No abstract

The resistance of Neoprene vulcanizates to attack by ozone as measured by accelerated tests has been studied. The known superiority of Neoprene in this property was found to be affected more by compounding ingredients than previously recognized. It was found that neither the presence of accelerators nor their influence on the modulus of fully cured Neoprene vulcanizates affected ozone resistance. The addition of fillers impaired ozone resistance in proportion to the amount used. The coarse particle size fillers were particularly harmful. Petroleum base plasticizers had a negligible adverse effect, but certain of the ester and similar types were significantly deleterious. Unsaturated vegetable oils and their derivatives, as well as wood resin, are beneficial to ozone resistance. Certain softeners and extenders frequently used to promote ozone resistance so function only by virtue of the stress relaxation they induce in vulcanizates. A number of antioxidants, especially those which reduce flex cracking are powerful ozone-resisting agents, particularly when used in large quantities. Certain of the nondiscoloring type of antioxidants are harmful to ozone resistance.