Pure component recovery from polyamide 6/6 6 mixtures by selective dissolution and reprecipitation

A selective dissolution/reprecipitation technique was applied for the effective recovery of Polyamide 6 (PA 6) and Polyamide 6 6 (PA 6 6) from their mixtures. The proposed process comprises mainly selective polyamide dissolution in an appropriate solvent at a specific temperature, reprecipitation of the polymer from the solution by addition of a nonsolvent, washing, and drying. A model mixture of virgin PA 6 and PA 6 6 pellets was initially tried, whereas in a following stage the selective dissolution technique was applied for the recovery of a PA‐copolymer layer from a three‐layered bottle end product also containing HDPE and EVA. End‐group analysis, dilute solution viscometry, and differential scanning calorimetry were used to assess the molecular weight preservation and crystallizability of the recycled polyamides. The recycled materials demonstrated excellent retention of the properties studied, although in the copolymer case, due to hydrolysis, a molecular weight decrease was detected, accompanied with a slight compositional shift, favoring the PA6 6 presence in the final product. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1924–1930, 2002