Industry News: Usually we do not have a simple specific test method for the cross-linked units in the converted epoxy groups or cured epoxy resins. The Gibbs indophenol test of epoxy resin to phenol is a positive reaction (due to the presence of bisphenol A). Contrary to phenol resin, the chromic acid test for formaldehyde is a negative reaction. The following are two methods for identifying high-quality epoxy resins.
1. When thermal cracking is performed below 260°C, all epoxy resins will produce acetaldehyde. The steps are as follows: put the test in a pyrolysis tube, cover the mouth with a newly prepared 5% sodium nitrocyanide and morpholine aqueous solution filter paper, and heat to 240°C in an oil bath. When the gas released by thermal cracking passes through the filter paper. The filter paper turns blue to indicate epoxy resin.
2. The epoxy method can also be used to identify the epoxy resin: at room temperature, take about 100 mg of resin in about 10 ml of concentrated sulfuric acid, and then add about 1 ml of concentrated nitric acid. Five minutes later, carefully add 5% aqueous sodium hydroxide to the top of the solution. If bisphenol A epoxy resin grease is present, the interface of the two layers of solution will appear cherry red.