What is the most appropriate way of finding out Glass Transition temperature from the DMA curves. And how do we know about the service temperature of a specimen from DMA interpretation ?
Peak temperature of tan delta is the glass transition temp in DMA curves.
Dear Saurabh,
Please, see first paragraph of page 3005 in the attached paper: "Above 400 K the sample reaches the dynamic glass transition characterized by decay of E'(T) and peak loss of E"(T)".
Regards,
Jose
Article Relaxation of rapidly quenched metallic glasses: Effect of t...
According to ISO 6721-11 seven different values are defined for the three typical curves from DMA measurements. As glass transition the inflection point of the storage modulus is used. But also the onset and offset of the storage modulus can be very usefull and give you also some information about the broadness of the transition proces which can be compared for different materials.
The peak in loss modulus is up to my experience often rather close to the inflection point of the storage modulus. The peak in tan d lies always considerably higher.
The other two points (start and end point of storage modulus) are rather extreme values which could be understood as threshold values to ensure that the effect of glass transition is avoided (at least at the frequency of the experiment).
Overall it is always difficult to express the complex glass transition with only a single temperature. For complex decisions the overall process must be considered plus the frequency dependence.
The service temperature range depends mainly on the application. A structural part should remain below tg to avoid to get soft but e.g. a dynamic seal should stay above tg to maintain it`s elasticity.
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