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A simple and effective method for the fabrication of porous nanofibers based on the solvent evaporation methods in one-step electrospinning process from the commercial polyvinyl butyral (PVB) is presented. The obtained nanofibers are prevalently amorphous with diameters ranging from 150 to 4350 nm and specific surface area of approximately 2–20 m2/g. Pore size with irregular shape of the porous PVB fibers ranged approximately from 50 to 200 nm. The effects of polymer solution concentration, composition of the solvents mixture, and applied voltage on fiber diameter and morphology were investigated. The theoretical approach for the choice of poor and good solvents for PVB was explained by the application Hansen solubility parameter (HSP) and two-dimensional graph. Three basic conditions for the production of porous PVB nanofibers were defined: (i) application of good/poor solvent mixture for spinning solution, (ii) differences of the evaporation rate between good/poor solvent, and (iii) correct ratios of good/poor solvent (v/v). The diameter of prepared porous PVB fibers decreased as the polymer concentration was lowered and with higher applied voltage. These nanofiber sheets with porous PVB fibers could be a good candidate for high-efficiency filter materials in comparison to smooth fibers without pores.

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The new electrospinning technology Nanospider TM , offering a real potential for industrial production of nanofibers, is used for the preparation of nanofiber sheets from aqueous solutions of polymer blends. The nanofiber sheets are prepared from a mixture of chitosan and polyethylenoxide (PEO) and using the novel continual electrospinning process (Jirsak et al., 2005, www.nanospider.cz) affords a network with typical fiber diameters that are less than 500 nm. Effects of solvents, molecular weight of both polymers, monovalent salt, surfactant and composition of chitosan blend on electrospinning are also studied.The optimal conditions for electrospinning by the Nanospider TM technology, including applied high voltage, distance between both electrodes, air temperature and air humidity, are also found. The crosslinking of the nanofiber sheet is achieved by heat treatment. The morphology of electrospun fibers is observed by using a scanning electron microscope (SEM). Chitosan in the nanofiber sheets format has a great potential to be widely used in various applications derived from its biocompatibility and biodegradability.