Overview
ISO 4575:2007 specifies a laboratory method for determining the apparent viscosity of poly(vinyl chloride) (PVC) pastes at high shear using the Severs rheometer. The standard applies particularly to “standard pastes” prepared according to ISO 4612 (planetary-mixer method) or ISO 11468 (dissolver method). The procedure measures paste flow through a calibrated die under controlled pressure and temperature to derive shear rate and apparent viscosity values useful for quality control and material characterization.
Key topics and technical requirements
- Scope and principle: Measures apparent viscosity of PVC pastes by forcing paste through a die in a Severs rheometer and calculating shear rate and viscosity from measured flow rates and applied pressures.
- Apparatus: Severs rheometer (capacity 500–1 000 ml) with temperature jacket, non-deformable dies (Die A / Die B), optional piston, pressurizing device (nitrogen), timer, balance and thermometer.
- Dies (specified dimensions): Die A and Die B have a tube radius of 1.5 ± 0.05 mm; heights are 45 ± 0.5 mm (Die A) and 22.5 ± 0.5 mm (Die B).
- Test conditions: Jacket temperature maintained at (23 ± 0.5) °C; select at least four test pressures from preferred values (100, 160, 250, 400, 630, 1 000, 1 600, 2 500 kPa). Begin with Die A at 2 500 kPa to choose appropriate die based on shear rate.
- Procedure: Introduce paste, condition to temperature, apply regulated pressure, collect flow into weighed beakers, record times, calculate mean flow rate.
- Calculations: Formulæ for flow rate, shear rate and apparent viscosity are provided (noting the practical use of Newtonian-based formulae for PVC pastes). Annex A contains exact formulae for non-Newtonian fluids.
- Reporting: Include test reference, paste identification and formula, preparation method, paste density, die used, conditioning time, tabulated apparent viscosity vs. shear rate, and optional graph.
Applications and who uses it
- Quality control: PVC compounders and converters use ISO 4575 to monitor paste viscosity for consistent processing (calendering, extrusion).
- R&D and formulation: Materials scientists and formulators evaluate effects of plasticizers and polymer grades on high-shear behavior.
- Acceptance testing and specifications: Test laboratories and standards bodies use the method to verify compliance with product specifications that reference apparent viscosity.
- Troubleshooting processing: Engineers apply measured viscosity vs. shear-rate data to predict manufacturing performance under high shear.
Related standards
- ISO 4612 - Preparation of PVC pastes (planetary-mixer method)
- ISO 11468 - Preparation of PVC pastes (dissolver method)
Keywords: ISO 4575, Severs rheometer, PVC paste apparent viscosity, shear rate, high-shear viscosity, dielectric die, plasticizer testing.
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