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The viscosity of Walsroder Nitrocellulose and Walsroder NC-Chips is determined exclusively by the Cochius method for grading purposes. To test the viscosity, dried nitrocellulose is dissolved in a solvent mixture in concentrations appropriate to the viscosity category. In a 7 mm Cochius tube (temperature controllable vertical glass tube with a diameter of 7 mm) at 18°C the time required for a rising air bubble of around 0.5 to 2.0 cm3 to cover the distance of 500 mm between two marks indicated on the viscometer is measured in seconds.
The Cochius viscosity of the individual grades is measured in the following solvent mixtures:
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| A grades: | butanol : ethyl acetate : toluene : ethanol = 1 : 2 : 3 : 4 |
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| AM grades: | butyl acetate (98/100) or butanol : ethyl acetate : toluene : ethanol = 1 : 2 : 3 : 4 |
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| E grades: | butanol : butyl acetate (98/100) : toluene = 3 : 4 : 5 |
Approximate viscosity values in absolute units (mPa s) are calculated by multiplying the Cochius seconds by a factor of 3.65.
The viscosities and the solvent mixtures used and the concentration of the individual grades of Walsroder Nitrocellulose and Walsroder NC-Chips are shown in the Product Range.
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