Structural properties and superhydrophobicity of electrospun polypropylene fibers from solution and melt

Isotactic polypropylene (iPP) has successfully been electrospun from both solution and melt using an elevated temperature setup. First, PP nanofibers with two different average diameters (0.8 μm and 9.6 μm) were obtained via electrospinning of iPP in decalin, and the effect of deformation and solidification on the morphological and structural features of the resulting fibers was studied. Secondly, melt electrospun PP fibers with two different average diameters were also fabricated to compare the structures with those of solution electrospun PP fibers. DSC and XRD results show that β form crystals which can increase the impact strength and toughness of electrospun fibers are present in sub-micron scale PP fibers from solution, while fibers from melt mostly show α form crystals. The annealed fibers have changed their morphological forms into α and γ crystal forms. Finally, it is observed that electrospun PP fiber webs both from solution and melt exhibit superhydrophobicity with a water contact angle about 151° which is substantially higher than those of a commercial PP non-woven web and a compression molded PP film, 104° and 112°, respectively. Such superior hydrophobicity was observed for all PP electrospun fibers and it was not altered by the processing scheme (solution or melt) or fiber diameter (sub-micron or micron). Enhanced hydrophobicity of electrospun PP fiber webs contribute to excellent barrier performance without losing permeability when they are applied to protective clothing.