ISO 19374:2026

• Abstract:

  This document establishes a designation system of recycled carbon fibres, which can be used as the basis for specification. This designation system is applicable to recycled carbon fibres used for polymer composites. The types of recycled carbon fibres are differentiated by a designation system based on appropriate levels of the designatory properties: tensile modulus of elasticity. tensile strength. NOTE One to five designatory property(s) that differentiate recycled carbon fibre types from each other is (are) assigned.

• Status: Published
• Publication Date: 14-Jun-2026
• ICS: 59.100.20 - Carbon materials
• Technical Committee: ISO/TC 61/SC 13 - Composites and reinforcement fibres
• Drafting Committee: ISO/TC 61/SC 13 - Composites and reinforcement fibres
• Current Stage: 6060 - International Standard published
• Start Date: 15-Jun-2026
• Due Date: 05-Dec-2026
• Completion Date: 15-Jun-2026

ISO 19374:2026 is an International Standard published by ISO for recycled carbon fibres used in polymer composites. It specifies a designation system that lets suppliers and users identify recycled carbon fibre types by source, form, sizing and key mechanical properties when writing specifications.

The standard is meant for specification, not for proving that two fibres will perform the same in service. For practical use, it gives a common code structure and lets additional application requirements be added in an optional block.

What does ISO 19374:2026 specify?

ISO 19374:2026 specifies a designation system for recycled carbon fibres, with recycled carbon fibres used for polymer composites as its intended field of application. Clause 4 sets the coding structure, and Clause 5 shows how a designation is built in practice.

Annex	What it covers
Annex A	Informative illustration of the source of carbon fibre recyclates

The document is organized into Scope, Normative references, Terms and definitions, Designation system, and Example of a designation. The core of the standard is Clause 4, which breaks the designation into data blocks for identification, product physical information, sizing information, mechanical properties and an optional block.

What are the key requirements of ISO 19374:2026?

Designation structure and syntax

ISO 19374:2026 uses a standardized pattern in Table 1. The designation begins with an identity block and the individual-item block starts with a hyphen; the data blocks are separated by commas. If a block is not used, the standard shows this by doubling the separator. In practice, this makes a designation machine-readable and reduces ambiguity in supplier documents and purchase specifications.

Data block 1 - identification

ISO 19374:2026 uses Data block 1 to identify the recycled carbon fibre by source and matrix type, using code letters in Table 2. The source categories include dry rCF, unprocessed PIR rCF, processed PIR rCF and processed PCR rCF, and the matrix type is identified as none, thermoplastic or thermoset. This is the first step in telling recyclate streams apart before considering performance.

Data block 2 - product physical information

ISO 19374:2026 uses Data block 2 for recovery process, form of the fibre product and fibre length, with the code system in Table 3. The fibre length is determined using ISO 6989. For users, this block shows whether the material is milled, chopped, randomly chopped, long fibre or continuous, which affects handling, compounding and the intended reinforcement form.

Data block 3 - sizing information

ISO 19374:2026 uses Data block 3 to state whether the fibre is sized, resized or unsized, and to indicate compatibility with thermoplastic or thermoset sizing agents, as shown in Table 4. If no specific information is given, the standard uses the no-indication code. This matters because sizing affects wetting, bonding and compatibility with the target polymer system.

Data block 4 - mechanical properties

ISO 19374:2026 uses Data block 4 for tensile modulus of elasticity and tensile strength, with ranges coded in Tables 5 and 6. Tensile modulus is determined in accordance with ISO 11566:1996, Method B, and tensile strength is determined using ISO 11566 and ISO 19350. The standard also notes that the modulus code is not mandatory for fibres shorter than 25 mm unless agreed, and the strength method in ISO 19350 can be applied to fibres as short as 3 mm by agreement.

Data block 5 - optional information

ISO 19374:2026 allows an optional Data block 5 for extra requirements or information agreed between user and supplier, including impurities or application-specific requirements. It can also point to official, traceable documents such as other standards, company standards or legal documents. This block is the place to add contract-specific details without changing the basic designation structure.

What terms does ISO 19374:2026 define?

• recycled carbon fibre (rCF) - carbon fibres recovered through a recycling process that retains usable properties.
• dry rCF (DrCF) - waste from pre-consumer carbon fibres and part of woven or non-woven fabric without uncured or cured matrix.
• post-industrial carbon fibre recyclate (PIR) - carbon fibres reclaimed after their intended use by industries.
• post-consumer carbon fibre recyclate (PCR) - carbon fibres reclaimed after their intended use by consumers.
• unprocessed PIR rCF (UPIrCF) - waste from thermoset or thermoplastic based prepreg.
• processed PIR rCF (PIrCF) - waste from thermoset or thermoplastic based PIR CFRP.
• processed PCR rCF (PCrCF) - waste from thermoset or thermoplastic based PCR CFRP.

