Overview
ISO 307:2019 - "Plastics - Polyamides - Determination of viscosity number" specifies a laboratory method to determine the viscosity number of dilute solutions of polyamides. The procedure measures flow times of a solvent and a polymer solution (typically at 25 °C and 0.005 g/ml concentration) in a capillary viscometer and calculates the viscosity number according to the general principles in ISO 1628‑1. The standard applies to a wide range of polyamides (PA 46, PA 6, PA 66, PA 69, PA 610, PA 612, PA 11, PA 12, PA MXD6 and various copolyamides and blends) that are soluble in the specified solvents. It excludes polyamides produced by anionic polymerization of lactams or those cross‑linked (normally insoluble).
Key technical topics and requirements
- Scope of applicability: Lists specific polyamide types (see ISO 16396‑1 for designations). Solubility in the specified solvents is a prerequisite.
- Principle: Measure solvent and solution flow times in the same capillary viscometer; compute viscosity number using ISO 1628‑1 formula.
- Solvents and concentrations: Includes strict solvent concentration requirements such as sulfuric acid 96.00% ±0.20% and formic acid 90.00% ±0.15%; solvent concentration must be checked regularly (e.g., every 2 weeks).
- Viscometers and kinetic correction: Recommends specific Ubbelohde‑type viscometers (ISO 3105). Apply the Hagenbach (kinetic energy) correction when flow times are below manufacturer thresholds (noted for Ubbelohde types).
- Sample preparation: Test samples must be completely soluble; insoluble additives like glass/carbon fibres should be removed. Extractables (e.g., caprolactam) are considered part of the sample mass.
- Interference and conversion limits: Additives can increase or decrease viscosity number depending on solvent; when additives interfere, viscosity numbers are only suitable for intra‑product comparison and cannot reliably be converted between solvents.
- Supporting procedures: Annexes provide titration/flow‑time/density methods to adjust and verify solvent concentrations.
Practical applications and users
- Applications
- Quality control and production monitoring of polyamide batches
- Comparative testing for product development and formulation optimization
- Material verification for incoming inspection and supplier qualification
- Research and polymer characterization (molecular mass trend indicator)
- Who uses it
- Polymer testing laboratories and QC teams
- Materials engineers, compounders and formulators
- Certification and compliance bodies
- R&D groups working on polyamide grades and blends
Related standards
- ISO 1628‑1 - General principles for viscosity determination of polymers in dilute solution
- ISO 3105 - Glass capillary kinematic viscometers (specifications and operation)
- ISO 16396‑1 - Polyamide designation system
- ISO 3451‑4 and ISO 15512 - Complementary tests (ash, water content)
Keywords: ISO 307:2019, viscosity number, polyamides, viscosity measurement, Ubbelohde viscometer, sulfuric acid 96%, formic acid 90%, polymer quality control, ISO standards.
