ABSTRACT
Melt-blown fibers (dav â¼1 µm) were produced from blends of poly(butylene terephthalate) (PBT) and a partially fluorinated random multiblock copolyester (PFCE) leading to enhanced hydrophobicity and even superhydrophobicity (static water contact angle = 157 ± 3°) of the associated fiber mats. XPS measurements demonstrated quantitatively that the surface fluorine content increased systematically with the bulk loading of PFCE, rising to nearly 20 atom %, which corresponds to 41 wt % PFCE at a bulk loading of 10 wt %. The PBT/PFCE fibers exhibit greater fluorine surface segregation than either melt-blown PBT/poly(ethylene-co-chlorotrifluoroethylene) (PBT/PECTFE) fibers or electrospun fibers obtained from blends of poly(styrene) and fluoroalkyl end-capped polystyrene (PS/PSCF). Dynamic contact angle measurements further demonstrated decreased surface adhesion energy of the melt-blown PBT/PFCE fiber mats due to the blooming of PFCE to the surface.
ABSTRACT
The wetting properties of poly(butylene terephthalate) (PBT) melt blown fibers were tuned by alkaline hydrolysis and subsequent fluorination. Fiber mats were exposed to a NaOH methanol solution for controlled periods of time at several temperatures, resulting in surface hydrolysis (h-PBT). Subsequent simple solution chemistry was applied to the h-PBT fibers, leading to fluorination of the surface (f-PBT) and the transformation of the wetting properties of the material. Electron microscopy revealed that hydrolysis leads to a textured surface that is retained in the fluorinated product. Sessile drop wetting measurements demonstrated superhydrophilicity for the h-PBT fiber mats and sticky superhydrophobicity with the f-PBT fiber mat.
ABSTRACT
Nanofibers were generated by melt blowing three sets of polymer blends, each comprised of pairs of immiscible components. Blends containing minority phases (25% by volume) of poly(ethylene-co-chlorotrifluoroethylene) (PECTFE) in poly(butylene terephthalate) (PBT), PECTFE in poly(styrene) (PS), and PBT in PS were dispersed as droplets in a continuous majority phase and melt blown into long (>100 µm) fibers with average diameters of several micrometers. Electron microscopy experiments revealed that melt blowing transformed the initial spherical dispersions into a nanofiber-in-fiber morphology. Macroscopic mats of nonwoven PBT and PECTFE nanofibers, with average diameters as small as 70 nm, were isolated by selectively removing the majority phase with a solvent. This method provides a potentially inexpensive, high throughput, one-step route to scalable quantities of polymeric nanofibers.
