Polarization treatments of electrospun PVDF fiber mats

Abstract

Nanostructured materials such as electrospun fibers are used as filters in many applications. Functionalization techniques can affect the filter performance characteristics such as fiber diameter, pore size, thickness and surface charge. Polyvinylidene fluoride (PVDF) is well known for its piezoelectric properties and its α, β, γ, δ, and ε crystalline phases. The β crystalline phase exhibits the most polar phase and has higher dipole moment upon mechanically stretching of the polymer. This paper uses a custom-made heat-stretch-poling method to polarize electrospun PVDF fibers. Effects of various polarization -treatments such as stretching, heating and electrical poling on filter characteristics as well as on β-phase were studied individually and as a combination of treatments. As-spun and polarized samples were characterized for pore size distribution, charge, and mat thickness respectively. It was observed that most of the treatments had a significant impact on filter performance but little to no impact on β-phase content as electro-spinning alone resulted in relatively high 83% β-phase content.