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"I have purchased 7 GPC systems from Viscotek in Europe, US and Canada. I am very satisfied. The systems are robust and affordable. OmniSEC software is very user friendly and highly versatile."
- R.N., Academic Institution
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Application Notes
Our database of GPC/SEC application notes explain the use of concentration, viscometer and light scattering detectors to obtain a distribution of absolute molecular weight, size and intrinsic viscosity, as well as information on conformation, aggregation, branching and copolymer composition.
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"The service provided by Viscotek representatives is unmatched by any other in the industry... A wonderful addition to the polymer community."
- E.F, Ph.D., Academic Institution
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Tetra Detector Array
A revolutionary, integrated multiple-detector device designed for the characterization of natural and synthetic polymers and copolymers, proteins, protein conjugates, excipients and other macromolecules. Comprised of modular Refractive Index, Ultra-Violet, Low Angle Light Scattering and Viscometer detectors. |
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Dilute Solution Viscosity Theory - Calculations |
The viscosity of the polymer solution is measured relative to the viscosity of the
pure solvent.
Where η is the viscosity of the solution and η0 is the viscosity
of the pure solvent.
Derived Functions of RV
The most common function of Relative Viscosity is called the inherent viscosity.
The concentration c must be known exactly or the results will not correlate with
Mw. A less common function of RV is the intrinsic viscosity, which is defined as
the inherent viscosity in the limit of infinite dilution.
Typically, solutions of various concentrations are analyzed and the function is
plotted vs. concentration. The intercept (c = 0) is equal to the intrinsic viscosity.
Intrinsic Viscosity
It is not viscosity!
- Note, the units are in dl/g.
- Viscosity is measured in Pa.s or centipoise.
It is the volume per unit mass that the polymer occupies
in a solution.
- Inverse of molecular density.
It is directly related to molecular weight by the Mark-Houwink
equation:
[η] = intrinsic viscosity.
k = Mark-Houwink constant.
a = Mark-Houwink constant relating to structure.
0 to 0.1 = sphere, 0.35 to 0.80 = random coil, and 1.5 to 2
= rigid rod structure.
Mv = Viscosity average molecular weight.
Nomenclature for Solution Viscosity
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RESULT |
UNITS |
EQUATION |
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Relative Viscosity |
dimensionless |
ηr = η/η0 |
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Specific Viscosity |
dimensionless |
ηsp = ηr
- 1 = (η- η0)/η0 |
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Inherent Viscosity |
dl/g |
ηinh = (ln ηr)/c |
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Reduced Viscosity |
dl/g |
ηred = ηsp/c |
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Intrinsic Viscosity |
dl/g |
[η] = (ηsp/c)|c→0 |
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Absolute Viscosity |
cP |
η = ηr x ηsolvent |
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Kinematic Viscosity |
cS |
ηk = η / density |
Where η0 = Solvent Viscosity and η
= Solution Viscosity
Capillary Viscometer Principle
The Relative Viscometer measures the solvent and sample viscosity simultaneously,
avoiding errors due to temperature fluctuation and solvent variations.
Poiseulle’s Law:
For the two capillaries in series the pressure ratio will be:
Under baseline conditions, pure solvent flows through both R1 and R2. At baseline,
h in both capillaries are equal and cancel. Since the capillaries are in series
and liquid is non-compressible, the flow rates Q1 and Q2 are also equal and cancel.
So this leaves:
Where k is the instrument constant.
After sample injection into the sample loop, the solvent is diverted from the sample
loop by-pass route, and enters the sample loop to push sample across capillary 2,
at which time the pressure on transducer will reach a maximum or plateau. |
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