Fluorocarbon elastomers epichlorohydrin elastomer

The above criteria were employed to select several commercially supplied Class PS elastomers for laboratory screening by employing selected tests taken from National Bureau of Standards NBSIR 77-1437(j4) and ANSI/ASTM D-3667-78 specifications for "Rubber Seals Used in Flat-Plate Solar Collectors". Four silicone, three EPDM, two fluorocarbon, three epichlorohydrin, one ethylene-acrylic, one polyacrylic, one chlorosulfonated polyethylene, one bromobutyl and two butyl rubbers were studied in these screening tests. These materials are identified in Table I and those compositions which were revealed by their manufacturers are shown in Table II. Undoubtedly some materials which should have been included were omitted however, we hope that this sampling will provide an indication of the applicability of a wide range of materials for use as sealants in thermal solar collectors. 

Figure 4. Volume change of elastomers as a function of MTBE concentration in Indolene HO-III. Key o.fluorocarbon , epichlorohydrin homopolymer a, chlorosulfonated polyethylene and o, EPDM.

Qualitatively MTBE Is estimated to have an overall solubility parameter value close to that of Indolene, but has higher polar and hydrogen bonding forces. As a result polar polymers such aa fluorocarbon, epichlorohydrin homopolymer and chlorosulfonated polyethylene tend to swell to a greater extent In MTBE rich mixtures, while nonpolar EPDM elastomer swells to a lesser extent In these mixtures. The very large swell of the fluorocarbon In MTBE Is not surprising since other ethers such as diethyl ether and dioxane are known to swell the fluorocarbon to a large extent [3]. 

Saturated elastomers are often cured by peroxide, often aided by catalysts. These include chlorinated polyethylene, fluorocarbon, acrylic ester, epichlorohydrin, polysulfide, polyurethane, and silicone. The peroxide radical abstracts an unstable hydrogen from the polymer, leaving a polymer radical, and then polymer radicals couple to produce C-C cross-links. 

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