PREPARATION AND ANALYSIS OF THIN POLYSULFONE FILMS UNDER HIGH AND LOWGRAVITATIONAL-FIELD ENVIRONMENTS

The formation of a polymer membrane structure via a solvent casting pr ocess is strongly influenced by the rate of solvent removal from the c asting solution, the time required to form a thin polymeric layer or s kin on the casting solution surface and quenching or exposure of the c asting solution to a nonsolvent media. The physical-chemical processes associated with the formation of the membrane are diffusion, mass tra nsfer, convection and precipitation. This study is concerned with a so lvent evaporation process that creates thin polysulfone polymer membra ne structures that have pore sizes around 1800 Angstrom. The solvent e vaporation and the polymer/solvent concentration variables were held c onstant and the only major variable was the gravitational environment which was varied between 2 and 10(-5) a. A theoretical model was ident ified which correlated the mass transfer coefficient (k(c)) of the sol vent removal process with the gravitational environment. Low gravitati onal fields were observed to reduce the ability of the solvent to be r emoved from the polymer coating solution which strongly influenced the final morphology of the resulting polysulfone membrane film. The inte nt of this research program was to better understand the influence of a gravitational field on certain parameters important to the commercia l preparation of membrane structures in a ground base environment.