introduction
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ISO 1431-1-222 “Ozone cracking resistance of plastics, vulcanized or thermoplastic rubber”

This document was prepared by Technical Committee ISO/TC 45, Rubber and Rubber Products, Subcommittee SC 2, Testing and Analysis.

The sixth edition cancels and replaces the technically revised fifth edition (ISO 1431-1:2012).

The main changes are as follows:

– Relative humidity is added to the range as a choice of test conditions (Article 1);

– The test chamber with humidity control has been specified in 5.2;

– Added high humidity test specifications in 5.5 and 9.3;

– Dumbbell type specimen is added in 7.4;

– The exposure period has been specified in 9.5;

– Two assessment methods (visual observation and image analysis) have been added to article 12;

– The determination of changes in physical or chemical properties has been added to 12.4.

A list of all the components in the ISO 1431 series can be found on the ISO website.

Any feedback or questions regarding this document should be directed to the user’s national standards body. A complete list of these institutions can be found at iso.org/members.html.

ISO 1431-1-222 “Ozone cracking resistance of plastics, vulcanized or thermoplastic rubber”

introduce
Ozone is usually found in small amounts in the atmosphere. However, even very small amounts of ozone can cause the sensitive rubber to crack under tensile strain, resulting in a loss of strength. Therefore, it is necessary to test the resistance of rubber to ozone.

Due to the uncertainty of natural exposure, ozone resistance testing of rubber is usually carried out in the laboratory using specially designed ozone cabinets.

Great care needs to be taken when attempting to correlate standard test results with performance in use, as the relative ozone resistance of different rubbers varies significantly depending on conditions, especially ozone concentration, temperature, and relative humidity. In addition, when tested on thin specimens deformed under tension, the impact of the size and the type and size of the deformation on the attack on the item in use can be very different.

An explanatory note on the properties of ozone lysis is contained in annex A.

Warning 1 Persons using this document should be familiar with normal laboratory practice. This document is not intended to address all security concerns, if any, associated with its use. It is the user’s responsibility to establish appropriate safety and health practices and to determine the applicability of any other restrictions.

Some of the procedures set out in this document may involve the use or production of substances, or the production of waste, which may pose a local environmental hazard. Appropriate documentation for safe handling and disposal after use should be consulted.

ISO 1431-1-222 “Ozone cracking resistance of plastics, vulcanized or thermoplastic rubber”

1 Range
This document specifies procedures for estimating the resistance of vulcanized or thermoplastic rubber to cracking when exposed to air containing a certain concentration of ozone under static or dynamic tensile strain, at a certain temperature, if required, and at a certain relative humidity, excluding the effect of direct light.

Visual observations and/or image analysis are used to assess crack formation and expansion. Changes in physical or chemical properties caused by exposure can also be identified.

Reference and alternative methods for determining ozone concentrations are described in ISO 1431-3.

2 Normative references
The following files are referenced in text in a manner that constitutes part or all of the requirements of this document. For dated references, only the cited version applies. For undated references, a new version of the reference (including any revisions) applies.

ISO 1382, rubber – Vocabulary

ISO 1431-3, vulcanized or thermoplastic rubber – Resistance to ozone cracking – Part 3: Reference and alternative methods for the determination of ozone concentrations in laboratory test chambers

ISO 18899:2013, Rubber – Guidance for calibration of test equipment

ISO 23529, Rubber – Physical test methods – General procedures for the preparation and conditioning of specimens

ISO 1431-1-222 “Ozone cracking resistance of plastics, vulcanized or thermoplastic rubber”

3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 1382 and the following articles apply.

ISO and IEC maintain terminology databases for standardization at the following addresses:

– ISO Online browsing platform: available at iso.org/obp

– IEC electronic encyclopedia: available at electropedia.org/

3.1 Threshold strain

At the highest tensile strain, at a given temperature, the rubber can be exposed to air containing a given concentration of ozone without ozone cracking on it after a given exposure time

Note 1: It is important to distinguish between threshold strain and limit threshold strain (3.2).

3.2 Limit threshold strain

The tensile strain, below which the time required for ozone cracks to develop will increase significantly and can become almost infinite

3.3 Dynamic Strain

The strain (usually tensile strain) changes sinusoidally with time at a selected repetition rate or frequency

Note 1: Maximum strain and repetition rate are used to describe dynamic strain conditions.

ISO 1431-1-222 “Ozone cracking resistance of plastics, vulcanized or thermoplastic rubber”

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