Low Temperature Gaskets

In New England we are used to very low temperatures. These temperatures during the dead of winter can range from -40 Fahrenheit to 45 F. We have two types of people in New England: those who love the cold and those who hate it. Whatever the case, we all tolerate it. Rubber materials are akin to New Englanders in this regard.

Low Temperature Gaskets refer to gaskets that usually tolerate sub-zero temperatures. The glass transition temperature of an elastomer is not quite an exact number, but it gives an idea of where the rubber turns to a leathery-like texture. As temperature drops, the elastomer tends to toughen, which then makes the rubber feel differently. The reason that the rubber turns brittle is because it begins to crystallize at lower temperatures. It is good to note that the glass transition is generally reversible, unlike heat aging. The glass transition temperature of an elastomer is essentially when the polymer backbone loses its flexibility. The glass transition temperature is important in the rubber industry because it gives an idea of what temperature the rubber will not deform, so the rubber will not seal as before. Silicone polymers have a number of advantages over organic rubbers, such as resiliency at extremely low temperatures. This is because silicone has an inherently flexible backbone even at low temperatures.The glass transition temperature is normally denoted by Tg. Low temperature is important enough in rubber products that ASTM D2000 has a suffix for it. Under ASTM D2000, the suffix for low temperature testing is F. The suffix F indicates that the vulcanizate must be tested IAW (in accordance with) the specified test methods and is frequently used in ASTM D2000 when suffixes are required. F17 is the suffix most frequently required; this indicates that ASTM D2137 Method C is required.

There are many tests for testing low temperature flexibility. The common tests required for testing for flexibility at low temperatures are ASTM D1329 and ASTM D2137. Under ASTM D1329, there are two measurements that are made. The first measurement is TR10, which indicates the temperature at which the ‘vulcanizate’ retracts 10%. You may have guessed that TR70 is the temperature at which the ‘vulcanizate’ retracts 70%. TR10 has been correlated with low temperature compression sets, and TR70 has been correlated with the brittle point.

Naturally, there are rubber polymers that have an inherent ability to maintain elasticity at lower temperatures. Some of the elastomers are actually famous for being able to tolerate extremely low temperatures. These rubbers include: fluorosilicone, silicone, nitrile rubber (varies with the ACN content) and EPDM (EPDM’s low temperature properties tend to vary with the content of ethylene). NEDC has been providing low temperature gaskets for the past 30 years to the aerospace, military, and energy markets. NEDC can provide low temperature rubber materials as sheets, die cut, o-rings, and waterjet cut. If you have any questions on gaskets or materials that can withstand extremely cold temperatures, feel free to contact sales@nedc.com.

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