Overview
EN ISO 2114:2000 (ISO 2114:2000) specifies laboratory methods for determining the partial acid value and total acid value of polyester resins and binders for paints and varnishes. Intended for quality control, acceptance testing and R&D, the standard describes two titrimetric procedures (Method A and Method B) to quantify the milligrams of potassium hydroxide (KOH) required to neutralize 1 g of resin (reported as mg KOH/g). It is not applicable to phenolic resins. EN ISO 2114:2000 supersedes earlier editions (EN ISO 2114:1996 and EN ISO 3682:1998) and is endorsed by CEN.
Key Topics and Technical Requirements
- Definitions
- Acid value: mg KOH per g resin required for neutralization under test conditions.
- Partial acid value: neutralizes carboxyl-terminated groups, free acids plus half the free anhydrides.
- Total acid value: neutralizes carboxyl-terminated groups, free acids plus all free anhydrides.
- Principle
- Titration of free acids/anhydrides with standard KOH solution, potentiometrically or using an indicator.
- Methods
- Method A - solvent: toluene/ethanol mixture (2:1 by volume), potentiometric titration recommended; suitable for binders and unsaturated-polyester resins with low anhydride content.
- Method B - solvent: pyridine/methyl ethyl ketone/water; includes a 20-minute hydrolysis step to convert anhydrides before titration; suitable where free anhydrides are significant.
- Reagents & Titrant
- Standard KOH volumetric solution (commonly 0.10 mol/L in ethanol or methanol); concentration must be checked on day of use (Annex A).
- Solvent quality specified (anhydrous ethanol/methanol, low-water toluene, pyridine, MEK) and laboratory-grade water per ISO 3696.
- Apparatus
- Potentiometric titration setup (electrode + potentiometer), burette (25 ml), analytical balance (±1 mg), magnetic stirrer and standard glassware.
- Procedure highlights
- Select test portion mass based on expected acid value (table provided in standard); perform duplicate determinations and blank corrections; report results as mg KOH/g.
Applications and Users
- Quality control laboratories in paint, varnish and polyester resin manufacturing.
- R&D teams monitoring polycondensation reaction completion and polymer chemistry.
- Incoming material inspection for binders and coatings.
- Regulatory and standards compliance testing for product specifications.
Related Standards
- ISO 3251 - determination of non-volatile matter (paints/varnishes).
- ISO 3696 - water for analytical laboratory use.
- ISO 385-1 - burette requirements.
- Annex A of ISO 2114 provides the procedure to check KOH titrant concentration.
Keywords: EN ISO 2114:2000, ISO 2114:2000, acid value, partial acid value, total acid value, polyester resins, binders, paints and varnishes, potentiometric titration, quality control.