Effects of electrospinning parameters on polyacrylonitrile nanofiber diameter: an investigation by response surface methodology

Effects of material and process parameters on the diameter of electrospun polyacrylonitrile fibers were experimentally investigated. Response surface methodology (RSM) was utilized to design the experiments at the settings of solution concentration, voltage and the collector distance. It also imparted the evaluation of the significance of each parameter on the resultant fiber diameter. The investigations were carried out in the two-variable process domains of several collector distances as applied voltage and the solution concentration were varied at a fixed polymer molecular weight. The mean diameter and coefficient of variation were modeled by polynomial response surfaces as functions of solution concentration and voltage at each collector distance. Effect of applied voltage in micron-scale fiber diameter was observed to be almost negligible when solution concentration and collector distance were high. However, all three factors were found statistically significant in the production of nano-scale fibers. The response surface predictions revealed the parameter interactions for the resultant fiber diameter, and showed that there is a negative correlation between the mean diameter and coefficient of variation for the fiber diameter. A sub-domain of the parameter space consisting of the solution concentration, applied voltage and collector distance, was suggested for the potential nano-scale fiber production

Piezoelectric ultrafine polymer and ceramic fibers by electrospinning: process development and characterization

Piezoelectric polymer and ceramic films and fiber mats that may be considered for actuator and sensor needs were fabricated. Solution casting and electrospinning were utilized for Poly(vinyldene fluoride) (PVDF) films and fiber mats, respectively, while zinc oxide (ZnO) fiber mats were fabricated by electrospinning process followed by calcination. Morphology, crystalline structure and mechanical properties of the piezoelectric films and fiber mats were examined and characterized for experimentbased process optimization. Traditional solution casting process produces uniform PVDF films yet with nonpolar crystallinity. Stretching of the solution cast films were carried out to increase the polar crystal phase of PVDF. Stretched and un-stretched PVDF films were characterized according to their polar crystallite contents, and stretching was shown to be vital for β-phase formation in favor of piezoelectricity. Electrospinning process produces mats of ultrafine fibers with diameter ranging from a hundred nanometers to a couple of micrometers, by applying an electrical force to polymer solution. The effects of solvent type, solvent mixture together with applied voltage and collector distance were investigated leading to process parameter ranges to produce planar mats composed of uniform fibers only. All of the parameters were found to have vital roles in the fabrication of fiber mats regarding their morphology and applicability without self-folding and fiber uniformity. In addition, crystallinity, morphology, mechanical property and potential piezoelectric effect of solution cast and electrospun films were analyzed and compared. Electrospun fiber mats were found to be advantageous as in-situ β-phase formation was observed. Nano-scale zinc oxide fibers were also produced by electrospinning, but followed by calcination. Processing conditions such as solution content and heat treatment schemes were optimized in order to obtain uniform ZnO nanofibers. Zinc concentration and the substrate that the sample is placed on were found to be significant towards the uniformity and continuity of the ceramic fibers. Heating rate during calcination was also shown to be effective in fiber morphology and geometry. Fibers of ZnO with ~140nm diameter were produced. In addition, micron-scale ZnO whiskers and rods were also formed during the calcination process

Poly(vinylidene fluoride)/zinc oxide smart composite material

This work aimed at fabrication and electromechanical characterization of a smart material system composed of electroactive polymer and ceramic materials. The idea of composite material system is on account of complementary characteristics of the polymer and ceramic for flexibility and piezoelectric activity. Our preliminary work included Polyvinylidene Fluoride (PVDF) as the flexible piezoelectric polymer, and Zinc Oxide (ZnO) as the piezoelectric ceramic brittle, but capable to respond strains without poling. Two alternative processes were investigated. The first process makes use of ZnO fibrous formation achieved by sintering PVA/zinc acetate precursor fibers via electrospinning. Highly brittle fibrous ZnO mat was dipped into a PVDF polymer solution and then pressed to form pellets. The second process employed commercial ZnO nanopowder material. The powder was mixed into a PVDF/acetone polymer solution, and the resultant paste was pressed to form pellets. The free standing composite pellets with electrodes on the top and bottom surfaces were then subjected to sinusoidal electric excitation and response was recorded using a fotonic sensor. An earlier work on electrospun PVDF fiber mats was also summarized here and the electromechanical characterization is reported

Effects of electrospinning parameters on polyacrylonitrile nanofiber diameter: an investigation by response surface methodology

Effects of material and process parameters on the diameter of electrospun Polyacrylonitrile fibers were experimentally investigated. Response surface methodology (RSM) was utilized to design the experiments at the settings of solution concentration, voltage and the collector distance. It also imparted the evaluation of the significance of each parameter on the resultant fiber diameter. The investigations were carried out in the two-variable process domains of several collector distances as applied voltage and the solution concentration were varied at a fixed polymer molecular weight. The mean diameter and coefficient of variation were modeled by polynomial response surfaces as functions of solution concentration and voltage at each collector distance. Effect of applied voltage in micron-scale fiber diameter was observed to be almost negligible when solution concentration and collector distance were high. However, all three factors were found statistically significant in the production of nano-scale fibers. The response surface predictions revealed the parameter interactions for the resultant fiber diameter, and showed that there is a negative correlation between the mean diameter and coefficient of variation for the fiber diameter. A sub-domain of the parameter space consisting of the solution concentration, applied voltage and collector distance, was suggested for the potential nano-scale fiber production

Piezoelectric Polymer and Ceramic Ultrafine Fibers for Piezocomposite Films

This paper describes the process development and characterization of Poly(vinylidene fluoride) (PVDF) films and fiber mats and Zinc Oxide (ZnO) fibers as ingredients of a future piezo-composite film. The polymer system PVDF is electroactive and processed here by solution casting and annealing to form active films. Electrospinning of PVDF and Poly(vinyl alcohol)-Zincacetate precursor solutions were also under investigation to produce randomly oriented polymer and ceramic fiber mats, respectively. Effects of the electrospinning process and material parameters in the production of fiber mats were first studied by using Design of Experiments approach. Films produced by solution casting and fine fiber mats produced by electrospinning of PVDF were characterized regarding the manufacturability and distinct crystallization phases that determines the piezoelectric capability. The electrospun PVDF fibers as received indicated the insitu stretching effect that enables the required β-phase crystalline structure for piezoelectricity. The process flow for ZnO fibers that includes electrospinning of PVA-Zincacetate precursor fibers and calcinations was also investigated. Aside from typical fiber-like ZnO mats, ZnO whiskers and rods were also formed in this process flow

Piezoelectric polymer and ceramic ultrafine fibers for piezocomposite films

This paper describes the process development and characterization of Poly(vinylidene fluoride) (PVDF) films and fiber mats and Zinc Oxide (ZnO) fibers as ingredients of a future piezo-composite film. The polymer system PVDF is electroactive and processed here by solution casting and annealing to form active films. Electrospinning of PVDF and Poly(vinyl alcohol)-Zincacetate precursor solutions were also under investigation to produce randomly oriented polymer and ceramic fiber mats, respectively. Effects of the electrospinning process and material parameters in the production of fiber mats were first studied by using Design of Experiments approach. Films produced by solution casting and fine fiber mats produced by electrospinning of PVDF were characterized regarding the manufacturability and distinct crystallization phases that determines the piezoelectric capability. The electrospun PVDF fibers as received indicated the insitu stretching effect that enables the required β-phase crystalline structure for piezoelectricity. The process flow for ZnO fibers that includes electrospinning of PVA-Zincacetate precursor fibers and calcinations was also investigated. Aside from typical fiber-like ZnO mats, ZnO whiskers and rods were also formed in this process flow