EQUILIBRIUM THERMODYNAMICS OF THE TERNARY MEMBRANE-FORMING SYSTEM NYLON, FORMIC-ACID AND WATER

The binary Flory-Huggins interaction parameters for the ternary membra ne-forming system nylon, formic acid and water have been obtained from literature data, swelling values and melting point depression. Nylon 4,6 nylon 6 and a copolymer of nylon 4,6 and 6 were examined. The isot hermal crystallization boundaries were determined experimentally and t he binodal miscibility gap was calculated for these ternary systems. I t was found that the crystalline state is the thermodynamically favour able state for each system. Experimental data and calculated phase dia grams are discussed in relation to membrane formation. Although the th ermodynamic properties of the system dictate the phase separation that can take place, the kinetic parameters are of equal significance with respect to membrane formation. (C) 1996 Elsevier Science Ltd.