This standard specifies test method and evaluation method for surface cracking of rubber specimens when deteriorating under static strain.
It is applicable to the aging test of rubber under static strain or bending state in atmospheric environment or zone-containing medium.
It is not applicable to test of electrical insulation or other rubber parts where high concentrations of ozone prevail due to electrical discharge, nor to test of hard rubber.
2 Normative references
The following documents contain provisions which, through reference in this text, constitute provisions of this standard. For dated references, subsequent amendments to (excluding corrections), or revisions of, any of these publications do not apply. However, parties to agreements based on this standard are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. For undated references, the latest editions apply.
GB/T 528 Rubber, vulcanized or thermoplastic - Determination of tensile stress-strain properties (GB/T 528-1998, eqv ISO 37: 1994)
GB/T 7762 Rubber, vulcanized or thermoplastic - Resistance to ozone cracking - Static strain test (GB/T 7762-2003, ISO 1431-1: 1989, MOD)
ASTM D 4575 Standard test methods for rubber deterioration - Reference and alternative method(s) for determining ozone level in laboratory test chambers
3 Test methods
3.1 According to the actual use state of rubber or rubber products, the following methods may be selected for the test:
a) strain method of rectangular specimen;
b) bending test method of rectangular specimen;
c) strain method of tapered specimen;
d) strain method of dumb-bell shaped specimen.
3.2 Expose rubber specimens, held under strain or bending state by test block, to atmospheric environment or zone-containing medium for definite periods of time and evaluate their deterioration observed as evidenced by the appearance and growth of cracks on the surfaces.
3.3 Ozone concentration shall be determined in accordance with ASTM D 4575.
4 Test principle and application
4.1 When a rubber specimen is placed in an atmospheric environment or an ozone-containing medium for aging test under static strain or bending state, its surface will crack due to ozone and other factors. The direction of this crack is basically perpendicular to the stress direction of the specimen. The aging resistance of rubber may be relatively evaluated by observing the change of specimen surface cracking.
4.2 This standard is not suited for use in purchase specifications, not only because correlation with service life is uncertain, but because the testing results from duplicate specimens tested in different locations do not ordinarily give the same values. No exact relation between the testing results of the test and actual service is given or implied. This standard is principally used for comparisons of aging resistance between two or more rubber materials.
5 Apparatus for Method A - Strain method of rectangular specimen
