Overview
EN ISO 1598:1999 (identical to ISO 1598:1990) specifies a laboratory test method for determining insoluble and visible particles in cellulose acetate. It covers preparation, dissolution and visual counting of particles (including contaminants and foreign matter) that are insoluble in a defined solvent mixture and have a projected diameter ≥ 0.15 mm. The method is intended for cellulose acetate with an acetic acid yield above 50 % and without additives that affect results.
Key topics and requirements
- Scope and applicability: Designed for cellulose acetate powders (passed 710 μm sieve) used in quality control and raw-material inspection.
- Sample preparation:
- Use a test portion equivalent to 20 g of dry cellulose acetate (corrected for moisture per ISO 585).
- Spread sample in a transparent glass dish with a ruled grid of 25 mm square cells.
- Reagents and solvent system:
- Solvent mixture prepared from dichloromethane and methanol (90:10 by volume), mixed with dimethylphthalate in a 3:1 (mixture:phthalate) volume ratio; solvents must be particle-free.
- Apparatus and reference:
- Illuminated viewing stand with opal glass for even backlighting.
- Standard reference particle: opaque circular spot 0.15 mm ± 5 μm used to compare apparent particle area.
- Counting procedure:
- After dissolution, examine the dish square-by-square and count visible particles whose projected area equals or exceeds the reference particle.
- Include all visible particle types irrespective of color or opacity.
- Perform two complete determinations and report the mean.
- Result expression:
- Insoluble-particle content expressed as number of particles per 100 g dry cellulose acetate (formula using counted particles and test portion mass is defined in the standard).
- Limitations and precision:
- Precision (inter-laboratory reproducibility) is not provided; caution is advised before using this method in contractual disputes.
- Safety:
- Solvents used (dichloromethane, methanol) are hazardous-follow appropriate health, safety and ventilation practices.
Applications and users
- Quality control and acceptance testing for cellulose acetate producers and converters.
- Incoming raw-material inspection for plastics processors and compounders.
- Analytical and materials testing laboratories performing contamination or cleanliness evaluations.
- R&D teams assessing process cleanliness and filtration effectiveness in cellulose acetate manufacture.
Related standards
- ISO 565 - Test sieves (nominal opening sizes) - relevant for sample sieving.
- ISO 585 - Determination of moisture content for unplasticized cellulose acetate (used to calculate dry-mass test portions).
Keywords: EN ISO 1598:1999, ISO 1598, cellulose acetate, insoluble particles, particle counting, dichloromethane, dimethylphthalate, methanol, plastics standard, quality control.