An approach to chemical recycling of epoxy resin cured with amine using nitric acid

An approach to chemical recycling of epoxy resin was pursued. Bisphenol F type epoxy resin cured with 1,8-p-menthanediamine could be completely decomposed in nitric acid solution resulting from low corrosion resistance to nitric acid. Organic decomposed products of the resin with the highest yield were extracted from neutralized solution. The extract was repolymerized to prepare recycled resin, mixed with bisphenol F type epoxy resin and curing agent of phthalic anhydride. The mechanical properties of virgin resin and recycled resins were compared. It was surprising that the recycled resins were far superior to the virgin resin in strength. The results obtained from differential scanning calorimeter (DSC) showed that the glass transition temperature (Tg) of recycled resins was higher than that of virgin resin. The reason that they formed the better network structure was discussed.