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Viscosity Number - ISO 307

The viscosity number provides a measure of the molecular mass of a polymer. ISO 307 deals with the determination of viscosity number for polyamide materials.

The polyamide material is dissolved in a solvent and the solution is poured into a viscometer. The viscometer is immersed in a constant temperature bath at 25°C. The time for the solution to flow between the two graduation lines is recorded. The test is repeated with the solvent and the time is recorded.

Name Chemical Symbol Concentration
Formic Acid HCOOH 90%
m-Cresol C7H8O 99%
Sulfuric Acid H2SO4 96%

Viscosity number is calculated using:
VN = (t/to - 1)/c
where t is the flow time of the solution in seconds,
to is the flow time of the solvent in seconds,
and c is the concentration of the polymer in g/ml of solution.

Ubbelohde Viscometer