Overview
ISO 17710:2023 - Plastics - Polyols for use in the production of polyurethanes - Determination of degree of unsaturation by microtitration - defines a microtitration test method for measuring the degree of unsaturation in polyether polyols used to make polyurethanes. The method is based on the reaction of mercuric acetate with carbon–carbon double bonds and quantifies the acetic acid released by potentiometric titration with methanolic KOH. This second-edition standard adapts the chemistry of existing methods (e.g., ASTM D4671) into a microtitration procedure that uses smaller reagent volumes and reduces mercury waste.
Key topics and requirements
- Principle: Unsaturated sites react with methanolic mercuric acetate to form acetoxymercuric products and acetic acid; released acid is titrated potentiometrically with 0.05 mol/L methanolic KOH. Sodium bromide is added to convert excess mercuric acetate to non-interfering mercuric bromide prior to titration.
- Scope limits: Excludes unsaturation conjugated with carbonyl, carboxyl or nitrile groups.
- Reagents & concentrations: Typical reagents include 0.05 mol/L methanolic mercuric acetate, 0.05 mol/L methanolic KOH, 0.05 mol/L methanolic HCl, NaBr and methanol. Water quality per ISO 3696.
- Apparatus: Autotitrator with appropriate electrodes, analytical balance (0.1 mg), 2 mL pipette (ISO 4787), and 50–100 mL titration vessel.
- Sampling & preparation: Samples must be dry, free of inorganic halides, handled in dry borosilicate glassware, and protected from CO2. Test portion sizing is controlled so ≤ 0.033 meq unsaturation per gram in the portion.
- Calculations & corrections: Results are reported in meq/g and corrected for sample acidity or basicity (separate titrations without mercuric reagent). Blank titration is required.
- Precision & bias: The standard provides repeatability and reproducibility criteria (interlaboratory data and r/R limits) to judge acceptability.
Applications and users
ISO 17710:2023 is suited for:
- Quality control and specification testing of polyether polyols used in flexible and rigid polyurethane foams, elastomers and coatings.
- R&D labs monitoring side reactions (unsaturated chain ends) that affect functionality and molecular-weight distribution.
- Contract testing laboratories performing standardized unsaturation analysis for manufacturers and formulators.
Primary users: polymer chemists, QC analysts, materials laboratories, and manufacturers of polyurethanes.
Related standards
- ASTM D4671 (methodal chemistry basis)
- JIS K 1557 (related polyol testing)
- ISO 3696 (laboratory water), ISO 4787 (volumetric glassware), ISO 6353 series (reagent specifications)
Note: The method uses mercury-containing reagents; follow all safety, handling and hazardous-waste regulations when implementing ISO 17710:2023.
Open preview (PDF)Plastics — Polyols for use in the production of polyurethanes — Determination of degree of unsaturation by microtitration