To obtain the maximum effectiveness from antiozonants such as the N,N′-dioctyl-p-phenylenediamines in any given stock, information to date indicates the desirability of: (a) The selection of proper antiozonant-polymer combination. (b) The use of low-oxygen-content reinforcing blacks (thermal or furnace rather than channel). (c) The use of a thiazole-accelerated sulfur cure. (d) The proper design of product to avoid cured-in strain and sharp edges. The choice of antiozonant concentration will depend in part on strain, ozone concentration, and temperature to be encountered in service, as well as the type of service—static or dynamic—and the desired crack-free life of the article. Only through a consideration of all these factors can the maximum results from chemical antiozonants be achieved.
Core sampling filter media can be a difficult and time‐consuming task if a large amount of media must be removed. However, “wet‐or‐dry” vacuum cleaners can reduce the time and effort spent. This technique was developed in the process of obtaining core samples of anthracite coal from a full‐scale filter bed for a pilot‐plant project.
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