Rapid microwave induced depolymerization of polyamide-6

Polyamide-6 (PA-6) depolymerization was performed using microwaves as the energy source for the acid catalysed hydrolysis, with phosphoric acid as the catalyst. Microwave irradiation of 200 W was applied for 12–23 min to a reaction mixture in a sealed reaction vessel. After 15 min of irradiation PA-6 was completely solubilized. The product mixture consisted of more than 90% ϵ-aminocaproic acid (ACA) and its linear oligomers, with a minor part consisting of cyclic products. The product mixture was analysed by chromatographic and spectroscopic methods. With longer irradiation time or more acid, there was a shift toward higher concentrations of ACA and its dimer, as well as a decrease in the concentrations of higher oligomers.