Effect of fiber size on structural and tensile properties of electrospun polyvinylidene fluoride fibers

We use electrospinning to obtain polyvinylidene fluoride (PVDF) fibers and demonstrate simultaneous improvements in β-crystal microstructure and in tensile properties of fibers with reduction of their diameter. PVDF fibers with average diameters ranging from 70 to 400 nm are obtained by controlling the concentration of the polymer in the electrospinning solution. The amount of β-crystals present is found to be greater for finer diameter fibers, yielding a maximum β-phase fraction of 0.86 in the 70-nm fibers. Moreover, the deformation behavior of the fibers reveals that the tensile modulus and strength improve with reductions in fiber size. Sharp increases in tensile properties are demonstrated when the size of the fibers is reduced below 175 nm. We attribute the enhanced concentration of β-crystals and the tensile behavior of finer diameter fibers to the extensional forces experienced by the material during electrospinning.