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.
Status: PublishedPublication date: 1994-07
Edition: 1Number of pages: 3
Technical Committee: ISO/TC 61/SC 12 Thermosetting materials
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