Tan delta and curve wisth

[CatRachel]

Hi,
I'm trying to analyse DMTA results and, in the process describe the definition of tan delta and what the width of the tan delta peak represents.
My polybutadiene samples have been artifically aged and shown a decrease in Tg (tan delta peak), a broadening of (85%max) tan delta peak width amd a rightward shift on the temperature axis.

Does anyone have ny ideas how this could be explained and definitions of the changes described?
Thanks in advance

 

[ThermOGreen]

Basically tan delta can be used to chartacterize the modulus of the material. Delta should range between 0° and 90° and as delta approaches 0° it it also approahes a purely elactic behaviour. As delta approached 90° the material approaches a purely viscous behaviour.
The tan of delta is defined below:

tan(delta) = E"/E'

where

E" = storage modulus
E' = loss modulus

You modulus of elasticity (E*) can then be calculated as:

E* = sqrt(E'^2 + E"^2)

 

[Demon3]

I can try to help. The peak of the tan delta occurs at Tg although that will in turn depend on the testing frequency. As you age the polybutadiene should cross-link and shift the Tg and tan delta peak to higher temperatures.

The height of the peak may decrease signifying that the material is more elastic than before.

Lastly if the width of the peak increases that should mean that your material is less homogeneous than it was before, i.e. perhaps areas with higher and lower degrees of cross-linking.

Please note I am far from an expert on DMTA but this is how I would interpret what you described.