Preparation And Properties Of PMP Hollow Fiber Membranes

Poly(4-methyl-l-pentene) (PMP) is a kind of polyolefin with excellent performance. It is often used in membrane oxygen enrichment due to its eximious gas permeability and perm-selectivity of oxygen and nitrogen. Commercial PMP hollow fiber membrane is normally prepared by immersion precipitation phase inversion process. Due to the following advantages of the melt-stretching (MS) method: solvent-free, non-pollution, and excellent mechanical strength of the prepared membrane etc., we hope to prepare PMP hollow fiber membrane with good performance by MS method after optimizing the fabrication processing.This thesis focuses on the fabrication processing of PMP hollow fiber membrane. Various influencing factors are investigated, including melting temperature, discharging speed, take-up speed, temperature at the 0-0.5 m region under the nozzle, annealing temperature, annealing time, draw ratio, and so on. The structure of PMP membrane is characterized by differential scanning calorimetry (DSC) and scanning electron microscope (SEM). Through testing the crystallinity, mechanical performance, surface morphology, gas permeability and selectivity of oxygen and nitrogen, the relationship between property and structure of PMP hollow fiber membrane is studied.Polypropylene (PP) hollow fiber membrane is widely used in water treatment industry. It is found that the aging rate of PP membrane is accelerated when PP membrane is applied in seawater desalination pretreatment, resulting in shorter service lifetime. The structure evolution of PP membrane before and after the seawater desalination is characterized by Fourier infrared spectrum, thermo-analysis, and scanning electron microscope. The reason leading to the decreased strength of the PP membrane after the application in seawater desalination is investigated by control experiments. The results indicate that it is the oxidation of hypochlorite in seawater that causes the decreased strength of PP membrane. To avoid the accelerated aging of the PP membrane used in seawater desalination, some measures were put forward based on the discussion in this article.