ISO 7681:2024

Natural rubber field latex — Determination of dry rubber content

This document specifies a method for the determination of the dry rubber content of natural rubber field latex. The method is not suitable for latices from natural sources other than Hevea brasiliensis, or for compounded latex, vulcanized latex or artificial dispersions of rubber.

Latex de plantation de caoutchouc naturel — Détermination de la teneur en caoutchouc sec

General Information

• Status: Published
• Publication Date: 21-Mar-2024
• 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 - Raw materials (including latex) for use in the rubber industry
• Current Stage: 6060 - International Standard published
• Start Date: 22-Mar-2024
• Due Date: 11-Aug-2024
• Completion Date: 22-Mar-2024

Overview

ISO 7681:2024 specifies a laboratory method for determining the dry rubber content (DRC) of natural rubber field latex from Hevea brasiliensis. The standard defines the principle, apparatus, reagents, two sheeting methods (hand and mechanical), calculation and reporting requirements. It is not applicable to latices from other natural sources, compounded or vulcanized latex, or artificial rubber dispersions.

Key topics and technical requirements

• Scope and limitation: Applies only to field latex (raw latex with or without preservative) from Hevea brasiliensis.
• Principle: Coagulate a weighed portion of latex, remove non‑rubber components, dry the coagulum and express DRC as a percentage by mass:
  • DRC (%) = (mass of dry rubber / mass of latex test portion) × 100
• Apparatus: ordinary lab equipment plus dish (glass/porcelain/aluminium), oven (70 °C ± 5 °C), desiccator, steam/water bath, analytical balance (1 mg readability), roller or laboratory mill, thickness gauge.
• Reagents: 2.0% acetic acid (for coagulation) and 95% ethanol (to clear serum when required); use analytical grade reagents and distilled water.
• Procedure options:
  • Method A (hand sheeting): press coagulum into ~2 mm sheet, wash thoroughly, drain, oven‑dry to translucence, cool and weigh; repeat drying until mass loss < 1 mg after 30 min.
  • Method B (mechanical sheeting): pass coagulum through a stainless‑steel mill with controlled roll speed and water spray to produce ~2 mm crepe, then wash/dry as above.
• Drying guidance: Standard drying at 70 °C ± 5 °C; reduce to ~55 °C if oxidative stickiness is suspected.
• Precision and reporting: Duplicate determinations shall not differ by more than 0.2 %. Annex A reports interlaboratory precision data from an ITP (six laboratories).

Practical applications and users

ISO 7681:2024 is used for:

• Quality control in natural rubber production and latex collection centers.
• Laboratory testing by rubber testing labs and research institutes.
• Buyers, traders and processors who require a verified DRC for pricing, specification compliance, and downstream processing.
• Agricultural extension services and field technologists monitoring latex quality.

Benefits include standardized DRC measurement, reproducible results across labs, and clear reporting requirements for traceability.

Related standards

• ISO 1382:2020 - Rubber - Vocabulary (definitions used)
• ISO 19983:2022 - Rubber - Determination of precision of test methods (used for precision evaluation)

Keywords: ISO 7681, dry rubber content, DRC, natural rubber field latex, Hevea brasiliensis, latex testing, coagulation, sheeting, laboratory method, precision, reproducibility.

Standards Content (Sample)

International
Standard
ISO 7681
First edition
Natural rubber field latex —
2024-03
Determination of dry rubber content
Latex de plantation de caoutchouc naturel — Détermination de
la teneur en caoutchouc sec
Reference number
© ISO 2024
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
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Phone: [phone]
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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 Reagent . 2
7 Procedure . 2
7.1 General .2
7.2 Method A: Sheeting by hand .2
7.3 Method B: Mechanical sheeting .3
8 Expression of results . 3
9 Precision . 3
10 Test report . 3
Annex A (informative) Precision data . 5
Bibliography . 7

iii
Foreword
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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.
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iv
International Standard ISO 7681:2024(en)
Natural rubber field latex — Determination of dry
rubber content
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 and to determine
applicable national regulatory conditions prior to use.
1 Scope
This document specifies a method for the determination of the dry rubber content of natural rubber field
latex. The method is not suitable for latices from natural sources other than Hevea brasiliensis, or for
compounded latex, vulcanized latex or artificial dispersions of rubber.
2 Normative references
There are no normative references in this document.
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
field latex
natural rubber latex with or without a preservative and prior to concentration or any other processing
Note 1 to entry: The preservative is added to maintain the original state of the latex as it came from the tree.
[SOURCE: ISO 1382:2020, 3.195]
3.2
dry rubb
...