Quantitative Determination of PA6 and/or PA66 Content in Polyamide-Containing Wastes

Abstract

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.