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ISO 307 Test Standard Explained

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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.

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

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

Ubbelohde Viscometer

Property information for specific grades of resin are available in the Prospector Plastics Database.