Overview
ISO 14446:1999 specifies a standardized procedure for determining the viscosity of industrial cellulose nitrate (nitrocellulose) solutions and for classifying those solutions. The standard covers cellulose nitrate grades with nitrogen contents typically between 10.7 % and 12.6 % by mass and establishes a repeatable test route that reduces variability caused by differing solvents and test techniques.
Key elements of the method include dissolution in an acetone/water solvent (95 % acetone / 5 % water), density measurement by pyknometer or equivalent, and viscosity measurement using a Höppler falling-ball viscometer (see ISO 12058-1). The method targets a reference dynamic viscosity of (400 ± 25) mPa·s for classification purposes.
Safety note: cellulose nitrate is flammable and hygroscopic. Samples should be kept moistened and handled per the standard’s safety guidance.
Key Topics
- Scope and purpose: Standardized viscosity determination for industrial nitrocellulose used in binders for paints and varnishes.
- Test principle: Dissolve dried nitrocellulose in the specified acetone/water mix, measure density and falling-ball time at controlled temperature (20 ± 0.1 °C), compute dynamic viscosity.
- Apparatus & conditions:
- Höppler falling-ball viscometer (ball No. 4)
- Thermostat for 20 ± 0.1 °C
- Pyknometer or plummet for density
- Oven for drying at about 65 °C
- Classification: Annex A defines a type code combining solution concentration (that yields the reference viscosity) and a solvent/solubility letter: E (ester-soluble), M (medium-soluble), A (alcohol-soluble). Example: 24E denotes a 24 % solution that yields ~400 mPa·s and is ester-soluble.
- Precision: the method references ISO 12058-1 precision data (repeatability and reproducibility figures).
Applications
- Quality control of nitrocellulose raw materials used in paints, varnishes, printing inks and coatings.
- Supplier and purchaser specification: defining "standard types" to avoid classification differences caused by different solvents or viscosity methods.
- Formulation guidance: selecting the appropriate nitrocellulose grade (A, M, E) and concentration to achieve target rheology in coatings and inks.
Related Standards
- ISO 12058-1 - falling-ball viscometer method (referenced for viscometer constant and procedure)
- ISO 760 - Karl Fischer method for water content
- ISO 2811 (parts 1–3) - density determination methods (pyknometer, plummet, oscillator)
- ISO 15528 - sampling of paints and varnishes
By following ISO 14446:1999, laboratories and manufacturers achieve consistent, comparable viscosity data and a harmonized classification scheme for nitrocellulose solutions used in coating and ink industries.