Significance and Test Method
The ageing of elastomers involves a variety of processes that chemically or physically change or degrade the vulcanised rubber. The damage to elastomers caused by ageing is irreversible, thus not reversible, and makes the materials unusable after some time.
Ageing processes are triggered or accelerated by various factors. High temperatures are among the critical factors and can increase the influence of contact media, gases and radiation. The heat resistance of an elastomer is therefore one of its most important properties.
Ageing tests attempt to simulate the deterioration processes taking place in a kind of time-lapse in the laboratory. Compared to the everyday use of the components, higher temperatures are often used here to accelerate reactions.
Significance for Application Technology
Based on the results of heat ageing tests, statements can be made about the temperature resistance of a material without the influence of contact media. In addition, the results can be used to estimate the expected service life of the tested materials under certain conditions of use. In combination with other tests, the results of heat ageing also allow an evaluation of the compounds and processing quality of elastomers.
The Heat Ageing Test
Different methods of heat ageing, hence artificial ageing, of rubber and elastomers are defined, among others, in the standards ISO 188, DIN 53508, ASTM D 573 or ASTM D 865.
During heat ageing, a standardised test specimen is exposed to hot ambient air for a defined period of time and at a defined temperature. Depending on the method, this is done with or without a supply of fresh air.
The supply of fresh air, that is, additional oxygen, during the test causes additional stress on the specimen and usually leads to stronger or faster reactions. In contrast, reactions with atmospheric oxygen in a closed atmosphere without additional air supply can come to a standstill after the available oxygen has been fully used. Both test variants have their justification with regard to technical applications.
The actual evaluation of the materials is done using some important, physical basic properties, for example hardness or tensile strength and elongation at break. These are tested before and after the heat ageing process and the results are compared with each other.
Downloads
You can find out more about heat ageing, testing and practical application in our technical reports:
Heat ageing of elastomers
In this report, you will learn more about the ageing processes of rubber materials, the testing principles and special features of heat ageing and the practical benefits of the tests. In addition, we inform you about current standards and the test methods defined therein.
100 Years Heat ageing as per W.C. Geer
The article describes the development of the heat ageing test method.
Thermal overload, overheating (long version)
Rarely is temperature alone the problem. In most cases, it is the wrong combination of temperature and time. In this technical report, you can find out more about the damage caused by thermal overload on elastomers and its practical effects. We give recommendations on testing and advice on how to avoid thermal damage.
Thermal overload, overheating (short version)
Rarely is temperature alone the problem. In most cases, it is the wrong combination of temperature and time. In this technical report, you can find out more about the damage caused by thermal overload on elastomers and its practical effects. We give recommendations on testing and advice on how to avoid thermal damage.