Who uses ISO 19374:2026?

ISO 19374:2026 is used by recycled carbon fibre producers, composite material suppliers, and users who need to specify recyclate for polymer composites. It is also relevant to procurement teams, quality managers and test laboratories that have to classify materials, compare supplier declarations, write technical requirements and check whether a delivered product matches the agreed designation.

What changed in ISO 19374:2026 from the previous edition?

ISO 19374:2026 is the first edition of this standard.

Which standards are used with ISO 19374:2026?

• ISO 6989 - gives the reference method for determining fibre length by measurement of single fibres.
• ISO 11566:1996 - gives the reference method for determining tensile properties of single-filament specimens and is used here for tensile modulus of elasticity.
• ISO 19350 - gives the reference method for determining tensile strength distribution and interfacial shear strength of single filament embedded in matrix polymer, and is used here for tensile strength.

What does the ISO 19374:2026 document contain?

ISO 19374:2026 contains Table 1 for the designation pattern and Tables 2 to 6 for the code letters, code numbers and property ranges used in each data block. Clause 4 also gives the rules for separators, missing blocks, length determination and the use of reference test methods. Clause 5 provides example designations, including a four-block designation and a five-block designation that adds an extra specification reference. Annex A contains an informative figure showing the source of carbon fibre recyclates, which helps readers understand how the recyclate categories relate to the recycling stream.

International
Standard
ISO 19374
First edition
Recycled carbon fibres —
2026-06
Designation system for recycled
carbon fibres
Fibres de carbone recyclées — Système de désignation des fibres
de carbone recyclées
Reference number
© ISO 2026
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Designation system . 2
4.1 General .2
4.2 Data block 1 (Identification).3
4.3 Data block 2 (Product physical information) .4
4.4 Data block 3 (Sizing information) .4
4.5 Data block 4 (Mechanical properties of the product) .5
4.5.1 Tensile modulus of elasticity .5
4.5.2 Tensile strength .6
4.6 Data block 5 (Optional block) .6
5 Example of a designation . 7
5.1 Designation with four data blocks .7
5.2 Designation with five data blocks .7
Annex A (informative) Illustration of the source of carbon fibre recyclates . 8

iii
Foreword
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iv
Introduction
Carbon fibres are applied for the reinforcement of polymers or other materials. In particular, the recycled
carbon fibres are being highly durable and have limited degradation through recycling, their reuse for
adaption to circular economy is of much value. This designation system of recycled carbon fibres is necessary
to clearly specify the identification of essential characteristics of recycled carbon fibres.

v
International Standard ISO 19374:2026(en)
Recycled carbon fibres — Designation system for recycled
carbon fibres
1 Scope
1.1 This document establishes a designation system of recycled carbon fibres, which can be used as the
basis for specification.
1.2 This designation system is applicable to recycled carbon fibres used for polymer composites.
1.3 The types of recycled carbon fibres are differentiated by a designation system based on appropriate
levels of the designatory properties:
a) tensile modulus of elasticity.
b) tensile strength.
NOTE One to five designatory property(s) that differentiate recycled carbon fibre types from each other is (are)
assigned.
1.4 It is not intended to imply that recycled carbon fibres having the same designation will give the same
performance. This document does not provide engineering data or data on processing conditions that can be
required to specify materials for a particular and/or method of processing.
1.5 In order to specify recycled carbon fibres for a particular application, additional requirements are
given in optional data block 5 (see 4.6).
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 6989, Textile fibres — Determination of length and length distribution of staple fibres (by measurement of
single fibres)
ISO 11566:1996, Carbon fibre — Determination of the tensile properties of single-filament specimens
ISO 19350, Recycled carbon fibre — Determination of tensile strength distribution and interfacial shear strength
of single filament embedded in matrix polymer
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
recycled carbon fibre
rCF
carbon fibres recovered through a recycling process that retains usable properties
3.2
dry rCF
DrCF
waste from pre-consumer carbon fibres and from a part of woven and non-woven fabric (without uncured
or cured matrix, only fibres)
Note 1 to entry: See Figure A.1
3.3
post-industrial carbon fibre recyclate
PIR
carbon fibres reclaimed after their intended use by industries
No
...