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.
Solvents
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