Deformation modeling of polyvinylidenedifluoride (PVDF) symmetrical microfiltration hollow-fiber (HF) membrane

The tensile deformation behavior of polyvinylidenedifluoride (PVDF) symmetrical microfiltration hollow-fiber (HF) membranes was studied. The membranes had submicron pores with a three-dimensional open-cell structure. The surface and cross section of the porous membranes were observed by FESEM (field emission scanning electron microscope) to investigate the microstructure of the cell, namely, its size and ligament geometry. During uniaxial tensile tests, the membranes underwent elastic deformation and plastic deformation. Large deformation induced pore growth along the tensile direction, resulting in an increase in water permeability. In order to establish a mechanical model for tensile deformation, the finite element method (FEM) was employed. In this model, the Kelvin polyhedron (truncated octahedron structure) was used to mimic a three-dimensional open-cell structure. A one-unit cell based on this structure was created, and a periodical boundary condition was employed for the FEM computation. The FEM model could reproduce the overall elastoplastic deformation behavior of the porous membrane and provide useful insight into the fabrication of porous membranes and reliable operation of water purification.