GB/T 7762-2014 English PDF (GBT7762-2014)

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GB/T 7762-2014: Rubber, vulcanized or thermoplastic -- Resistance to ozone cracking -- Static strain test
GB/T 7762-2014
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 83.060
G 40
Replacing GB/T 7762-2003
Rubber, vulcanized or thermoplastic –
Resistance to ozone cracking – Static Strain Test
硫化橡胶或热塑性橡胶 耐臭氧龟裂
(ISO 1431-1.2004, Rubber, vulcanized or thermoplastic -Resistance to ozone
cracking – Part 1. Static and dynamic strain testing, NEQ)
ISSUED ON. DECEMBER 22, 2014
IMPLEMENTED ON. JUNE 1, 2015
Issued by. General Administration of Quality Supervision, Inspection and
Quarantine of the People's Republic of China;
Standardization Administration of the People's Republic of
China.
Table of Contents
Foreword ... 3 
1 Scope ... 5 
2 Normative references ... 5 
3 Terms and definitions ... 6 
4 Principle ... 6 
5 Apparatus ... 6 
6 Test pieces ... 10 
7 Conditioning ... 11 
8 Test conditions ... 12 
9 Static strain testing ... 13 
10 Expression of results ... 14 
11 Test report... 16 
Annex A (Informative) Ozone cracking – Explanatory notes ... 18 
Annex B (Informative) Method for the determination of ozone concentration –
Iodometric titration method ... 20 
Foreword
This Standard was drafted in accordance with the rules given in GB/T 1.1-2009.
This Standard replaces GB/T 7762-2003, Rubber, vulcanized or thermoplastic –
Resistance to ozone cracking – Static Strain Test; compared with GB/T 7762-2003, the
main technical differences of it are as follows.
-- it deletes the specification that oxygen is recommended when ozone is made with
silent-discharge tube (see 5.2 of Edition 2003);
-- it uses GB/T 2941 to replace GB/T 9865.1 (see 6.1; 6.1 of Edition 2003);
-- it modifies the dimensions of the narrow test piece and adds the alternative dumb-
bell test pieces in accordance with GB/T 528 (see 6.3; 6.3 of Edition 2003);
-- for products intended for use in damp climates, it modifies the requirements for
its relative humidity during the test, from the original “the test shall be carried out
at a relative humidity in the range 80% to 90%” into “the test shall be carried out
at a relative humidity in the range 80% to 90%, if this is practicable” (see 8.3; 8.3
of Edition 2003).
-- it adds an optional elongation (25 ± 2)% (see 8.4); and
-- it adds an optional method for observation and evaluation of cracking. in
accordance with relevant provisions of GB/T 11206-2009 (see 10.1).
This Standard was redrafted by reference to ISO1431-1.2004, Rubber, vulcanized or
thermoplastic – Resistance to ozone cracking – Part 1. Static and dynamic strain
testing. It is not equivalent to ISO 1431-1.2004.
This Standard was proposed by China Petroleum and Chemical Industry Federation.
This Standard shall be under the jurisdiction of the Subcommittee of General Test
Methods of the National Standardization Technical Committee on Rubber and Rubber
Products (SAC/TC 35/SC 2).
The drafting organizations of this Standard. Guangzhou Synthetic Materials Research
Institute Co., Ltd., Guangzhou Huanan Rubber Tyre Co., Ltd., Aeolus Tyre Co., Ltd.,
Jiangsu Mingzhu Testing Machinery Co., Ltd., Guizhou Tyre Co., Ltd., Beijing
Research and Design Institute of Rubber Industry, Zhongce Rubber Group Co., Ltd.
and Guangzhou Industrial Rubber Products Research Institute Co., Ltd.
The main drafters of this Standard. Xie Yufang, Yi Jun, Liang Yaping, Luo Jiliang, Ren
Shaowen, Liu Yuwan, Zhu Ming, Feng Ping, Xie Junfang, Li Jing, Xiang Chan and
Zhao Yanfen.
This Standard shall be interpreted by the Secretariat of National Standardization
Technical Committee on Fasteners.
The previous editions replaced by this Standard are as follows.
-- GB/T 7762-1987 and GB/T 7762-2003.
Rubber, vulcanized or thermoplastic –
Resistance to ozone cracking – Static Strain Test
WARNING 1 – Persons using this Standard should be familiar with normal
laboratory practice. This Standard 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 ensure compliance with
any national regulatory conditions.
WARNING 2 – Attention is drawn to the highly toxic nature of ozone. Efforts
should be made to minimize the exposure of workers at all times. It is usually
recommended that 0.1 part of ozone per million parts of air of the surrounding
atmosphere by volume be regarded as an absolute maximum concentration
whilst the maximum average concentration should be appreciably lower. Unless
a totally enclosed system is being used, an exhaust vent to remove ozone-laden
air is advised.
1 Scope
This Standard specifies procedures intended for use in estimating the resistance of
vulcanized or thermoplastic rubbers to cracking when exposed, under static tensile
strain, to air containing a definite concentration of ozone and at a definite temperature
in circumstances that exclude the effects of direct light.
This Standard applies to rubber, vulcanized or thermoplastic.
NOTE Great caution is necessary in attempting to relate standard test results to service
performance since the relative ozone resistance of different rubbers can vary markedly
depending on the conditions, especially ozone concentration and temperature. In addition, tests
are carried out on thin test pieces deformed in tension and the significance of attach for articles
in service can be quite different owing to the effects of size and of type and magnitude of the
deformation. Explanatory notes on the natural ageing under ozone cracking are given in Annex
A.
2 Normative references
The following referenced documents are indispensable for the application of this
document. For dated references, only the edition dated applies to this document. For
undated references, the latest edition of the referenced document (including any
amendments) applies to this Standard.
GB/T 528-2009, Rubber, vulcanized or thermoplastic – Determination of tensile
stress-strain properties (ISO 37.2005, IDT)
b) silent-discharge tube.
Air used for generation of ozone or for dilution shall first be purified by passing it over
activated charcoal and shall be free from any contaminants likely to affect the ozone
concentration, the estimation of the ozone concentration or the cracking of the test
pieces.
NOTE Theoretically, nitrogen oxides can be generated when air is used to make ozone with
silent-discharge tube, which interferes the test, but this interference will not occur under low
ozone concentration as specified by standard.
The temperature of the source shall be kept constant to within ± 2°C.
The ozonized air shall be fed from the source into the chamber via a heat exchanger
to adjust its temperature to that required for the test and shall also be brought to the
specified relative humidity.
5.3 Means of adjusting the ozone concentration
When an ultra-violet lamp is used, the ozone concentration can be controlled by
adjusting either the voltage applied to the tube or the input-gas flow rate, or by shielding
part of the tube from the UV light. When a silent-discharge tube is used, the ozone
concentration can be controlled by adjusting the voltage applied to the generator, the
dimensions of electrodes, or the oxygen or diluent-air flow rate. The adjustments shall
be such that they will maintain the concentration within the tolerances given in 8.1. In
addition, after each occasion that the test chamber opened for insertion or inspection
of test pieces, the ozone concentration ...