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

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

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.
GB/T 7762-2014
GB
NATIONAL STANDARD OF THE
PEOPLE REPUBLIC OF CHINA
ICS 83.060
G 40
Replacing GB/T 7762-2003
Rubber, vulcanized or thermoplastic ?€?
Resistance to ozone cracking ?€? Static Strain Test
??????????????????????€??????? ?€?????????????
(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 shall return to the test concentration within 30 min. The concentration of the ozone entering the chamber shall at no time exceed the concentration specified for the test.
5.4 Means of determining the ozone concentration
A means of sampling the ozonized air from the vicinity of the test pieces in the chamber and a means of estimating the ozone content are specified in ISO 1431-3. If required, the methods given in Annex B can also be a reference.
5.5 Means of adjusting the gas flow
A mechanism shall be provided that is capable of adjusting the average velocity of the flow of ozonized air in the test chamber to a value of not less than 8 mm/s and preferably to a value between 12 mm/s and 16 mm/s, calculated from the measured gas flow rate in the chamber divided by the effective cross-sectional area of the chamber normal to the gas flow. In tests intended to be comparable, the velocity shall not vary by more than ?? 10%. The gas flow rate is the volume throughout of ozonized air in...

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