DSC measurements can be used to investigate the usable temperature range for sealing rings. The lowest usable temperature of the material is defined by the temperature at which the sample passes from a glassy, brittle state to a rubbery-elastic state. This is the case at and above the glass transition. The glass transition temperature as measured by DSC can therefore be regarded as a characteristic value that defines the lowest possible application temperature of the material. The measurement curves of various commercial sealing rings are presented.
Several commercially available sealing rings made from different elastomers:
MQ methyl silicone rubber
NBR acrylonitrile-butadiene rubber
FPM fluoroelastomer
EAM ethylene-vinyl acetate copolymer
Measuring cell: DSC822e with liquid nitrogen cooling option
Pan: Aluminum 40 ul, pierced lid
Sample preparation: Slices of the sealing rings of approx. 10 mg
DSC measurement: Heating from 100 °C to 25 °C at 10 K/min
Atmosphere: Nitrogen, 50 ml/min
The sealing rings differ in their glass transition temperature. The lowest temperature at which they should be used is always at least about 10 K above their glass transition temperature. The silicone rubber sealing ring does not exhibit a glass transition in the temperature range measured. A melting peak is observed between –70 °C and –40 °C. The crystallization limits the range of applications for this material.
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Sealing materials can be rapidly and easily characterized by DSC. The glass transition temperature is usually the crucial factor for the application of sealing materials in the lower temperature range.
Determination of the Usable Temperature Range of Sealing Rings | Thermal Analysis Application No. HB 491 | Application published in METTLER TOLEDO TA Application Handbook Elastomers Volume 2