Overview
ISO 1628-4:1999 specifies a standardized method for determining the viscosity number (VN) and relative viscosity of polycarbonate (PC) moulding and extrusion materials in dilute solution using capillary viscometers. The procedure covers pure polycarbonates, blends with other polymers and mixtures, with or without fillers, and defines required test conditions, sample preparation, measurement and calculation methods. Key outcome units include viscosity number expressed in ml·g⁻¹ and dimensionless relative viscosity.
Key topics and technical requirements
- Test concentration and solvent: Polycarbonate solutions are prepared at 5 g·l⁻¹ using dichloromethane (analytical grade) or equivalent.
- Measurement temperature: All measurements are made at 25 °C ± 0.1 °C in a thermostatic bath.
- Viscometer specification: Preferred apparatus is an Ubbelohde capillary viscometer (size 0C, 0.36 mm capillary, 2 ml receiver) per ISO 3105; other validated viscometers or automatic devices may be used if equivalent results are obtained.
- Timing and accuracy: Timing devices must meet specified resolution and accuracy (e.g., read to 0.1 s and accurate to –0.1 %; higher precision for automatic systems). Solvent efflux times must be repeatable within 0.2 %.
- Kinetic-energy correction: The standard requires consideration of the Dt kinetic-energy correction for efflux time; inclusion is necessary for accurate VN with specified capillaries.
- Sample handling: Procedures for non-reinforced, pigmented, or glass-fibre‑reinforced materials are given - including filtration, use of filter aid or centrifugation, evaporation and re-dissolution of the polymer film; drying oven set at 110 °C.
- Calibration and validation: Annex A details instrument calibration and verification using reference liquids and certified polycarbonate standards; acceptable deviation vs. reference is specified (≤ 0.4 %).
Practical applications
- Quality control and specification of PC resins for injection moulding and extrusion.
- Raw‑material verification for polymer producers, compounders and converters.
- Supporting product compliance, batch-to-batch consistency checks and formulation development where molecular weight proxies (via VN) are used.
- Research labs assessing effects of additives, blending or recycling on polymer chain length/viscosity.
Who should use this standard
- Polymer testing laboratories and quality-control teams
- Polycarbonate manufacturers and compounders
- Material certifiers and standards bodies
- R&D teams working on PC formulations or processing conditions
Related standards
- ISO 1628-1:1998 - General principles for dilute-solution viscometry
- ISO 1628 (other parts) - Methods for PVC, PE/PP, polyesters, PMMA
- ISO 3105 - Glass capillary viscometer specifications
- ISO 7391-1 / -2 - Polycarbonate designation and test specimen preparation
Keywords: ISO 1628-4, viscosity number, VN, polycarbonate viscosity, capillary viscometer, Ubbelohde, dichloromethane, relative viscosity, polymer testing.