ISO 1183-2:2019

Overview

ISO 1183-2:2019 specifies the density gradient column method for determining the density of non-cellular, void‑free moulded or extruded plastics and pellets. The standard describes use of a vertical column filled with a continuous density gradient (mixture of two miscible liquids) in which test specimens settle to the level matching their density. Density is an important tracer of composition, physical structure and uniformity in polymer materials.

Key topics and requirements

• Scope: Applicable to non‑cellular plastics (moulded, extruded or pellet forms) in void‑free condition.
• Apparatus:
  • Density gradient column (typical diameter ≥ 40 mm) with a readable scale (1 mm graduation is normal).
  • Thermostatically controlled liquid bath (temperature control to ±0.1 °C or ±0.5 °C depending on required sensitivity).
  • Calibrated glass floats (approximately spherical, ≤ 5 mm diameter) spanning the measurement range.
  • High‑precision balance (≈ ±0.1 mg) and filling devices (siphon/pipette).
• Immersion liquids: Two miscible liquids of different densities are mixed to form the gradient. Annex A lists example systems (e.g., methanol/benzyl alcohol, isopropanol/water, water/sodium bromide, ethanol/zinc chloride). Some liquids can be hazardous - observe safety precautions.
• Specimen preparation: Pieces should be smooth, free from cavities and sized to allow accurate location of the specimen centre. Thin films (< 0.05 mm) require longer equilibration (≥ 1.5 h).
• Procedure:
  • Calibrate glass floats by matching them to known-density mixtures and determining float density to 0.0001 g/ml (pycnometer or equivalent).
  • Prepare and stabilize the density gradient in the column (see Annex B for example methods).
  • Place wetted specimens in the column, allow equilibrium (typically ≥ 10 min; longer for thin films).
  • Read specimen level and determine density either graphically (float density vs height plot) or by interpolation; use higher‑order fits if the relationship is non‑linear.
• Reporting: Test report must reference ISO 1183-2:2019 and include material ID, specimen prep, immersion liquids, densities for three specimens plus mean, test temperature, buoyancy corrections (if applied) and date.

Applications and users

• Practical uses: material quality control, incoming inspection of pellets, process monitoring for extrusion/moulding, R&D for polymer formulation, assessing batch uniformity and detecting compositional changes.
• Typical users: polymer testing laboratories, QC/QA engineers, materials scientists, suppliers and purchasers of plastics, and standards bodies implementing material specifications.

Related standards

• ISO 1183-1 - density by immersion/pycnometer/titration methods (complements Part 2)
• ISO 291 - standard atmospheres for conditioning and testing

Keywords: ISO 1183-2:2019, density gradient column, plastics density determination, non-cellular plastics, calibrated glass floats, immersion liquids, polymer quality control.