EN ISO 7327:1997

Plastics - Hardeners and accelerators for epoxide resins - Determination of free acid in acid anhydride (ISO 7327:1994)

Publication date:   Jun 30, 2004

Scope

The principle of the method specified is reacting a small amount of free acid present in a test portion of acid anhydride hardener or accelerator with rhodamine 6G to colour the test solution pink, measuring the absorbance of the coloured solution at a wavelength of about 510 nm using a spectrometer, determining the free-acid content from a calibration curve. The method is suitable for most anhydrides except for polyester and oligomeric anhydrides which may give too wide a scatter of results.