DEVELOPMENT OF NEW POLYETHYLENE HOLLOW FIBER MEMBRANE WITH ASYMMETRIC STRUCTURE USED FOR WATER RECYCLE SYSTEM

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1. Effect of extraction and drying on microporous polyethylene membrane structureTen different extractant and were used to remove mineral oil from polyethylene films and two different evaporation conditions were used to remove the extractant and produce microporous membranes. The dimension, microstructure and permeability of the membranes were used to measure the impact of extractant choice and drying conditions on the membrane morphology. The solubility parameters, boiling points and surface tensions of the extractants were related to the membrane morphology.2. Thermodynamic and kinetic studies on the poly (ethylene-co-vinyl alcohol) (EVOH) membrane formation by thermally induced phase separationThe liquid-liquid phase boundaries (binodal line) was shifted to higher temperature when ethylene content in EVOH increased. For EVOHs with ethylene content of 32-44 mol%, cellular pores were formed, while only polymer crystallization occurred for EVOH with 27 mol% ethylene content.3. preparation and Characteristics of polyethylene and EVOH hollow fiber membranes via thermally induced phase separationMicroporous PE and EVOH membranes were prepared by TIPS process. The effects of the experimental condition such as polymer molecular weight, air gap distance, cooling bath composition and ethylene content of EVOH on the membrane performance were investigated in detail.4. Simulation of asymmetric structure formation via thermally induced phase separationAsymmetric membranes having smaller pores at one side and larger pores at the other side were prepares by TIPS of polypropylene-diphenyl ether solution with polymer concentration gradient. The simulation of phase separation process by the spinodal decomposition was carried out based on Cahn-Hilliard model. The simulation results of pore size and the thickness of skin layer were approximately in agreement with the experimental results.