Why is the flow behaviour or viscosity important in the case of polymer?

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Discussion Overview

The discussion centers on the importance of flow behavior and viscosity in polymers, particularly in relation to their structure, bonding, and applications in various products. The context includes theoretical insights, experimental observations, and practical implications in polymer processing.

Discussion Character

  • Exploratory
  • Technical explanation
  • Experimental/applied

Main Points Raised

  • Some participants propose that viscosity provides insights into the structure and bonding of polymers, influencing their processibility into products like plastics and elastomers.
  • Others mention that the manipulation of polymers for various applications remains an important area of research.
  • A participant shares an experimental experience measuring the viscosity of polystyrene in toluene, linking viscosity to molecular weight through a specific relationship.
  • It is noted that the viscosity is influenced by the molecular coiling of the polymer, with a constant used in calculations reflecting this property.

Areas of Agreement / Disagreement

Participants generally agree on the significance of viscosity in understanding polymer behavior and applications, but the discussion includes various perspectives on its implications and the details of experimental methods.

Contextual Notes

The discussion references specific experimental conditions and relationships that may depend on particular assumptions or definitions, such as the constant used in viscosity calculations and the accuracy of molecular weight measurements.

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Why is the flow behaviour or viscosity important in the case of polymer?

This question is given when we had lecture about flow behaviour, viscosity, and rheology.

Thanks a lot!
 
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Viscosity is an important characteristic of polymers because it gives an insight to the structure and in turn, the degree of bonding in the structure, and how well the structure is formed. Flow behaviour determines the processibility of the polymer into different products like plastics, elastomers etc It's atill an important research area as to how to manipulate polymers for various applications.

E.g. of such applications http://www.phy.bris.ac.uk/research/polymers/flow.html
 
Mr.cute, are you a student taking course MAT705 in Queen Mary College? I meet the same question in the exam.
 
Well, in a physical chemistry lab this semester we dissolved polystyrene in toluene and measured the viscosity, from which we were able to derive the molecular weight of the polymer from the relationship n = M^a (where n is the viscosity coefficient, M was the molar mass and a was a constant equal to about ~0.75 if I remember correctly. We measured the molecular weight to about 100,000 g/mol, which was pretty accurate.

As atomic blast suggested, the viscosity is influenced by how tightly "coiled" the molecule is - that is what the consant "a" is a measure of.
 

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