Dynamic Ozone Chamber Test

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]. 

The test procedures selected for dynamic ozone chamber tests - with striking differences in specimen dimensions and their deformation due to alternating load, as well as in the evaluation of occurring ozone cracks - include ... 

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. 

HilF reported pollutant uptake values for a number of gaseous pollutants, including ozone and PAN, with alfalfa as his test organism (Table 11-26). These values were obtained with a dynamic, but closed, exposure facility. Uptake was determined by the amount of pollutant needed to maintain a constant chamber concentration over an alfalfa bed. Uptake values, expressed on the basis of leaf area, reflect the effect of the plant canopy on the exchange of gases within the canopy and do not... 

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