ISO 9782:2026

• Abstract:

  This document specifies a method for the determination of the apparent volatile-matter content in pre-impregnated yarns, tapes, mats (SMC) and fabrics. The method is applicable to all unidirectional and multidirectional fibre-reinforced prepregs and all thermosetting-resin matrices, unless otherwise specified in product specifications. The method does not apply to unimpregnated reinforcement fibres. NOTE For products with a polyester-resin matrix (UP), the result will be lower than the real value.

• Status: Published
• Publication Date: 06-Jul-2026
• ICS: 83.120 - Reinforced plastics
• Technical Committee: ISO/TC 61/SC 13 - Composites and reinforcement fibres
• Drafting Committee: ISO/TC 61/SC 13/WG 2 - Laminates and moulding compounds
• Current Stage: 6060 - International Standard published
• Start Date: 07-Jul-2026
• Due Date: 21-Nov-2027
• Completion Date: 07-Jul-2026

• Revises: ISO 9782:1993 - Plastics — Reinforced moulding compounds and prepregs — Determination of apparent volatile-matter content
• Effective Date: 07-Jan-2025

ISO 9782:2026 is an International Standard published by ISO for determining the apparent volatile-matter content of reinforced moulding compounds and prepregs. It specifies a gravimetric heating method for pre-impregnated yarns, tapes, mats (SMC) and fabrics made with thermosetting-resin matrices, so laboratories and material users can measure the volatile content in a consistent way.

What does ISO 9782:2026 specify?

ISO 9782:2026 specifies a method for measuring apparent volatile-matter content in pre-impregnated reinforcement products. It applies to unidirectional and multidirectional fibre-reinforced prepregs and to thermosetting-resin matrices, unless a product specification sets a different requirement.

The method does not apply to unimpregnated reinforcement fibres. The scope also notes that for products with a polyester-resin matrix (UP), the measured result will be lower than the real value, which matters when comparing results with the actual volatile content in service or production.

Annex	What it covers
Annex A	Precision data from an interlaboratory test

The document is organized into scope, normative references, terms and definitions, principle, apparatus, sampling and test specimens, conditioning and test atmosphere, procedure, calculation and expression of results, precision, and test report.

What are the key requirements of ISO 9782:2026?

ISO 9782:2026 uses a loss-on-heating method: the apparent volatile-matter content is the percentage of mass lost when a specimen is heated in an air-ventilated oven for a specified time at a specified temperature. In practice, the result depends on controlled weighing, heating, cooling and calculation steps.

Measuring principle and correction for aramid fibres

Clause 4 states that the test compares the initial mass with the mass after heating. For aramid fibres, absorbed water is removed together with volatile matter at the test temperature, so the result has to be corrected by subtracting the water content. This matters because otherwise the test can overstate the volatile fraction.

Apparatus and control of the test

Clause 5 requires a cutting device, a balance accurate to 0,1 mg, an air-ventilated oven that can hold the chosen temperature within ±5 °C, a desiccator, suitable specimen holders, and a timer reading 60 min ± 1 min. These controls matter because small mass changes are being measured, so balance sensitivity, oven stability and timed heating all affect the result.

Sampling and test specimen preparation

Clause 6 requires sampling in accordance with the relevant material specification. It also requires at least three test specimens per sample, taken across the full width of the laboratory sample, or staggered along the length when the sheet is less than 30 cm wide, and at least 5 cm from the edges. This helps the test represent the material rather than an edge effect or a local variation.

Conditioning and test atmosphere

Clause 7 requires conditioning enough material to prepare the required specimens, in the selected standard atmosphere, without removing the protective sheets, and in a waterproof bag if needed. The test atmosphere shall be one of the standard atmospheres in ISO 291. This matters because moisture and temperature before testing can change the mass loss.

Procedure, heating conditions and calculation

Clause 8 requires quick weighing after cutting, weighing of any protective sheets, heating on a pre-weighed holder or support, and cooling in a desiccator before the final weighing. The specimen should be placed so that the maximum surface area is exposed to the circulating heat.

When no temperature or time is given in the material specification, Table 1 gives recommended oven temperatures and heating times by resin type. Clause 9 then calculates volatile-matter content from the mass change and reports the arithmetic mean of the three determinations. In practice, this gives one result for batch control or specification checking.

Precision and reporting

Clause 10 points to Annex A for interlaboratory precision data, including repeatability and reproducibility. Clause 11 sets the test report items, including the standard reference, full material identification, mean result, test conditions, date and any deviation from the method. That helps users compare results from different laboratories.

