Static Ozone Chamber Test

The static ozone chamber test permits adjustment of ozone concentration (0.5 to 2.0 ppm) and temperature (20 to 50°C) as well as relative humidity (10 to 90%) besides numerous strain levels for the rubber specimens the typical loading time ranges from 2 to 96 hours. The corresponding materials and product standards provide recommendations for the use of certain testing conditions the atmospheric conditions in the ozone chamber should, however, be tuned as closely as possible to the crack resistance of the particular elastic material short-term loading at a low ozone concentration and temperature in the case of crack prone materials, a high ozone concentration and temperature over several days for relatively ozone resistant rubbers. 

Ozone chamber testing of materials deformed by alternating load has - for various reasons - never become established in practice to the same degree as testing under static mechanical conditions. It is simpler, more focused, and easier to subject rubber products to practical testing by mounting them in a vehicle or in an appropriate mechanical apparatus than to subject rubber specimens to the dynamic ozone chamber test in the testing chamber [232]. 

Since ozone attack on rubber is essentially a surface phenomenon, the test methods involve exposure of the rubber samples under static and/or dynamic strain, in a closed chamber at a constant temperature, to an atmosphere containing a given concentration of ozone. Cured test pieces are examined periodically for cracking. 

In dynamic testing of ozone resistance, a fabric-backed vulcanized rubber specimen is continuously flexed in the ozone chamber over a roller. The fabric backing is in the form of a belt. Any protective chemical films (e.g., certain waxes and antiozonants) that might build up on the surface of the specimen in static testing are quickly broken by the continuous flexing. ASTM test method D 1149 covers static testing and D 3395 covers dynamic testing in a controlled ozone atmospheres. 

In addition to the weathering tests for elastomers described in Section 2.2, testing ozone resistance is significant for rubber products. Here, parts molded from rubber are stored statically (tensile strain) or dynamically (alternating strain) in an ozone chamber at a specified strain, temperature, humidity, and ozone concentration. Subsequently, their ozone resistance is evaluated based on the resulting crack formation. 

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