ISO 9702 pdf download.Plastics – Amine epoxide hardeners – Determination of primary, secondary and tertiary amine group nitrogen content
1 Scope
This International Standard specifies a method for the determination of the primary, secondary and tertiary amine group nitrogen content of aliphatic or aromatic amine hardeners for epoxy resins.
2 Principle
2.1 Aliphatic amines 2.1 .I Determination of total amine group nitrogen content (XT) The total alkalinity is determined by potentiometric titration against hydrobromic or perchloric acid in glacial acetic acid, as described by the following reactions:The results are expressed as percentage nitrogen. NOTE 1 Perchloric acid is not suitable for use with amine hardeners such as Kaminoethylpiperazine. 2.1.2 Determination of tertiary amine group nitrogen content (X3) The primary and secondary amine groups are converted into amide groups with acetic anhydride, as described by the following reactions:The tertiary amine group alkalinity is determined by potentiometric titration against hydrobromic or per- chloric acid in glacial acetic acid/acetic anhydride, as described by the following reaction:The excess acetylacetone is determined by poten- tiometric titration against potassium hydroxide (the reaction products of acetylacetone and primary amine groups are neutral under these conditions). The results are expressed as percentage nitrogen.
NOTE 2 Weakly basic amines, such as 4,4’-diamino- diphenylsulfone, are titrated with hydrobromic or perchloric acid in glacial acetic acid. 2.2.4 Determination of primary amine group nitrogen content (XR~) The primary amine group nitrogen content is determined by calculating the difference between the total amine group nitrogen content and the sum of the secondary and tertiary amine group nitrogen contents. 2.2.5 Determination of secondary amine group nitrogen content (XR~) The secondary amine group nitrogen content is determined by calculating the difference between the sum of the secondary and tertiary amine group nitrogen contents and the tertiary amine group nitrogen content.
3 Reagents
During the analysis, use only reagents of recognized analytical grade and only distilled water or water of equivalent purity. 3.1 Acetic acid, glacial. 3.2 Acetic anhydride. 3.3 2,CPentanedione (acetylacetone). 3.4 /V,Ndiamethylformamide. 3.5 Acetylacetone, I,5 mol/l solution in N,Ndi- methylformamide. Dissolve 15 ml of acetylacetone (3.3) in 90 ml of N,N-dimethylformamide (3.4). 3.6 Salicylaldehyde. 3.7 Ethan-1,2-diol (ethylene glycol).3.8 Propan-2-01. 3.9 Ethylene glycol/propan-2-01 mixed solvent. Mix 500 ml of ethylene glycol (3.7) and 500 ml of propan-2-01 (3.8). 3.10 Potassium hydrogen phthalate. 3.11 Hydrobromic acid, 250 g/l solution in acetic acid. 3.12 Perchloric acid, 70 % or 60 % solution in water. 3.13 Potassium hydroxide. 3.14 Hydrochloric acid, concentrated. 3.15 Sodium carbonate. 3.16 Hydrobromic acid, 0,l mol/l standard volu- metric solution in glacial acetic acid. 3.16.1 Preparation Add 25 ml of hydrobromic acid (3.11 I slowly to 1 00 ml of glacial acetic acid (3.1) in a 1 000 ml brown-glass volumetric flask (4.9) and stir carefully. Dilute to the mark with glacial acetic acid. 3.16.2 Standardization Weigh out, to the nearest 0,l mg, 0,l g to 0,2 g of potassium hydrogen phthalate (3.10) and dissolve in 50 ml of glacial acetic acid (3.1). Titrate this solution potentiometrically against the solution of hydrobromic acid prepared in 3.16.1 Of,). Perform a blank test by titrating 50 ml of glacial acetic acid against the solution of hydrobromic acid prepared in 3.16.1 (Vz).3.17.1 Preparation Mix 8,5 ml of 70 % perchloric acid (or 9.9 ml of 60 % perchloric acid) (3.12) with 500 ml of glacial acetic acid (3.1) in a 1 000 ml brown-glass volumetric flask (4.9). Add 30 ml (or 35 ml if 60 % perchloric acid was used) of acetic anhydride (3.2) and mix well. Dilute to the mark with glacial acetic acid. 3.17.2 Standardization Use the same procedure as that in 3.16.2, calculating the concentration using the same equation. In this case, cl is the concentration of the perchloric acid solution prepared in 3.17.1. 3.18 Potassium hydroxide, 05 mol/l standard volu- metric solution in propan-Z-01. 3.18.1 Preparation Take 1 000 ml of propan-2-01 (3.8) in a round-bottomed flask and add 30 g of potassium hydroxide (3.13). Reflux for several hours to dissolve completely. Leave the solution in a carbon-dioxide-free atmosphere for a few days, then transfer the clear upper solution to a polyethylene bottle and keep it in the bottle equipped with a guard tube filled with soda lime. Take care that the solution does not touch a cork or rubber stopper or stopper grease, which may be saponified.