ISO 17278:2020

Rubber, raw natural - Determination of the gel content of technically specified rubber (TSR)

This document specifies a method for the determination of gel content for technically specified rubbers (TSR).

Caoutchouc naturel brut — Détermination de la teneur en gel des caoutchoucs spécifiés techniquement (TSR)

General Information

• Status: Published
• Publication Date: 29-Apr-2020
• ICS: 83.040.10 - Latex and raw rubber
• Technical Committee: ISO/TC 45/SC 3 - Raw materials (including latex) for use in the rubber industry
• Drafting Committee: ISO/TC 45/SC 3/WG 4 - Natural rubber
• Current Stage: 9093 - International Standard confirmed
• Start Date: 11-Jun-2025
• Completion Date: 13-Dec-2025

Relations

• Revises: ISO 17278:2013 - Rubber, raw natural - Determination of the gel content of technically specified rubber (TSR)
• Effective Date: 23-Apr-2020

Overview

ISO 17278:2020 specifies a laboratory test method for measuring the gel content of technically specified rubber (TSR) - raw natural rubber processed from Hevea brasiliensis. The method determines the insoluble (gel) fraction by dissolving TSR in toluene, separating the insoluble material by centrifugation, drying and weighing the residue. Results are reported as a percentage gel content (rounded to one decimal place).

Key topics and requirements

• Principle: dissolve a defined mass of TSR in toluene, allow extraction, centrifuge to separate insoluble gel, remove solvent, dry precipitate and calculate gel content as a percentage of the original sample mass.
• Reagents: analytical-grade toluene (primary solvent) and acetone (for rinsing precipitate).
• Apparatus & accuracy:
  • Laboratory centrifuge: 14 000 r/min (recommended) or minimum 8 000 r/min with extended time.
  • Screw-cap centrifuge tubes (≥30 cm3) able to withstand >110 °C.
  • Balance accurate to ±0.1 mg and weighing containers to ±1 mg.
  • Oven capable of 110 °C ±10 °C and a desiccator.
• Test conditions & procedure:
  • Sample ratio: typically 0.1 g TSR per 30 cm3 toluene.
  • Extraction: stand 16–20 h at (25 ± 2) °C in the dark.
  • Centrifugation: 14 000 r/min for 2 h (or 8 000 r/min for 6 h).
  • Drying: precipitate dried at 110 °C for 1 h; repeat weighings until mass change <0.2 mg.
• Calculation: Gel content G (%) = (m2 − m1) / m0 × 100, where m0 = original test piece mass, m1 = empty container mass, m2 = container + dry precipitate mass.
• Precision: Annex A reports interlaboratory repeatability and reproducibility values across low, medium and high gel levels; precision depends on gel content level.
• Safety & lab practice: warns about solvent handling and standard laboratory safety; conditioning per ISO 23529.

Applications and users

ISO 17278:2020 is intended for:

• Quality control laboratories in natural rubber production and processing.
• Third‑party testing services validating TSR batches for suppliers and purchasers.
• R&D and product development teams assessing rubber processing effects (mixing, storage, coagulation) on gel formation.
• Procurement/specification engineers who require documented gel-content results for acceptance criteria.

Practical uses include batch acceptance testing, supplier quality verification, and comparative studies of processing methods that influence gel formation in TSR.

Related standards

• ISO 2000:2014 - Guidelines for specification of technically specified rubber (TSR).
• ISO 23529 - Conditioning and general procedures for rubber test pieces.
• Precision methodology reference: ISO/TR 9272 (withdrawn; now superseded by ISO 19983) is cited for precision evaluation.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 17278
Second edition
2020-04
Rubber, raw natural — Determination
of the gel content of technically
specified rubber (TSR)
Caoutchouc naturel brut — Détermination de la teneur en gel des
caoutchoucs spécifiés techniquement (TSR)
Reference number
©
ISO 2020
© ISO 2020
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
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Published in Switzerland
ii © ISO 2020 – All rights reserved

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Reagent . 1
6 Apparatus . 2
7 Conditions. 2
8 Procedure. 2
8.1 Number of test samples . 2
8.2 Procedure . 2
9 Expression of the result. 3
10 Precision . 4
11 Test report . 4
Annex A (informative) Precision . 5
Bibliography . 7
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
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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).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
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www .iso .org/ iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 45, Rubber and rubber products,
Subcommittee SC 3, Raw materials (including latex) for use in the rubber industry.
This second edition cancels and replaces the first edition (ISO 17278:2013), which has been technically
revised.
The main changes compared to the previous edition are as follows:
— to solve the ambiguity with the scope, the term “LoV-TSR sample” in Clause 4 has been replaced by
the term “TSR sample”;
— in 8.1, the words “two samples” have been replaced by “two test samples”;
— in 5.2, acetone has been added.
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 © ISO 2020 – All rights reserved

INTERNATIONAL STANDARD ISO 17278:2020(E)
Rubber, raw natural — Determination of the gel content of
technically specified rubber (TSR)
WARNING — Persons using this document should be familiar with normal laboratory practice.
This document does not purport to address all of the safety problems, if any, associated with its
use. It is the responsibility of the user to establish appropriate safety and health practices.
1 Scope
This document specifies a method for the determination of gel content for technically specified
rubbers (TSR).
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 2000:2014, Rubber, raw natural — Guidelines for the specification of technically specified rubber (TSR)
ISO 23529, Rubber — General procedures for preparing and conditioning test pieces for physical test methods
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
technically specified rubber
TSR
natural rubber obtained from the latex of Hevea brasiliensis (typically processed into block rubber), and
having properties complying with the criteria for the grade concerned
4 Principle
A TSR sample is d
...