We report on a simple and efficient chemical recycling process for aliphatic polyamides (PA 66, PA 1010, PA 11, and PA 12), whereby PAs are converted exclusively into their constituent monomers even in the presence of reinforcement additives, such as carbon- and glass-fibers. In this process, the rate of PA hydrolysis reaction, performed under microwave irradiation in the presence of HCl as an acid catalyst, depends on the PA type, the HCl/amide mole ratio, and the type and amount of reinforcement additives. PA 66 is completely converted into the constituent monomers at 200 °C and a 1.25 HCl/amide mole ratio in 10 min. Long-chain PAs (PA 11, PA 12, and PA 1010) and PAs containing glass- or carbon-fiber reinforcement additives need at the same experimental conditions longer reaction times. Alternatively, they can be completely hydrolyzed at 200 °C within a comparable reaction time at a higher HCl/amide mole ratio of 2.5. Complete and straightforward conversion of PAs into the constituent monomers in the absence of side reactions simplifies the isolation and purification of monomers and reinforcement additives, which have been recovered in high yields and quality comparable to those of commercially available chemicals.

A fast, robust, and convenient method for quantitative determination of polyamide-6 (PA6) and polyamide-66 (PA66) in plastic wastes is presented. The method includes a straightforward procedure for complete hydrolysis of polyamides (PAs) into the constituent monomers and their quantitative determination in hydrolyzates by high-performance liquid chromatography on a mixed-mode column, from which the contents of a particular PA are determined. The method was developed on neat PA6 and PA66 as well as their mixture and was further utilized on PA-based composites and postconsumer wastes (carpet and fishing net wastes) containing PA in different amounts. The information on the content of a particular PA type in plastic wastes is important because it determines the maximum recovery of PA constituent monomer(s) by chemical recycling and consequently suitability of waste as a feedstock. Moreover, the proposed method allows for convenient differentiation between PA6 and PA66 in their mixtures, which is difficult to assess with precision by conventional characterization techniques.