Chemical recycling bisphenol A type epoxy resin based on degradation in nitric acid

The method for recycling of bisphenol A type epoxy resin based on degradation in nitric acid was investigated. It examined chemical recycling of bisphenol A type epoxy resin cured with 1,8-menthandiamine. The immersion temperature was controlled at 80 degrees C in 4M and 6M nitric acid and three kinds of products were recovered. Size exclusion chromatography and FT-IR analysis were conducted to investigate the molecular weight distributions and chemical structures of the recovered products. The results of these analyses showed that the extract possessed high yield and was employed for repolymerizing process. To prepare recycled resin the same bisphenol A type epoxy resin and the curing agent phthalic anhydride were chosen. Neutralized extract was added to this epoxy system, then the mechanical properties and thermal properties were evaluated and compared with virgin resin. The results obtained from the differential scanning colorimeter (DSC) and three-point bending test showed that the recycled resin has much higher glass transition temperature (Tg) and mechanical strength. It was concluded that recycled resin formed a better network structure and mechanical strength than virgin resin.