Overview
ISO 585:1990 defines a gravimetric method for the determination of moisture content in unplasticized cellulose acetate. The method is intended for materials with moisture content not exceeding 10% and is commonly used to obtain the dry mass required for analytical methods and quality control.
The principle is simple and robust: a test portion is dried in a thermostatic oven at 105 °C, then weighed. The moisture content is calculated from the loss of mass.
Key Topics
- Scope: Applies only to unplasticized cellulose acetate having moisture ≤ 10%.
- Principle: Drying at 105 °C and mass loss measurement to determine moisture content.
- Apparatus: glass weighing bottle with ground-glass lid, desiccator with anhydrous calcium chloride, oven capable of 105 °C ± 2 °C, balance accurate to 1 mg.
- Sample size and handling: approximately 5 g test portion weighed to 1 mg precision in a pre-dried weighing bottle.
- Drying conditions: test portion (lid removed) placed in oven at 105 °C ± 2 °C for 3 hours, then cooled in a desiccator and reweighed to nearest 1 mg.
- Repeatability: Carry out two determinations. If difference between the two moisture percentages > 0.1%, repeat the test. Take the mean of two acceptable determinations.
- Calculation: Moisture content (%) = (m1 - m2) / m1 × 100, where m1 is mass before drying and m2 after drying.
- Precision: Interlaboratory precision data are not available; the method's precision is therefore not established for disputed results or formal specifications.
Applications
This standard is primarily applied where accurate knowledge of dry mass is required, including:
- Preparation and interpretation of analytical test results that depend on dry-mass basis.
- Quality control of unplasticized cellulose acetate raw materials and intermediate products.
- Routine laboratory moisture checks to verify storage and handling conditions.
Practical benefits include a straightforward procedure requiring standard laboratory equipment and clear acceptance criteria for repeatability between determinations.
Related Standards
- Look for other ISO methods describing moisture determination for different plastics or for plasticized grades; applicability and drying conditions can differ.
- Consult laboratory and safety standards for handling heated ovens, desiccants, and combustible fines; the standard includes a general safety warning.
Note: Follow the test report requirements specified by ISO 585:1990 - include reference to the standard, full product identification (physical form), and the percentage moisture content determined. The method is a minor revision of the original 1982 edition and cancels that edition.
