Ozone Resistant Neoprene Compound

Table 3.3 Typical ozone resistant Neoprene compound for cell house application ...

Mueller and Stickney at Battelle revealed very substantial compounding costs for protection against photochemical oxidants. Table 13-14 summarizes the results of an analysis based on responses to a questionnaire. These costs include the introduction of such ozone-resistant polymers as butyl, neoprene, EPDM, Hypalon, and polysulfide. Fair... 

Processing ndProperties. Neoprene has a variety of uses, both in latex and dry mbber form. The uses of the latex for dipping and coating have already been indicated. The dry mbber can be handled in the usual equipment, ie, mbber mills and Banbury mixers, to prepare various compounds. In addition to its excellent solvent resistance, polychloroprene is also much more resistant to oxidation or ozone attack than natural mbber. It is also more resistant to chemicals and has the additional property of flame resistance from the chlorine atoms. It exhibits good resiUence at room temperature, but has poor low temperature properties (crystallization). An interesting feature is its high density (1.23) resulting from the presence of chlorine in the chain this increases the price on a volume basis. 

Butyl rubber like Hypalon, Neoprene or nitrile rubber is a speciality polymer which can be compounded for a soft, deformable elastic vulcanisate similar to the other elastomers, but having certain distinctive characteristics, like low permeability to all gases and resistance to ageing and ozone cracking. Butyl has poor oil resistance and medium low temperature flexibility. 

In the presence of light, halogens attack both vulcanised and unvulcanised butyl rubber. Whether vulcanised or unvulcanised the effect of the reaction is to produce rapid deterioration in molecular weight. A strip of butyl vulcanisate suspended in bromine gas degrades rapidly. In a few minutes the specimen becomes fluid enough to drip to the bottom of the vessel. Chlorosulfonated polyethylene is resistant to ozone being better than Neoprene and butyl rubber compounds [18]. 

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. 

The rotary seal compound is sticky during mixing, but the O ring compound is not. The activator RCD 2098 is a zinc chloride/MBTS complex. Zinc diethyl dithiocarbamate and other activators containing zinc may also be used, but they are less effective. These polyurethanes have outstanding abrasion resistance, similar to neoprene in ozone and weather resistance, and comparable to nitrile rubbers in oil and fuel resistance. Heat aging is excellent up to 250°F (121°C), and the brittle point is —90°F (—68°C). 

Neoprene provides a versatile elastomeric base in the formulation of solvent based adhesives. Properly compounded adhesives are resistant to degradation from exposure to heat, sunlight, ozone, water, oils, and chemicals. Neoprene can be dissolved in many solvent blends to give adhesive solutions which are stable for extended periods of time. Solvent selection, therefore, allows a great deal of variation in adhesive viscosity and drying rate. Other com-... 

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