ISO 14322:2018

Plastics - Epoxy resins - Determination of degree of crosslinking of crosslinked epoxy resins by differential scanning calorimetry (DSC)

This document specifies a method whereby the heat of reaction generated during epoxy resin crosslinking is measured by differential scanning calorimetry (DSC). The degree of crosslinking is determined based on this result. This method is applicable to epoxy resin systems with a moderate or slow crosslinking-reaction speed. It might not be applicable to systems with a fast crosslinking-reaction speed at ambient temperature.

Plastiques — Résines époxydes — Détermination du degré de réticulation des résines époxydes réticulées par analyse calorimétrique différentielle (DSC)

General Information

• Status: Published
• Publication Date: 18-Jul-2018
• ICS: 83.080.10 - Thermosetting materials
• Technical Committee: ISO/TC 61/SC 12 - Thermosetting materials
• Drafting Committee: ISO/TC 61/SC 12/WG 5 - Unsaturated polyesters, epoxy resins and other resins
• Current Stage: 9093 - International Standard confirmed
• Start Date: 18-Dec-2023
• Completion Date: 13-Dec-2025

Relations

• Consolidated By: ISO 9073-1:2023 - Nonwovens - Test methods - Part 1: Determination of mass per unit area
• Effective Date: 06-Jun-2022
• Revises: ISO 14322:2012 - Plastics - Epoxy resins - Determination of degree of crosslinking of crosslinked epoxy resins by differential scanning calorimetry
• Effective Date: 30-Sep-2017

Overview

ISO 14322:2018 - Plastics - Epoxy resins - Determination of degree of crosslinking of crosslinked epoxy resins by differential scanning calorimetry (DSC) specifies a DSC-based method to quantify the degree of crosslinking in epoxy resin systems. The method measures the heat of reaction remaining in a partly crosslinked sample and compares it to the total heat of reaction of the uncured system to calculate crosslink percentage. It is intended for epoxy systems with moderate or slow crosslinking speeds and may not be suitable for systems that cure very rapidly at ambient temperature.

Key Topics and Requirements

• Principle: Determine total reaction heat (uncrosslinked) and residual reaction heat (partly crosslinked) by DSC; degree of crosslinking C = (1 − Hs / Hr) × 100, where Hr = total heat of reaction and Hs = heat remaining in the sample.
• Sample and measurement:
  • Typical sample mass: 10–20 mg, weighed to 0.01 mg precision.
  • DSC apparatus requirements: heating rate up to 10 °C/min, temperature measurement within ±0.1 °C, heat-flux precision ±1%, operating range at least 20 °C–300 °C.
  • Gas flow around sample with flow meter able to measure 10–50 ml/min.
  • Pans must be thermally conductive and chemically compatible.
• Calibration and controls: Calibrate per ISO 11357‑1; indium is commonly used.
• Preliminary test: Verify applicability by measuring total heat of reaction on two uncured samples taken consecutively - agreement must be within ±10% relative to the average.
• Procedure: Conduct DSC for uncured and partly cured samples under identical time‑temperature programs; average duplicates for final values.
• Precision & reporting: Clause on interlaboratory precision and required test-report contents (sample ID, DSC program, measured heats, calculated degree of crosslinking).

Applications

• R&D and formulation development: Optimize curing schedules and catalyst or hardener selection.
• Production and quality control: Verify batch-to-batch cure state and ensure target crosslink levels in adhesives, coatings, composites and encapsulants.
• Failure analysis and process validation: Confirm incomplete cures or overcure in thermoset systems used in electronics, automotive and aerospace components.
• Users: Polymer scientists, materials engineers, QC laboratories, DSC analysts and thermoset manufacturers.

Related Standards

• ISO 11357‑1 - Differential scanning calorimetry (DSC) - General principles (calibration and measurement basics).
• ISO 11409 - Heats and temperatures of reaction by DSC (methods for calculating reaction heats).

Keywords: ISO 14322:2018, epoxy resins, DSC, differential scanning calorimetry, degree of crosslinking, heat of reaction, epoxy cure testing.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 14322
Second edition
2018-07
Plastics — Epoxy resins —
Determination of degree of
crosslinking of crosslinked epoxy
resins by differential scanning
calorimetry (DSC)
Plastiques — Résines époxydes — Détermination du degré
de réticulation des résines époxydes réticulées par analyse
calorimétrique différentielle (DSC)
Reference number
©
ISO 2018
© ISO 2018
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 © ISO 2018 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Materials . 3
6 Apparatus . 3
7 Procedure. 3
7.1 Calibration . 3
7.2 Preliminary test . 4
7.2.1 General. 4
7.2.2 Procedure for preliminary test . 4
7.3 DSC measurement on the crosslinked resin under investigation . 4
8 Expression of results . 5
9 Precision . 5
9.1 General . 5
9.2 Materials and crosslinking conditions . 5
9.3 Precision of the method . 5
10 Test report . 6
Annex A (informative) Example of a procedure used for the preliminary test, with typical
operating conditions . 7
Bibliography . 8
Foreword
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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).
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URL: www .iso .org/iso/foreword .html.
This document was prepared by Technical Committee ISO/TC 61, Plastics, Subcommittee SC 12,
Thermosetting materials.
This second edition cancels and replaces the first edition (ISO 14322:2012), of which it constitutes a
minor revision.
The changes compared to the previous edition are as follows:
— the title has been updated (DSC has been added at the end);
— Clause 2 has been updated;
— the subclauses under 7.2 have been renumbered;
— editorial changes have been applied.
Any feedback or questions on this document should be directed to the user’s national standards body. A
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iv © ISO 2018 – All rights reserved

Introduction
It is possible to determine the degree of crosslinking of a crosslinked epoxy resin by observing changes
in its mechanical, electrical or thermal properties.
However, such an approach is inadequate in cases in which the test sample is to be evaluated as is or
is to be examined under various crosslinking conditions. This document provides a method whereby
the degree of crosslinking is determined without the need for complicated procedures for preparing,
conditioning or configuring the test sample. The degree of crosslinking is determined by comparing the
heat of the crosslinking reaction for the test sample with that of a reference sample, using a differential
scanning calorimeter.
The advantages of this method are that sample preparation is simple and measurements can be made
with very small amounts of sample. For these reasons, this document is useful for investigations of,
and in establishing conditions for, crosslinking reactions. It can also be used for production and quality
control.
Finally, since epoxy resin systems are highly diverse, the applicability of this document to each resin
system needs be established. A technique to test the applicability to an epoxy resin system is included
in this document.
INTERNATIONAL STANDARD ISO 14322:2018(E)
Plastics — Epoxy resins — Determination of degree of
crosslinking of crosslinked epoxy resins by differential
scanning calorimetry (DSC)
SAFETY STATEMENT — Persons using this document should be familiar with normal laboratory
practice, if applicable. This document does not purport to address all of the safety concerns, if
any, associated with its use. It is the responsibility of the user to establish appropriate safety
and health practices and to determine the applicability of any other restrictions.
1 Scope
This document specifies a method whereby the heat of reaction generated during epoxy resin
crosslinking is measured by differential scanning calorimetry (DSC). The degree of crosslinking is
determined based on this result.
This method is applicable to epoxy resin systems with a moderate or slow crosslinking-reac
...