ISO 3251:2019

Overview - ISO 3251:2019 (Determination of non‑volatile‑matter)

ISO 3251:2019 specifies a laboratory method to determine the non‑volatile‑matter content by mass of paints, varnishes, binders, polymer dispersions and certain condensation resins. The standard defines sampling, apparatus, procedure (weighing, heating, cooling), expression of results and precision requirements. It is primarily a comparative test method: results depend on heating temperature and time and therefore give relative, not absolute, non‑volatile‑matter values.

Key topics and technical requirements

• Scope: Applies to paints, varnishes, binders, polymer dispersions, rubber lattices (with appropriate heating), and formulated dispersions containing pigments, fillers and auxiliaries.
• Apparatus: flat‑bottom dishes (typical base Ø 75 mm), controlled air oven with forced ventilation (temperature control ±2 °C up to 150 °C), analytical balance (0.0001 g), desiccator with desiccant (e.g. silica gel orange).
• Sampling and preparation: Follow ISO 15528 (paints) and ISO 123 (polymer dispersions/rubber latex); prepare samples per ISO 1513.
• Procedure: Perform duplicate determinations. Weigh empty dish (m0), dish + test portion (m1), heat at specified temperature/time, cool in desiccator, weigh dish + residue (m2).
• Calculation: Non‑volatile matter NV (%) = (m1 − m2) / (m1 − m0) × 100.
• Test parameters to specify: test temperature, heating period and test portion mass (common parameters are listed in Annex A).
• Precision and repeatability: Clause 9 gives repeatability (r) and reproducibility (R) data; duplicates should agree within specified limits (e.g., ±2 % absolute for paints/varnishes).
• Limitations & cautions: Results vary with heating conditions due to solvent retention, thermal decomposition and evaporation of low‑molecular‑mass constituents. Infrared or microwave drying is not standardized because some polymers decompose under those treatments.

Practical applications and users

• Quality control in paint and coatings manufacturing to compare production batches.
• R&D and formulation labs measuring solids content of polymer dispersions, varnishes and resins.
• Raw material inspection for suppliers of binders, pigments and fillers.
• Regulatory or contractual testing where agreed test parameters provide consistent comparative data.
• Useful for assessing solids content prior to film‑forming, drying calculations and estimating coverage.

Related standards

• ISO 4618 - Terms and definitions for paints and varnishes
• ISO 15528 - Sampling for paints and varnishes
• ISO 1513 - Sample preparation for paints and varnishes
• ISO 123 / ISO 124 - Sampling and solids determination for latex/rubber lattices
• ISO 3233 - Methods to determine volume of non‑volatile matter

Keywords: ISO 3251:2019, non‑volatile‑matter, paints varnishes plastics, solids content determination, polymer dispersions, coating quality control.