Foreword I
1 Scope 1
2 Terms and definitions 1
3 Principle 1
4 Reagents 1
5 Apparatus 3
6 Procedure 3
7 Expression of results 4
8 Precision 5
9 Test report 5
Annex A (Normative) Modification applicable to epoxyamines 6
Annex NA (Informative) Precision 8
Plastics—Epoxy compounds—Determination of epoxy equivalent
1 Scope
This standard specifies a method for the determination of epoxy equivalent and is applicable to all epoxy compounds. In the case of epoxyamines, it is necessary to apply the modification specified in Annex A.
2 Terms and definitions
For the purpose of this standard, the following terms and definitions apply.
2.1 epoxy equivalent
EE
the mass of resin, in grams, which contains one mole of epoxy groups
2.2 epoxy index
EI
the number of moles of epoxy groups contained in 1 kg of resin
3 Principle
The epoxy groups in a test portion are reacted with nascent hydrogen bromide produced by the action of 0.1 mol/L standard volumetric perchloric acid solution on tetraethylammonium bromide. The end-point is determined either using crystal violet as indicator or by a potentiometric method.
4 Reagents
During the analysis, use only reagents of recognized analytical grade.
4.1 Glacial acetic acid.
4.2 Acetic anhydride, purity>96%.
4.3 Chloroform.
4.4 Potassium hydrogen phthalate.
4.5 Crystal violet, indicator solution.
Dissolve 100 mg of crystal violet in 100 mL glacial acetic acid (4.1).
4.6 Perchloric acid, 0.1 mol/L standard volumetric solution.
