This standard specifies the aging test method for vulcanized rubber in a humid hot air environment. This standard is applicable to the evaluation of the resistance of rubber to humid and hot aging. GB/T 15905-1995 Test method for humid and hot aging of vulcanized rubber GB/T15905-1995 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Test method of damp heat aging for vulcanized rubber
Rubber , vulcanized-Test method of damp heat aging
GB/T15905---1995wwW.bzxz.Net
This standard adopts the damp heat test part of the international standard ISO4611-1987 "Plastics-Determination of the effects of damp heat, water mist and salt spray" in a non-equivalent manner.
1 Subject content and scope of application
This standard specifies the aging test method for vulcanized rubber in a humid hot air environment. This standard is applicable to the evaluation of the damp heat aging resistance of rubber. 2 Reference standards
GB/T528 Determination of tensile properties of vulcanized rubber and thermoplastic rubber GB2941 Standard temperature, humidity and time for environmental conditioning and testing of rubber specimens GB9865 Preparation of vulcanized rubber samples and test specimens GB10586 Technical conditions for wet heat test chambers
3 Summary of methods
The rubber specimens are exposed to a humid hot air environment, subjected to the effects of hot air and water vapor, and the changes in the performance of the specimens are detected at a predetermined time, thereby evaluating the wet heat aging resistance of the rubber. 4 Test apparatus
The test apparatus should use a wet heat test chamber (or room) that complies with the provisions of GB10586. Generally, the following conditions should be met: a. There should be enough space to place the specimens, and the volume of the work chamber should not be less than five times the total volume of the specimens, b. It is equipped with an automatic constant temperature device, and the temperature uniformity of the working room is not more than 1℃, and the temperature difference is allowed to be ±2℃. It is equipped with an automatic constant humidity device, and the relative humidity difference of the working room is allowed to be 2%. c.
d. It is equipped with a continuous blowing device and ventilation holes, and the average wind speed of the working room is not more than 1m/s. The test instruments and methods for temperature, humidity and wind speed of the wet heat test chamber can refer to the relevant provisions of GB10586. 5 Samples
5.1 The preparation of the sample shall comply with the relevant provisions of GB9865. 5.2 The shape and specifications of the sample shall be selected according to the evaluation index and the requirements of the corresponding test standards. For example, for the test sample for evaluating the change of tensile properties, the dumbbell-shaped sample specified in GB/T528 should be used. 5.3 The number of samples can be determined according to the test items, test cycles and the requirements of the corresponding standards. Generally, there should be no less than three valid samples for testing each performance.
Samples that do not meet the requirements of the standard cannot be put into the test, and the test results of samples of different specifications cannot be compared. Approved by the State Bureau of Technical Supervision on December 20, 1995, and implemented on August 1, 1996
6 Test conditions
GB/T 15905-1995
6.1 The test environment includes conditions such as test air temperature and relative humidity, which may be based on the conditions of use of the rubber product or the agreements of relevant parties, or may be selected according to the following environments: 6.1.1 Constant test environment
Constant temperature: 40±2℃
Relative humidity: (93±)%
If an accelerated aging test is performed, the recommended temperature is 70±2℃. 6.1.2 Alternating test environment
Alternating temperature: the lower limit is 25±3℃, the upper limit (select one of them) is a.40±2℃
b.55±2℃
Relative humidity: (93±3)%
The upper and lower limits of temperature are raised and lowered in an alternating cycle of 12h+12h. From 12h±30min from the start of the cycle, it should be kept within the specified temperature range. The alternating time of temperature rise and fall can be controlled within 3~~6h. The relative humidity should not be less than 90% in the first 15min and the last 15min of the temperature alternation, and should be (93±3)% at other times. 6.2 The test cycle and period can be determined according to actual needs or the agreement of relevant parties, or the following time can be used as the test cycle: a. 24h, or multiples of 24h;
b. 7d, or multiples of 7d.
6.3 Test water
The water used to adjust the humidity of the wet heat box or to contact the sample should be distilled water or deionized water with a pH value of 6 to 7. 6.4 Treatment conditions before and after the test
6.4.1 Unless otherwise specified, the sample should be conditioned in accordance with the relevant provisions of GB2941 before the test. 6.4.2 After the test, the sample can be treated according to the technical requirements of the product or the agreement of the relevant parties. Generally, the following treatment is performed: a. After the sample for direct evaluation of moisture performance is taken out of the hot box, it should be immediately placed in a closed container with steaming water or deionized water at the bottom (the sample does not contact water), and the sample performance can be tested after being treated at the temperature specified in GB2941 for 4 hours. b. For samples for relative performance comparison, after exposure in the wet heat box, the environment should be conditioned in accordance with the relevant provisions of GB2941 before performance testing.
7 Performance testing and evaluation
The items for testing the performance of the sample should be selected according to the use characteristics and test requirements of the rubber product, or determined by the agreement of the relevant parties. If there is no specific provision, the mechanical properties, electrical properties, or changes in appearance, volume, etc. of the sample can generally be tested. The test method for the performance of the sample should be carried out in accordance with the relevant standards. For example, the tensile properties of the sample should be measured in accordance with the relevant provisions of GB/T528. If the moisture content of the sample is tested, it should be carried out immediately in accordance with the relevant regulations while the sample keeps the original moisture content as much as possible.
It is recommended to use the tensile strength and elongation of the sample as the main evaluation indicators. 8 Test steps
8.1 First, treat the sample according to the provisions of 6.4.1, and then measure the initial properties of the sample (including the geometric dimensions or appearance of the sample). 8.2 Start the wet heat box to make it reach the specified test conditions. After the temperature and humidity are stable, the sample is put into the test, and the test time is calculated and recorded.
8.3 The specimens shall be hung freely or laid flat in the effective working room of the damp heat box for exposure. The specimens shall not overlap or touch each other, and the spacing between them shall not be less than 5mm. The distance between the specimen and the box wall shall not be less than 70mm. 544
GB/T15905--1995
8.4 After the test reaches the cycle, the specimen shall be quickly taken out from the damp heat box, and immediately processed according to the provisions of 6.4.2, and then the performance of the specimen shall be tested.
After the performance test of the specimen is completed, if it is necessary to continue the test, the specimen shall be placed back into the damp heat box in its original state for exposure until the end of the test. Note: It is best not to test the specimens containing volatile substances or easily migrated antioxidants together in the same damp heat box to avoid mutual contamination and affect the test results.
9 Test results
The test results can be expressed by the performance values ​​(median) of the specimens before and after aging, or the rate of change of the aging performance of the specimens. The rate of change of the aging performance of the sample is calculated as follows: A-O
Where: P--rate of change of the aging performance of the sample, %; O---measured value of the performance of the sample before aging, A--measured value of the performance of the sample after aging. The change of hardness can be expressed by the difference between A and O. 10 Test report
The test report includes the following contents:
Test purpose and requirements;
reference to the code and name of this standard,
name, source, specification and quantity of the sample; specification and model of the wet heat test chamber,
selected test temperature and relative humidity and other environmental conditions, test items, evaluation indicators and test methods: test time, period and test cycle;
test results and others.
Additional remarks:
This standard is proposed by the Ministry of Chemical Industry of the People's Republic of China. This standard is under the jurisdiction of the Rubber Industry Research and Design Institute of the Ministry of Chemical Industry. This standard is drafted by the Institute of Synthetic Materials of the Ministry of Chemical Industry. The main drafter of this standard is Chen Jingsheng.
This standard is entrusted to Beijing Rubber Industry Research and Design Institute for interpretation. 545
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