Studies on the oxidative degradation of nylons by nitrogen dioxide in supercritical carbon dioxide

Abstract Oxidative degradation of nylons was carried out using nitrogen dioxide (NO 2 ) as the oxidizing agent and supercritical carbon dioxide (scCO 2 ) as the reaction medium. Seven typical nylons were studied: three ring opening polymerization type nylons (nylon-6, -11 and -12) and four condensation co-polymerization type nylons (nylon-4/6; -6/6; -6/9 and -6/12). All the nylons decomposed in the NO 2 /scCO 2 system under relatively mild conditions (140 °C, 1 h, and 10 MPa) and provided aliphatic α, ω-diacids such as succinic, glutaric and adipic acids in good yields. The product distribution of these α, ω-diacids strongly depended on the reaction conditions such as temperature, time and amount of NO 2 , but not on the total pressure. Furthermore, the proportions of the products were affected by the type of nylon. A mechanism is proposed and a detailed discussion regarding the degradation of nylon in the NO 2 /scCO 2 system is provided.