ISO 16947:2026

International
Standard
ISO 16947
First edition
Natural rubber latex concentrate —
2026-02
Determination of zinc oxide
stability time (ZST)
Concentré de latex de caoutchouc naturel — Détermination du
temps de stabilité de l'oxyde de zinc (ZST)
Reference number
© ISO 2026
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ii
Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Reagents . 2
6 Apparatus . 2
7 Sampling . 2
8 Procedure . 2
9 Expression of results . 3
10 Precision . 3
11 Test report . 4
Annex A (informative) Precision . 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 16947:2026(en)
Natural rubber latex concentrate — Determination of zinc
oxide stability time (ZST)
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 determine the applicability of
regulatory limitations prior to use.
1 Scope
This document specifies a method for determining the zinc oxide stability time (ZST) of natural rubber latex
concentrate.
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 35, Natural rubber latex concentrate — Determination of mechanical stability
ISO 123, Rubber latex — Sampling
ISO 124, Latex, rubber — Determination of total solids content
ISO 976, Rubber and plastics — Polymer dispersions and rubber latices — Determination of pH
ISO 3310-1, Test sieves — Technical requirements and testing — Part 1: Test sieves of metal wire cloth
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
zinc oxide stability time
ZST
time required to initiate visible flocculation after the addition of zinc oxide when the latex is stirred at high
speed
Note 1 to entry: The zinc oxide stability time is expressed in seconds.
4 Principle
A test portion, under specified alkalinity, dilution and temperature is stirred at high speed after the addition
of zinc oxide until visible flocculation is observed. The time required to initiate visible flocculation is
recorded, this
...