Why are polymer solutions viscous?
The more concentrated a polymer solution, the more large molecules you have exerting drag and interacting with each other. Higher concentration leads to a higher viscosity measurement.
Why is viscosity important in polymers?
Viscosity is an important characteristic for all materials, especially polymers. For liquids, viscosity will influence flow characteristics, heat transfer, and mass transfer. For polymers, viscosity is used as a measuring stick. Primarily used for higher viscosity polymers, the melt index is a common testing method.
How do you make polymer solutions?
A process for the preparation of a polymer solution comprises the steps of: mixing a polymer with a solvent to swell the polymer in the solvent; cooling the swelled mixture; and then warming the cooled mixture to dissolve the polymer in the solvent.
What does a viscometer measure?
A viscometer (also called viscosimeter) is an instrument used to measure the viscosity of a fluid. For liquids with viscosities which vary with flow conditions, an instrument called a rheometer is used. Thus, a rheometer can be considered as a special type of viscometer.
When measuring the viscosity of a polymer solution what factors would impact the accuracy of measurement?
Because the impact of a polymer on solution viscosity is determined by the volume that it occupies a polymer with a high IV, a larger volume per unit mass, will have a greater impact on solution viscosity than one with a lower IV, all other parameters being equal.
What makes a solution viscous?
Viscosity is governed by the strength of intermolecular forces and especially by the shapes of the molecules of a liquid. Liquids whose molecules are polar or can form hydrogen bonds are usually more viscous than similar nonpolar substances. Liquids containing long molecules are invariably very viscous.
What is viscosity of a polymer?
The measurement of the viscosity of polymer solutions in organic solvents gives us a value that is directly related to the molecular mass of the polymer. In other words, the higher the viscosity, the higher the molecular weight, although the correlation is not direct.
What is viscosity in polymers?
What is dilute solution viscometry?
Dilute Solution Viscometry (DSV) directly measures the relative viscosity of dilute polymer solutions. The difference in pressure drop between the two capillaries is measured and used to calculate the relative viscosity of the two solutions. Intrinsic viscosity can be calculated directly from the relative viscosity.
How is the viscosity of a polymer solution measured?
In this method, the viscosity of polymer solution is measured, and the simplest method used is capillary viscometry by using the Ubbelohde U-tube viscometer. In this method, both the flow time of the polymer solution (t) and the flow time of the pure solvent ( t0) are recorded.
Why does the viscosity of a viscometer decrease?
An explanation of the sharp decrease in viscosity could be the loss of contact between the polymer rich matrix and the rotating cone of the viscometer. Upon storage below the cloud point temperature the demixed polymer solution displays synereses; DIDP is expelled out of the continuous phase.
How is shear stress related to viscosity in viscometry?
According to Newton’s Law [3], shear stress is viscosity times shear rate. Therefore, the viscosity (eta) is shear stress divided by shear rate. Only Newtonian liquids can be described by this simple relation. Equation 3: Newton’s Law reformulated: Dynamic viscosity is shear stress divided by shear rate.
How is the viscosity of a dilute solution determined?
Dilute Solution Viscometry (DSV) is a testing method used to determine the relative, inherent, or intrinsic viscosity of a polymer. Viscosity increases or decreases as molecular weight increases or decreases.
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