Overview
ISO 1599:1990 - "Plastics - Cellulose acetate - Determination of viscosity loss on moulding" specifies a laboratory method to quantify the reduction in viscosity (viscosity loss) that occurs when cellulose acetate is moulded. The standard applies to cellulose acetate without additives or fillers and with an acetic acid yield above 50%. The test uses dimethyl phthalate as a plasticizer, controlled moulding conditions, and viscosity measurements referenced to ISO 1157 to calculate percentage viscosity loss after moulding.
Key topics and requirements
- Scope and suitability: For neat cellulose acetate (no interfering additives/fillers) and acetic acid yield >50%.
- Sample preparation: Two permitted methods for incorporating dimethyl phthalate; powder must pass a 710 µm sieve if required. Moisture content must be <0.5% (ISO 585 moisture determination referenced).
- Moulding conditions:
- Mould pre-heated to 200 °C ±2 °C.
- Hydraulic press capable of ≥8 MN/m² contact pressure.
- Contact pressure 2 min, then full pressure for 10 min for 1.5 mm thickness (add 0.5 min per additional 0.5 mm up to 5 mm).
- Cooling until rigid (mould temperature 2 min after start of cooling at least 30 °C below moulding temperature).
- Post-mould handling: Grind moulding to <0.9 mm particle size, dry at 70 °C ±2 °C for 2 h; prepare solutions in dichloromethane/methanol per ISO 1157.
- Viscosity measurement and calculation:
- Determine viscosity ratio of original and moulded material according to ISO 1157.
- Compute percentage viscosity loss from the measured viscosity ratios.
- Two complete determinations required; perform additional tests if results differ by >10% of the mean.
- Apparatus and reagents: Hydraulic press, specified mould (1.5–5 mm), grinder, oven, viscometer per ISO 1157, dimethyl phthalate (analytical grade), propan-2-ol and solvent mixture. Safety warnings for flammable and hazardous solvents are noted.
- Precision: Inter-laboratory precision data are not available; the method may be unsuitable for contractual disputes until such data exist.
Applications and users
ISO 1599 is primarily used in:
- Materials R&D to assess polymer degradation during processing.
- Quality control in cellulose acetate production and compound formulation.
- Molders and converters evaluating processing settings (temperature, pressure, time) on polymer integrity.
- Test laboratories, certification bodies, and specification writers who require a standardized method to measure processing-induced depolymerization (viscosity loss).
Keywords: ISO 1599:1990, cellulose acetate viscosity, viscosity loss on moulding, dimethyl phthalate, ISO 1157.
Related standards
- ISO 1157 - Plastics - Cellulose acetate in dilute solution - Determination of viscosity number and viscosity ratio (reference method for viscosity measurements).
- ISO 585 - Plastics - Unplasticized cellulose acetate - Determination of moisture content.
- ISO 565 - Test sieves (mesh specification for sample preparation).