Hycat AO-4 (or equivalent) is a clear and colorless product used to promote the reaction of epoxy/anhydride formulations that require exceptional clarity and light transmission characteristics in the final cure. Hycat AO-4 (or equivalent) provides very long epoxy pot life and produces moderate to high glass transition temperatures. Composition: Epoxy resin EPIKOTE 828 with hardener Methylhexahydrophthalic Anhydride (MHHPA) and catalyst Hycat AO-4 (or equivalent) should not turn yellow at curing temperature T = 140 C