What terms does ISO 9782:2026 define?

• Apparent volatile-matter content - the percentage of matter lost on heating relative to the initial mass.
• Prepregs - pre-impregnated yarns, tapes, mats and fabrics that are tested by this method.
• SMC - a mat form named in the scope and covered by the method.
• Thermosetting-resin matrix - the resin system to which the method applies, unless a product specification says otherwise.
• UP - polyester-resin matrix; the scope notes that the measured result will be lower than the real value for these products.
• Repeatability - the closeness of test results obtained under repeatability conditions, as used in Annex A.
• Reproducibility - the closeness of test results obtained under reproducibility conditions, as used in Annex A.

Who uses ISO 9782:2026?

ISO 9782:2026 is used by laboratories, composites manufacturers, quality control teams, and suppliers of reinforced moulding compounds and prepregs. Buyers and specification writers use it when they need a clear test method for material acceptance, and technical staff use it to compare batches, verify product specifications, and record test conditions in reports.

It is relevant in plastics and composites work where pre-impregnated fibre products are made, tested, or purchased.

What changed in ISO 9782:2026 from the previous edition?

ISO 9782:2026 cancels and replaces ISO 9782:1993 and has been technically revised. The stated changes are:

• balance weighing accuracy raised from ±1 mg to ±0,1 mg
• a timer added to the apparatus clause
• symbol V added in the calculation formula
• number of test specimens changed from three to at least three
• an instruction added to place specimens so that the maximum surface area is exposed to circulating heat
• a precision statement added in Annex A

Which standards are used with ISO 9782:2026?

ISO 9782:2026 uses ISO 291, Plastics - Standard atmospheres for conditioning and testing, as its normative reference. ISO 291 supplies the standard atmospheres used for conditioning and for the test atmosphere, so it controls the environmental conditions around the weighing and heating procedure.

What does the ISO 9782:2026 document contain?

ISO 9782:2026 contains a full test method rather than a short requirement list. It includes the principle of the measurement, the apparatus needed, specimen sampling and preparation, conditioning instructions, the heating and weighing procedure, and the calculation used to express apparent volatile-matter content.

It also includes Table 1 with recommended oven temperatures and heating times when the material specification does not state them. Annex A provides interlaboratory precision data, including repeatability and reproducibility results for two prepreg materials and two specimen placement methods.

International
Standard
ISO 9782
Second edition
Plastics — Reinforced moulding
2026-07
compounds and prepregs —
Determination of apparent volatile-
matter content
Plastiques renforcés — Compositions pour moulage et
préimprégnés — Détermination de la teneur apparente en
matières volatiles
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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Published in Switzerland
ii
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Apparatus . 1
6 Sampling and test specimens . 2
6.1 Sampling .2
6.2 Shape and dimensions .2
6.3 Preparation and number of test specimens.2
7 Sample conditioning and test atmosphere. 2
7.1 Sample conditioning .2
7.2 Test atmosphere .2
8 Procedure . 2
9 Calculation and expression of results . 3
10 Precision . 3
11 Test report . 3
Annex A (informative) Precision data obtained from an interlaboratory test . 4

iii
Foreword
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This document was prepared by Technical Committee ISO/TC 61, Plastics, Subcommittee SC 13, Composites
and reinforcement fibres.
This second edition cancels and replaces the first edition (ISO 9782:1993), which has been technically
revised.
The main changes are as follows:
— the requirement for the weighing accuracy of balances has been raised from ±1 mg to ±0,1 mg;
— a timer has been added in the apparatus clause;
— the symbol V for volatile-matter content in the calculation formula has been supplemented;
c
— the number of test specimens has been changed from "three" to "at least three";
— the following instruction has been added to 8.4 “The specimens should be placed so that the maximum
surface area is exposed to the circulating heat.”;
— a precision statement has been added in Annex A.
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 9782:2026(en)
Plastics — Reinforced moulding compounds and prepregs —
Determination of apparent volatile-matter content
1 Scope
This document specifies a method for the determination of the apparent volatile-matter content in pre-
impregnated yarns, tapes, mats (SMC) and fabrics.
The method is applicable to all unidirectional and multidirectional fibre-reinforced prepregs and all
thermosetting-resin matrices, unless otherwise specified in product specifications.
The method does not apply to unimpregnated reinforceme
...