Overview
ISO 2114:2000 specifies standardized laboratory methods to determine the partial acid value (PAV) and total acid value (TAV) of polyester resins and binders for paints and varnishes. The methods provide reproducible titrimetric procedures (potentiometric or colorimetric) to quantify milligrams of KOH required to neutralize acidic groups in a resin sample. ISO 2114 is intended for quality control, acceptance testing and monitoring of polycondensation reactions; it is not applicable to phenolic resins.
Key topics and technical requirements
- Two methods:
- Method A (Partial acid value) - dissolves a weighed resin portion in a toluene/ethanol solvent mixture and titrates (potentiometrically recommended) with standard KOH in ethanol or methanol to determine acid groups excluding hydrolyzable anhydrides.
- Method B (Total acid value) - dissolves resin in a pyridine / methyl ethyl ketone / water solvent, allows hydrolysis of anhydrides (20 min), then titrates to determine all carboxyl and hydrolysed anhydride acidities.
- Titrant and reagents:
- Standard 0.1 mol/L KOH in ethanol or methanol (check concentration before use; 0.5 mol/L recommended if >25 mL titrant expected).
- Solvent compositions and purity limits are specified (e.g., anhydrous ethanol, toluene, pyridine - note pyridine is toxic and requires ventilation and PPE).
- Optional color indicators: phenolphthalein and bromothymol blue; potentiometric end-point detection is preferred.
- Apparatus and procedure:
- Analytical balance (±1 mg), burette, magnetic stirrer, potentiometric titration system with suitable electrodes.
- Duplicate determinations; blank corrections; sample mass chosen according to expected acid value (guidance provided).
- Results and calculations:
- Results expressed as mg KOH per g of resin (PAV or TAV).
- Option to report values for the solid resin using non-volatile-matter correction per ISO 3251.
- Reporting rules include repeat criteria (e.g., replicate agreement thresholds).
Applications and users
- Primary users:
- Quality-control laboratories in paint, varnish and resin manufacturing
- R&D teams monitoring polycondensation or resin synthesis
- Third-party testing and certification bodies
- Practical uses:
- Acceptance testing against product specifications
- Monitoring reaction completion and free acid/anhydride content
- Ensuring batch-to-batch consistency and regulatory compliance
Related standards
- ISO 3251 - determination of non-volatile matter (used for reporting acid values on solid resin)
- ISO 3696 - laboratory water quality
- ISO 385-1 - burette requirements
- ISO 6353-2 - reagent specifications
Keywords: ISO 2114, acid value, partial acid value, total acid value, polyester resins, paints and varnishes, titration, KOH, potentiometric titration, quality control.