Dissolution and gasification behavior of thermosetting resin in molten alkali hydroxide

Dissolution and gasification behavior of thermosetting resin in molten alkali hydroxide was examined to design a gasification recycle system. Effective recycling methods have not yet been established for thermosetting resins, which are predominantly incinerated, landfilled, or exported overseas. The dissolution behavior of thermosetting resins, phenolic, polyurethane and epoxy resins, in molten alkali hydroxide was examined by dissolving them as organic carbon in molten alkali hydroxide to reduce the volume and convert them into fuel gases, such as hydrogen and methane. Sodium hydroxide (NaOH) and potassium hydroxide (KOH) were mixed in weight ratios of 1 : 0, 3 : 1, 1 : 1, 1 : 3, and 0 : 1 to prepare alkali hydroxide with various Na and K ratios, and then the sample (0.22 g) was added into a cylindrical reactor together with each alkali hydroxide, heated at 150-350 °C for approximately 10 min and maintained at the target temperature for 60 min (total heating time: 70 min). The residual percentage of resin and dissolved contents of organic and inorganic carbon in molten alkali hydroxide were examined. For all mixing ratios of alkali hydroxides, polyurethane and epoxy resins were almost completely decomposed at higher than 300 °C. Polyurethane decomposed at a lower temperature than epoxy resin, and phenolic resin was hardly decomposed. The highest amounts of organic carbon dissolved from polyurethane and epoxy resin were 508 mg g^-1 at 250 °C and 427 mg g^-1 at 300 °C, respectively. Epoxy resin was heated at 500 °C to promote gasification of hydrogen and methane.