ISO 1628-6:1990

Overview

ISO 1628-6:1990 specifies test conditions for determining the viscosity number (I.V.) and limiting (intrinsic) viscosity of methyl methacrylate polymers (PMMA). It covers homopolymers, copolymers and blends containing at least 80% methyl methacrylate (MMA) by mass, intended for molding and extrusion. The standard defines required apparatus, solvent, concentrations, temperature control and calculation approach (including Hagenbach kinetic-energy corrections) for accurate viscosity-number determination.

Key topics and technical requirements

• Scope: PMMA homopolymers and copolymers (≥80% MMA) with or without additives as per ISO 8257-1.
• Solvent: Analytical-grade chloroform, stabilized with <1% ethanol, stored in a dark bottle.
• Solution concentration: 2.6 g polymer per litre (example prep: 0.26 g ±0.005 g in 100 mL flask).
• Viscometers: Ubbelohde capillary viscometers are specified as reference:
  • Type OC: capillary dia. 0.36 mm, reservoir 2 mL.
  • Type Ml (micro): capillary dia. 0.40 mm, reservoir 0.75 mL.
  • Other ISO 3105 viscometers may be used if equivalent results are demonstrated.
• Temperature control: 25 °C ± 0.05 °C bath for measurements.
• Measurement procedure: introduce solvent/solution through a fritted glass funnel (max pore 40 µm, class P40 per ISO 4793), perform 3–5 flow-time determinations for solvent and solution; repeat if variation exceeds thresholds (0.2 s for OC, 0.03 s for Ml).
• Calculations: viscosity number is calculated from measured flow times, solvent viscosity and density, polymer concentration and includes kinetic-energy (Hagenbach) corrections as described in ISO 1628-1 and annex A of this part.
• Calibration: Annex A recommends calibrating the viscometer using standard liquids (examples given: n-undecane, dichloromethane, trichloroethylene, tetrachloroethylene) and provides kinematic viscosity and density reference values for these standards.
• Intrinsic viscosity: Annex B outlines how to estimate intrinsic viscosity [η] from a single-concentration measurement using the provided relation.

Applications and who uses it

• Quality control and acceptance testing for PMMA resins used in injection molding and extrusion.
• Material characterization in R&D when comparing molecular weight-related properties (viscosity correlates with molecular weight).
• Raw-material suppliers and compounders validating batches against product specifications.
• Testing and certification laboratories requiring a standardized method for viscosity number and intrinsic viscosity measurement of MMA-based polymers.
• Useful for formulation engineers, polymer chemists and regulatory/compliance teams.

Related standards

• ISO 1628-1 - General principles for viscosity-number methods
• ISO 3105 - Glass capillary viscometers specifications
• ISO 8257-1 - PMMA designation for molding and extrusion
• ISO 4793 - Laboratory fritted filters (porosity classification)

Keywords: ISO 1628-6, PMMA, methyl methacrylate polymers, viscosity number, intrinsic viscosity, Ubbelohde viscometer, chloroform solvent, polymer testing, plastics characterization.