THE MORPHOLOGY CHARACTERIZATION AND PERFORMANCE OF DENSE PPO MEMBRANES FOR GAS SEPARATION

Dense membranes were prepared from poly(2,6-dimethyl-1,4-phenylene oxi de) (PPO) using different solvents, that is, carbon disulphide, benzen e, 1,1,2-trichloroethylene (TCE), toluene, chlorobenzene and bromobenz ene. The membranes were characterised by atomic force microscope (AFM) , electron spin resonance (ESR) and Raman scattering. The permeation d ata for N-2, O-2, CO2 and CH4 was taken by using a constant volume sys tem. It was observed that the PPO membrane prepared by using carbon di sulphide as a solvent (PPO-CS2) had a entirely different surface morph ology when compared with the surface of the membranes prepared by usin g other solvents. The PPO-CS2 membrane's surface layer contained super nodular aggregates of size 1.199 mu m in diameter. These super nodula r aggregates consisted of nodules of size about 43.0 nm. In contrast n o super nodular aggregates were observed in the other membranes. Inter estingly, both selectivity and permeability of the PPO-CS2 membrane we re far superior to the other membranes. The physical properties, boili ng point (BP), surface tension and viscosity of solvents used for the preparation, were correlated to the data from membrane characterisatio n as well as permeation experiments. Permeability increased and the se lectivity (O-2/N-2 and CO2/CH4) decreased with an increase in the BP. A similar trend was observed for other properties. Regarding the rough ness parameter of the membranes, it depended also on the physical prop erties of the solvents used. Generally, it increased with an increase in the BP of the solvents used. A similar trend was observed for other physical properties. The number of spins/g was less in the PPO-CS2 an d PPO-TCE membranes compared with benzene or its derivatives. It was o bserved that in the presence of CH4 and N-2 the number of spins/g was always higher than CO2 and O-2 respectively.