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Low Temperature
Property:
Low Temperature
Method of Measurement:
A variety of methods are used for determining the low temperature characteristics of rubbers. These fall into two groups a) measuring brittleness at low temperatures by impact testing and b) measuring the modulus at low temperatures. Different test jigs are required for each method, as described in the relevant specifications.
ASTM D2137 measures brittleness. ASTM D1053 and BS 903 Pt A13 measure the modulus characteristics. Two simple tests are a "bend" test and a "retraction" test. In the "bend" test a sample 25mm wide x 100mm long is bent around a mandril which is usually of a diameter 10 x the thickness of the test piece (typically 25mm dia). If the sample bends without cracking it is deemed to be "flexible at this temperature". In the "retraction" test, the sample is stretched and frozen in this position below its glass transition temperature (i.e. the temperature at which the rubber becomes rigid). The temperature is then raised gradually or in steps and the temperature at which the rubber retracts is recorded.
It should be noted that rubber passes from a rubbery phase into a "leathery" phase and then into it’s "glassy" phase as it is cooled. Different methods can therefore give rise to different values according to their sensitivity to this "leathery" phase.
ASTM REFERENCE:
D2137
D1053
D1329
BS REFERENCE:
BS903 Part A25
BS903 Part A29
BS5294
ISO REFERENCE:
ISO/R812*
ISO2921**
* technically equivalent
** identical
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