Overview
ISO 11909:2025 - "Binders for paints and varnishes - Polyisocyanate resins - General methods of test" specifies general test methods for polyisocyanate resins and their solutions when used as binders in paints, varnishes and related products. This third edition updates the 2007 version and standardizes laboratory procedures for properties such as colour, viscosity, non‑volatile matter, flash point, density and isocyanate (NCO) content. The document includes a normative Annex A that details the quantitative determination of isocyanate groups.
Key topics and requirements
- Scope and sampling: Applies to polyisocyanate resins (free or blocked isocyanate groups). Representative sampling is done per ISO 15528.
- Core test methods: Table of required methods references established ISO tests:
- Isocyanate (NCO) determination (Annex A): Principle uses excess dibutylamine (CAS 109‑89‑7) reacted with resin, with back‑titration by hydrochloric acid (CAS 7647‑01‑0). Indicator titration (bromophenol blue) or potentiometric titration is permitted; potentiometry is introduced as a general alternative for highly coloured resins. Reagents also include toluene (CAS 108‑88‑3) and ethanol.
- Test conditions for non‑volatile matter: Example heating/time settings include HDI biuret 1 h at 80 °C, HDI cyanurate 1 h at 105 °C, TDI/MDI adducts 1 h at 125 °C, IPDI polyisocyanates 1 h at 150 °C.
- Precision and reporting: Annex A provides repeatability/reproducibility figures for typical products and specifies test report elements (identification, methods used, results, deviations, anomalies, date).
Applications and users
ISO 11909:2025 is used by:
- Paint, varnish and coatings manufacturers for incoming raw‑material QC and product specifications
- Analytical and contract test laboratories performing NCO content and physical property testing
- R&D and formulation chemists assessing binder reactivity, solids content and rheology
- Regulatory and compliance teams documenting test procedures for safety and transport classification
Practical uses include quality control of polyisocyanate binders, verifying NCO content (which affects curing and handling), setting specification limits for viscosity/solids, and ensuring consistent production and product safety.
Related standards
- ISO 10283 - Determination of monomeric diisocyanates
- ISO 3251 - Non‑volatile matter determination
- ISO 3219 - Rheology methods
- ISO 2811 series - Density determination
- ISO 15528 - Sampling of paints and varnishes
Keywords: ISO 11909:2025, polyisocyanate resins, binders for paints and varnishes, NCO content, isocyanate determination, titration, potentiometric titration, non‑volatile matter, viscosity testing.
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