Resistance to Sun, Weather, and Ozone

Cold water preserves natural rubber, but if exposed to the air, particularly in sunlight, rubber tends to become hard and brittle. It has only fair resistance to ozone. Unlike the s)mthetic elastomers, natural rubber softens and reverts with aging to sunlight. In general, it has relatively poor weathering and aging properties. 

Natural rubber offers excellent resistance to most inorganic salt solutions, alkalies, and nonoxidizing acids. Hydrochloric acid will react with soft rubber to form rubber hydrochloride, and therefore, it is not recommended that natural rubber be used for items that will come into contact with that 

Unvulcanized rubber is soluble in gasoline, naphtha, carbon bisulfide, benzene, petroleum ether, turpentine, and other liquids. 

Refer to Table 5.6 for the compatibility of natural rubber with selected corrodents. 

Compatibility of Natural Rubber with Selected Corrodents 

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Neoprene displays excellent resistance to sun, weather, and ozone. Because of its low rate of oxidation, products made of neoprene have high resistance to both outdoor and indoor aging. Over prolonged periods of time in an outdoor environment, the physical properties of neoprene display insignificant change. If neoprene is properly compounded, ozone in atmospheric concentrations has little effect on the product. When severe ozone exposure is expected, as for example around electrical equipment, compositions of neoprene can be provided to resist thousands of parts per million of ozone for hours without surface cracking. Natural rubber will crack within minutes when subjected to ozone concentrations of only 50 ppm. 

EA elastomers have extremely good resistance to sun, weather, and ozone. Long-term exposures have no effect on these rubbers. 

Ethylene-propylene rubber is particularly resistant to sun, weather, and ozone attack. Excellent weather resistance is obtained whether the material is formulated in color, white, or black. The elastomer remains free of surface crazing and retains a high percentage of its properties after years of exposure. Ozone resistance is inherent in the polymer, and for all practical purposes, it can be considered immune to ozone attack. It is not necessary to add any special compounding ingredients to produce this resistance. 

Silicone and fluorosilicone rubbers display excellent resistance to sun, weathering, and ozone. Their properties are virtually unaffected by longterm exposure. 

Ethylene-chlorotrifluoroethylene is extremely resistant to sun, weather, and ozone attack. Its physical properties undergo very little change after long exposures. 

These rubbers have excellent resistance to sun, weathering, and ozone. 

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