Preparation of Hydrophilic Polypropylene/Polyvinyl Butyral Hollow Fiber Membranes by Melt-spinning-stretching

Polyvinyl butyral (PVB) as hydrophilic modification agent and polypropylene-g-maleic anhydride (PP-g-MAH) as a compatibilizer were blended with polypropylene (PP) in order to prepare hydrophilic PP/PVB hollow fiber membranes by melt-spinning and stretching(MS-S). The effect of PVB at different mass ratios on crystallization behavior and hydrophilicity of PP/PVB blends was investigated by differential scanning calorimeter(DSC) and water contact angle (WCA). The wide angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS) were used to analyze the effect of PVB at different mass ratios on the crystalline lamellar structure of PP/PVB hollow fiber after annealed. The pore dimensions and distribution of inner surface of PP/PVB hollow fiber membranes were measured using field emission scanning electron microscope (FESEM). In addition, the porosity and pure water flux of PP/PVB hollow fiber membranes were tested. The results showed that the hydrophilicity of PP/PVB blends was improved obviously because of WCA of PP/PVB blends reduced from 103 degrees to 76 degrees with the increase of PVB. At the same time, PVB accelerated the nucleation rate of PP because of PVB acted as heterogeneous nucleation effective. However, the maleic anhydride of PP-g-MAH was chemically bound to hydroxy of PVB, which also delayed the motion of molecular chain and leaded to imperfect crystal structure, especially excessive addition of PVB. The results confirmed WAXD and SAXS analysis. The crystallinity of PP/PVB2. 5 (2. 5% PVB) hollow fiber was better than that of pure PP hollow fiber after annealed. The lamellar orientation, lamellar thickness, and structure of Shish-Kebab of PP/PVB2. 5 hollow fiber were better than that of pure PP hollow fiber after annealed. The porosity of corresponding hollow fiber membrane was 66% and pure water flux was 320 L/(m(2) . h) , which increased by 76. 8% compared with that of the pure PP hollow fiber membrane.