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Luca Vicenzutto (Vice)
Posted on Wednesday, September 29, 2004 - 2:03 am:   

Dear All!
One of my colleagues has developed a calibration in order to measure viscosity of polymers.
May I have your comments about this?
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Bruce H. Campbell (Campclan)
Posted on Wednesday, September 29, 2004 - 5:24 am:   

Luca,
It appears to me that viscosity by chemometric NIR is a secondary approach. That is, the viscosity is determined by the constituents and their amounts. As a general rule, secondary approaches require more calibration samples than primary ones, so your colleague should be aware of this and ensure a large number of calibration samples were used.
Bruce
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hlmark
Posted on Wednesday, September 29, 2004 - 5:38 am:   

Luca - the viscosity change is presumably related to the average chain length, i.e., the degree of polymerization. Your friend should know the chemistry of his polymer and therefore know the changes in the bonds involved. It would behoove him, therefore, to try to ascertain the absorbances associated with those bonds, and use those as his primary predictor variables. This tends to be difficult in the NIR, but if he can do this he will gain much confidence in his calibration model.

Howard

\o/
/_\
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Stephen Medlin (Medlin)
Posted on Wednesday, September 29, 2004 - 9:19 am:   

I did a feasibility study in the past looking at intrinsic viscosity in a polymer via diffuse reflectance. It worked because there was end group information in addition to polymer length/structure. It is a difficult measurement. One thing that we discovered is that temperature control of the pellets was essential along with very good homogenization of sample presentation to the instrument.

Stephen
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Fons Bruyninckx
Posted on Friday, October 29, 2004 - 3:05 pm:   

If the material is a liquid and this liquid is a mixture of different components all being of the same chemical structure but with a different molecular weights (from 250 --> +/-1000), is it than still possible to build models to measure viscosity via NIR?

P.S. : The concentrations of the various components can be different in such a way that the visco can vary between 200 and 800 mPas (at 25 Deg)

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