Aging is one of the main reasons for the deterioration […]
Aging is one of the main reasons for the deterioration of rubber properties. Due to the different formulations and use conditions of the products, the aging process varies, so it is necessary to measure and evaluate through the aging test to assess the degree of rubber aging and its impact on performance. The aging test is a test method and test method used to evaluate the changes in rubber performance (generally, performance degradation or deterioration) before and after a certain period of time under external conditions. Commonly used rubber aging test methods are as follows.
Natural aging test
The rubber test piece is placed in a natural outdoor environment under tension, and after a long period of sun and rain, the performance changes before and after observation, measurement and comparison are observed. Although this method has high fidelity and strong simulation of the actual situation, it often takes too long and is generally suitable as an auxiliary reference, but it is impossible to complete the test in a short time and draw a conclusion.
Accelerated aging test
To obtain the aging test data in a shorter time, it is necessary to use accelerated aging test, that is, to strengthen the test conditions, accelerate the aging process, greatly shorten the test cycle, and obtain the test result-aging data faster.
Such test items are:
1. Oven heating aging test Referred to as thermal aging test, it is currently the most widely used method. The test equipment used was a heating oven. The heating temperature (usually 70 and 100) and time (usually 72 and 144h) can be set. The test piece is hung on the rotating film holder in the box. After the test, the test piece is taken out, its performance is measured, and compared with the data before aging, the aging coefficient is calculated, and the degree of damage reduction is measured. For example, the tensile strength of a rubber compound before thermal aging is 20MPa, and after thermal aging is reduced to 12 MPa, the aging coefficient is 0.6.
2. The weathering test simulates the environmental conditions when used outdoors, and the accelerated aging test is carried out on the sample in the box. The test device can reproduce the climatic conditions encountered in actual use, such as light exposure (replace with light irradiation) and rain (replace with water spray). Therefore, the accelerated aging test light source under simulation and simulation conditions uses ultraviolet light or carbon arc light. The test time can be adjusted within 10-1000 h. In addition to measuring the physical properties after the test, it is also necessary to observe the cracking of the surface.
3. The ozone aging test is used to investigate the degree of ozone damage to rubber. The test device is a closed ozone aging box. There is an ozone generator, which produces a certain concentration of ozone through the mercury lamp. The test piece accepts a certain amount of tensile deformation during the test. After a certain period of time, the depth of cracks on the surface of the sample is observed to determine the level of ozone resistance of the rubber compound.
4. The oxygen aging test test piece is placed in a metal bomb-shaped closed container, filled with oxygen, and tested under heating and pressure. The temperature is generally heated to 70 degrees. The oxygen pressure is maintained at 0.6-0.7 MPa, and the duration is selected from 24, 48, and 72 h. After the stipulated time, after parking at room temperature for 16-96 h, then compare the performance changes before and after the test.