capillary rheometer

[AgeOfEmpire]

Hi,

I will study with a capillary rheometer for learning rheological properties of some polymers.But I don't know this system very well.I read some article and some books about capillary rheometer.And I didn't understand some point.
For example ,why polymers seems melt fracture properties at high shear rate?.

And I will mount a pressure transducer end of the barrel to measure pressure losses at this region.But I am not sure Where is correct point for mounting transducer.

If you deal with capillary rheometer or rheology ,could you give some information about these.
Thanks for your interest

 

[plastx]

A capillary rheometer has the ability to subject polymers to very high shear rates by applying force and moving the material through a very small orifice. Some polymers have a top end of how much shear they can withstand. If that top end is exceeded the molecules can no longer slide by each other as they enter and exit the orifice and instead the chains start to break down.

Manufacturers mount the pressure transducers just above the die. The bottom of the transducer should be about 3mm above the die.