| Microporous polymeric membranes of improved thermal stability and chemical resistance were formed via Thermally Induced Phase Separation (TIPS) process. Specifically, poly(phenylene sulfide) (PPS) membranes were formed using 4-benzoylbiphenyl (BBP) as the diluent. The overall objective of the proposed research was to produce porous PPS membranes by the solid-liquid TIPS process. Specifically, the objective was to investigate the feasibility of controlling membrane structure by controlling the nucleation density ({dollar}eta{dollar}). Control over {dollar}eta{dollar} (hence the morphology) was achieved by choosing proper combinations of process parameters, such as polymer concentration, dissolution temperature, crystallization temperature, dissolution time, and crystallization time. Differential Scanning Calorimetry (DSC), Scanning Electron Microscopy (SEM) and optical microscopy (OM) were used to obtain the required data. A new mathematical model was developed to predict the {dollar}eta{dollar} for a polymer-diluent system. The new model overcomes the limitations imposed by the simplified Avrami equation. The new model differs from the classical Avrami theory in its treatment of the dependence of growth probabilities on the change in polymer concentration as crystallization develops. The theory includes treatment of both homogeneous and heterogeneous nucleation, arbitrary growth shapes (e.g., axialites), and secondary crystallization. With the developments presented in this dissertation, process engineers can easily select the correct process parameters to fulfill the specifications of microporous membranes for specific applications. |
