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Questions about Tangent Delta-Temprature test

3 years 3 weeks ago #2846 by Mr David Fei
Dear All,

I have a principle question about the Tangent delta test of enamel wires.

I have checked all the data I can find and still get no answers. Please help me to find out the answer!

We always do the tangent delta - temperature test to judge the curing degree. (In my case I use DSE Test Solution's TD-5 as tester)

Now, my questions are:

1. What is the exact meaning of the transition temperature?

2. Why Polyester & Polyesterimide have 2 transition points, but Polyurethane and Polyamideimide often have 1 transition point?

3. If the D-value means 'dielectric loss factor' than why the D-value perform up-down-up when the insulation varnish is polyester or Polyesterimide? What happened when the temperature goes after the 1st transition point and before 2nd point?

I really need your technical advise. I've been in this profession for 3 years and nobody can give me a specific answer.

Thanks for your help!


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3 years 3 weeks ago #2849 by Richard Burke
Not that hard to find an answer.
Transition temperate is the temperature at which a solid material become plastic or fluid. The cut thru test is an example: you cross two wire on each other at 90 degree angles and place a weight on the intersection and then heat the samples in a test device. When the coating begins to reach it transition temperature, the weight on the wires pushes one wire into the other and as the coating continues to soften it thins until the two conductors touch.

Different materials have different transition temperatures and some might have two - low temperature enamels have a less complex chemical structure than higher temperature enamels.

Not sure where you are and what type access to data you have but this information was easily found on the internet.

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3 years 3 weeks ago #2853 by Mr David Fei
Dear Richard,

Thanks for your reply.

I also studied a lot and find out the transition point is highly correlated to glass transition temperature. However, still left some questions as: why PU/PAI wire usually shows 1 transition points but PE/PEI shows 2 points?

Some literatures claimed that is the property of isocyanate but none of them explained clearly nor with any chemical schema to prove it. So I still very confused of it.

If that is not so bother could you please explain this for me? Or just advise me some reference that I can find out the answer of the reason to show different figure from different materials?

With my best thanks & regards


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2 years 10 months ago #2878 by Richard Burke
I am not a chemist and cannot explain the finer points of chemistry. I assume you are talking about urethane and amidimide when you say PU/PAI and polyester and poly esterimide when talking about PE/PEI. If that is the case, I think what you are experiencing is due to the fact that the PE material is a more complex material (chemically) than the PU. It has higher thermal properties such as cut thru, and higher dialectic values, etc. I think what you are seeing is one component of the PE start to transition and then the others. Have you ever stretched a piece of copper rod and then steel rod on a tensile tester? The copper stretches until it breaks with an uninterrupted curve. Steel curves, drops back, and then the curve starts again.

Contact your enamel supplier for detailed information. They should be happy to provide specific details.

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