash content in a reproducible way. It is also used when a material specification calls for a particular ash test condition or when the ash result is part of product acceptance.

What changed in EN ISO 3451-1:2026 from the previous edition?

EN ISO 3451-1:2026 supersedes EN ISO 3451-1:2019 and technically revises ISO 3451-1:2019. The stated main changes are:

• an additional test temperature of 1 100 °C
• thermogravimetry, Method E, added as an alternative test method

Which standards are used with EN ISO 3451-1:2026?

Standard	What it contributes
ISO 472	Vocabulary for plastics terms used in the document
ISO 3451-2	Particular conditions for poly(alkylene terephthalate) materials
ISO 3451-3	Particular conditions for unplasticized cellulose acetate
ISO 3451-4	Particular conditions for polyamides
ISO 3451-5	Particular conditions for poly(vinyl chloride) plastics

What does the EN ISO 3451-1:2026 document contain?

EN ISO 3451-1:2026 contains a step-by-step test framework for ash determination in plastics, including method selection, apparatus requirements, reagent use for methods B and C, and detailed procedures for methods A through E. It also includes the sample-mass selection table, temperature and constant-mass conditions, and the instructions for rapid ashing where allowed.

The document provides precision data for methods A, B and C based on interlaboratory testing, and it links the result expression to a mass-percentage formula. It also specifies what must be recorded in the test report so that results can be compared between laboratories and traced back to the exact method used.

SLOVENSKI STANDARD
01-julij-2026
Polimerni materiali - Določanje pepela - 1. del: Splošne metode (ISO 3451-1:2026)
Plastics - Determination of ash - Part 1: General methods (ISO 3451-1:2026)
Kunststoffe - Bestimmung der Asche - Teil 1: Allgemeine Verfahren (ISO 3451-1:2026)
Plastiques - Détermination du taux de cendres - Partie 1: Méthodes générales (ISO 3451
-1:2026)
Ta slovenski standard je istoveten z: EN ISO 3451-1:2026
ICS:
83.080.01 Polimerni materiali na Plastics in general
splošno
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 3451-1
EUROPEAN STANDARD
NORME EUROPÉENNE
June 2026
EUROPÄISCHE NORM
ICS 83.080.01 Supersedes EN ISO 3451-1:2019
English Version
Plastics - Determination of ash - Part 1: General methods
(ISO 3451-1:2026)
Plastiques - Détermination du taux de cendres - Partie Kunststoffe - Bestimmung der Asche - Teil 1:
1: Méthodes générales (ISO 3451-1:2026) Allgemeine Verfahren (ISO 3451-1:2026)
This European Standard was approved by CEN on 29 May 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 3451-1:2026 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 3451-1:2026) 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 December 2026, and conflicting national standards
shall be withdrawn at the latest by December 2026.
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 3451-1:2019.
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 3451-1:2026 has been approved by CEN as EN ISO 3451-1:2026 without any
modification.
International
Standard
ISO 3451-1
Sixth edition
Plastics — Determination of ash —
2026-05
Part 1:
General methods
Plastiques — Détermination du taux de cendres —
Partie 1: Méthodes générales
Reference number
ISO 3451-1:2026(en) © ISO 2026

ISO 3451-1:2026(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 3451-1:2026(en)
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Reagents (for methods B and C only) . 2
6 Apparatus . 2
7 Procedure . 3
7.1 Test portion .3
7.1.1 General .3
7.1.2 Methods A, B, C or D .4
7.1.3 Method E .4
7.2 Test conditions .4
7.3 Method A — Direct calcination .5
7.4 Method B — Calcination following sulfuric acid treatment after burning .6
7.5 Method C — Calcination following sulfuric acid treatment before burning .6
7.6 Method D —Automated instrument method .7
7.7 Method E .7
8 Number of tests . 8
9 Expression of results . 8
10 Precision . 8
11 Test report . 9
Bibliography .10

