Modified poly(vinylidene fluoride) hollow fiber composite membranes reinforced by hydroxyapatite nanocrystal whiskers

The modified poly(vinylidene fluoride) (PVDF) hollow fiber composite membranes reinforced by hydroxyapatite (HAP) nanocrystal whiskers were fabricated with wet-spinning method. The PVDF/HAP/N-methyl-2-pyrrolidone dope solutions experienced delayed demixing mechanism, and the precipitation rate slightly increased as the HAP whisker content increased. The cross sections of PVDF-HAP and neat PVDF hollow fiber composite membranes were composed of five distinct layers: two skin layers, two finger-like sublayers, and a sponge-like layer. The Young's modulus of and tensile strength of the PVDF-HAP hollow fiber membranes gradually increased with the addition of nano-HAP whiskers. The elongation ratio was also improved, which was different from the polymeric membranes modified by other inorganic nanofillers. The permeation flux of the PVDF-HAP hollow fiber membranes slightly increased with the increase of HAP content in the composite membranes as its hydrophilicity was improved. The crystallization behaviors of PVDF in the composite membranes were also investigated. (c) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013