Monday, April 20, 2009

Silicone Rrubber MQ MPQ MVQ and MPVQ

As you can see, a number of symbols have been designated for significant variations within the silicone rubber family. The reader may refer to ASTM D 1418 for abbreviations for elastomeric materials. Since all of the symbols for silicone rubber end in Q, this is the convention that will be used for silicone rubber in general. Most elastomers have a carbon main chain, while Q has a silicone oxygen backbone. Silicone has an upper continuous heat aging temperature in the region of 205°C. Caprino and Macander give a table of estimated service life for Q as follows: 40 years at 90°C, 2-5 years at 200°C and two weeks at 315 °C. Moisture, such as might be found in a poorly ventilated environment, can be a problem at high temperature. Silicone is among the best elastomers for both high and low temperature resistance. PVMQ heads the low temperature list at around -100°C. Silicone rubber has excellent ozone, weather resistance and electrical insulation. Like CR, Q has a measure of flame retardant ability. Mechanical properties such as tensile strength, are low, but change very little when measured at higher temperatures; at 150°C, it is catching up with other elastomers. Oil resistance is about the same as that of CR, acid and alkali resistance are not good. Applications include aerospace, medical, food contact, and automotive ignition cable. The cost of the raw gum elastomer is higher than any of the rubbers mentioned so far.

Reference: An Introduction to Rubber Technology by Andrew Ciesielski 1999

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