iii
ISO 3451-1:2026(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 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).
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 5, Physical-
chemical properties, 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 sixth edition cancels and replaces the fifth edition (ISO 3451-1:2019), which has been technically
revised.
The main changes are as follows:
— an additional test temperature of 1 100 °C has been added;
— the thermogravimetry (Method E) has been added as alternative test method.
A list of all parts in the ISO 3451 series can be found on the ISO website.
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
International Standard ISO 3451-1:2026(en)
Plastics — Determination of ash —
Part 1:
General methods
WARNING — The use of this document can involve hazardous chemicals, materials, operations or
equipment. This document does not purport to address the safety problems associated with its use.
It is the responsibility of the user of this document to establish proper safety and health practices,
and to determine the application of regulatory limitations prior to use.
1 Scope
This document specifies general methods, with suitable test conditions, for the determination of the ash
of a range of plastics. The particular conditions chosen can be included in the specifications for the plastic
material in question.
Particular conditions applicable to poly(alkylene terephthalate) materials, unplasticized cellulose acetate,
polyamides and poly(vinyl chloride) plastics, including some specific filled, glass-fibre-reinforced and flame-
retarded materials, are specified in ISO 3451-2, ISO 3451-3, ISO 3451-4 and ISO 3451-5.
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 472, Plastics — Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 472 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/
4 Principle
It is possible to determine the ash of an organic material by five main methods (methods A, B, C, D and E).
a) Direct calcination, i.e. by burning the organic matter and heating the residue at high temperature until
constant mass is reached, which may be carried out by two different procedures:
— burning with, for example, a Bunsen burner and one or more calcining steps in a muffle furnace
(method A);
— burning and calcining as one single step in a muffle furnace (method A — rapid ashing), if it can be
demonstrated that the rapid ashing yields the same results as method A.

ISO 3451-1:2026(en)
b) Calcination after sulfation, which may be carried out by two different procedures:
— with sulfuric acid treatment after burning, i.e. by burning the organic matter, transforming the
inorganic residue into sulfates with concentrated sulfuric acid and heating the residue at high
temperature until constant mass is reached. This is the common method of obtaining “sulfated ash”
(method B);
— with sulfuric acid treatment before burning, i.e. by heating the organic matter together with
concentrated sulfuric acid up to temperatures where fuming and subsequent burning of the organic
matter occur, and finally heating the residue at high temperature until constant mass is reached
(method C). This procedure may be used if volatile metal halides are liable to evaporate during
burning of the organic matter. It is not applicable to silicones or fluorine-containing polymers.
c) Automated instrument method (method D);
d) Thermogravimetric method (method E).
In each case, the final step of the procedure is calcination at a pre-defined temperature (see 7.2).
NOTE The mass of the ash can vary with the temperature of calcination. For example, higher temperatures such
as 850 °C convert calcium carbonate and other carbonates to their oxides and thus give lower values for the ash.
5 Reagents (for methods B and C only)
During the analysis, only reagents of analytical grade and only distilled water or water of equivalent purity
shall be used.
5.1 Ammonium carbonate, anhydrous.
5.2 Ammonium nitrate, approximately 10 % (by mass) solution.
5.3 Sulfuric acid, concentrated 98 % (by volume), ρ = 1,84 g/cm .
WARNING — Sulfuric acid is highly corrosive. It shall be handled with suitable skin and eye protection
in a fume cupboard. It reacts exothermically with water.
5.4 Sulfuric acid, 50 % (by volume) solution.
WARNING — Sulfuric acid shall be handled with care. The sulfuric acid shall be prepared by slowly
adding the concentrated acid to water.
6 Apparatus
Some of the listed items may not be necessary for each method.
6.1 Crucible, made of silica, porcelain, ceramics, fibres, quartz, glass or platinum, inert to the material
tested and suitable for the temperatures used. The use of a crucible lid/watch-glass can be beneficial for
samples producing a fine particulate ash.
6.2 Gas burner, or other appropriate heat source.
6.3 Muffle furnace, powered by electric resistance heating or by microwave heating, capable of being
maintained at (600 ± 25) °C, (750 ± 50) °C, (850 ± 50) °C, (950 ± 50) °C or (1 100 ± 50) °C, as appropriate,
capable of measuring of temperature signals with an accuracy of ±2 % or better.
6.4 Analytical balance, for methods A, B, C or D, capable of determination of masses of test portions
according to Table 1 with an accuracy of 0,1 mg.

ISO 3451-1:2026(en)
6.5 Thermobalance, for method E, operated in air atmosphere and capable of heating up to and being
maintained at (600 ± 5) °C, (750 ± 5) °C, (850 ± 5) °C, (950 ± 5) °C or (1 100 ± 5) °C, as appropriate, and
continuously monitoring test temperatures with an accuracy of ±1 % or better of the absolute temperature
measured in K and masses of test portions according to Table 1 with an accuracy of ±20 µg or better.
6.6 For automated instruments and thermobalances, the following requirements apply:
— fully automatic analysis instrument with integrated drying oven or drying purge gas, muffle furnace or
other built-in heating
...