Crystallization and dissolution behaviour of polyamide 6-water systems under pressure

The solubility of polyamide 6 (PA6) in water under pressure has been reported recently and is explored further here using a pressurized differential scanning calorimeter equipped with a pressure regulator, enabling operation at constant pressure. The optimum parameters for solubility (temperature, pressure, concentration) were determined. Crystallization and melting temperature depressions of a maximum of 60 degrees C were found. The minimum water concentration needed to reach the maximum temperature depression was found to be approximately 30 mass%. Because in such a case the end melting/dissolution temperature for PA6 in water is approximately 165 degrees C, the pressure level has to be high enough to prevent water from evaporating, i.e. above 8 bar (0.8 MPa). The expected industrial uses of the water solubility of polyamides under pressure are to ease the processing of polyamides by extrusion; to make polyamide composites; to disperse temperature-sensitive fillers in polyamides; and, in general, to realize 'green' routes for the formation of polyamides. (C) 2010 Society of Chemical Industry