Nylon 11 and Nylon 12 are commercially important polymers due to their unique combination of mechanical strength, chemical resistance, and processability. Products have been prepared from these polymers via thermally induced phase separation (TIPS) for many years. Nevertheless, known diluents for Nylon 11 and 12 pose specific processing problems, and it would be desirable to find a diluent that allows low processing temperatures, has a high flash point, is inexpensive, and exhibits low toxicity. This work investigated a variety of alternative diluents not previously documented in the literature. A fundamental study was also performed to determine which factors are important in selecting a diluent for preparing Nylon liquid–liquid TIPS membranes. The information gathered in this study, including phase diagrams for all feasible systems investigated, will be important in shaping future formulation work for Nylon use in microporous membranes. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43237.

Nylon 11 and Nylon 12 have been studied for many years for the purpose of fabricating microporous films. Unfortunately, these polymers have somewhat unique properties that prevent the films from exhibiting porous surfaces when their solutions undergo thermally induced phase separation by quenching in water. Without surface pores, these films have limited utility as water purification membranes. In this work, application of high temperature diluent coatings to the surface prior to quenching is shown to enable the formation of surface porosity in Nylon 11 and Nylon 12 films. Furthermore, the pore sizes achieved are suitable for ultrafiltration applications. Following successful lab-scale coating experiments, the effects of coating thickness, temperature, and solvent type on surface morphology are demonstrated over five film extrusion trials.