Thermodynamic Modeling of PES/CA Blend Membrane Preparation

Thermodynamic behavior of quaternary system with one low molecular weight component; N –Methylpyrrolidone (NMP) as a solvent, non-solvent; polyethylene glycol (PEG 400) and two high molecular weight polymers; polyethersulfone (PES) and cellulose acetate (CA) was investigated. An extended modified Flory-Huggins model was used. The predicted results from model of critical temperature for superiority properties of polymer blend solution were in range between UCST 323 K and LCST 350 K. However, the increasing the vaporization time of PES/CA blend membrane to 30 min has increased the heat of vaporization to 133659.6 J/mole which led to increase in cohesive energy density to 1311.82 J/cm3 and gained more solvent evaporation. The diffusion model was studied on the immersion precipitation process which was indicated that solvent and non-solvent volume fractions increased with time in the coagulation bath , while the polymer solution volume fraction decreased due to solvent and non-solvent removal from polymer solution and blend membrane formation. The predicted results from model of heat treatment process on blend membrane were indicated that increasing in membrane thickness and formation of dense layer in blend membrane