Overview
ISO 9702:1996 specifies a laboratory method for determining the primary, secondary and tertiary amine group nitrogen content of aliphatic and aromatic amine hardeners for epoxy resins. The standard defines chemical conversions, titrations and calculation procedures to report each amine-type nitrogen content as mass percent nitrogen. It was prepared by ISO/TC 61 (Plastics), SC 12 (Thermosetting materials).
Key topics and technical requirements
- Scope: Quantitative determination of amine-group nitrogen in aliphatic or aromatic amine hardeners used with epoxy resins.
- Analytical principle:
- Potentiometric titration is the core measurement technique. Titrations use hydrobromic, hydrochloric or perchloric acid in glacial acetic acid or mixed solvent depending on amine type and basicity.
- Selective chemical conversions differentiate amine types:
- Primary amines → Schiff bases with salicylaldehyde or reacted with acetylacetone (to measure excess reagent).
- Primary and secondary amines → converted to amides with acetic anhydride (to leave tertiary amines measurable).
- Excess reagents are back-titrated (potassium hydroxide in propan-2-ol for acetylacetone excess).
- Reagents and apparatus: requires glacial acetic acid, acetic anhydride, acetylacetone, salicylaldehyde, dimethylformamide, standard acid/base solutions, a potentiometric titration setup with glass-calomel electrode, and controlled solvents (ethylene glycol/propan-2-ol mixed solvent).
- Sample sizing and blanks: Typical sample masses are chosen to contain ~0.001 mol amine groups; blank titrations are required for each step.
- Calculations and reporting: The standard provides formulae to convert titration volumes and concentrations into mass percent nitrogen for total, primary, secondary and tertiary amine groups. Results are reported to one decimal place.
- Special considerations: Perchloric acid is not suitable for certain amines (e.g., N‑aminoethylpiperazine); procedures differ for strongly vs weakly basic amines.
Applications
- Quality control and batch verification of amine hardeners used in epoxy resin formulation.
- Raw-material specification testing in adhesives, coatings, composites and electrical encapsulants manufacturing.
- R&D and formulation development where precise knowledge of amine-type distribution affects cure kinetics and performance.
- Regulatory or compliance testing where composition and traceability of curing agents must be documented.
Who should use this standard
- QC chemists and analytical laboratories in resin and hardener manufacturing.
- Materials scientists and formulation chemists working with thermosetting epoxy systems.
- Contract testing labs performing incoming inspection or supplier qualification.
- Standards committees and technical auditors assessing test method validity.
Related information
- Prepared by ISO/TC 61 (Plastics), Subcommittee SC 12 (Thermosetting materials). For practical implementation follow laboratory safety rules for strong acids (HBr, HCl, perchloric acid) and organic solvents.
Open preview (PDF)Plastics — Amine epoxide hardeners — Determination of primary, secondary and tertiary amine group nitrogen content
