An investigation on the electrospinning process and the effect of its process variables on orientation, crystallinity, microstructure and mechanical properties of the. mation during the electrospinning process. Four critical .. for the inverse relationship between the solution viscosity and temperature (as shown in Fig. ). Electrospinning is a process that produces continuous In the electrospinning process, the positive electrode .. relationship of electrospun bioabsorbable.
Response surface methodology has been employed for the modelling and optimization of the electrospinning process, using a Box-Behnken design. The investigation, based on a second order polynomial model, has been focused on the analysis of the effect of both process voltage, tip-to-collector distance, flow rate and material sulfonation degree variables on the mean fiber diameter.
The final model has been verified by a series of statistical tests on the residuals and validated by a comparison procedure of samples at different sulfonation degrees, realized according to optimized conditions, for the production of homogeneous thin nanofibers. Introduction Nanofibers are an interesting and versatile class of one-dimensional nanomaterials, with diameters ranging from tenths to hundreds of nanometers, which have been recognized as promising due to their outstanding properties in terms of high porosity, excellent pore interconnectivity, small diameters and high surface-to-volume ratio.
Among the different nanofiber manufacturing technologies, electrostatic spinning, or electrospinning, represents the easiest, most promising [ 1 ] and versatile method for the generation of aligned or randomly distributed nanofibers of a rich variety of different materials, such as synthetic and natural polymers [ 2 ], composites [ 3 ], ceramics [ 4 ] and metals [ 5 ]. Electrospinning allows the production of nanofibers by applying a high electric field capable to overcome the surface tension of a polymeric solution.
When the voltage reaches a threshold value the solution is deformed and produces an electrically charged jet that travels towards a grounded collector. During this phase the jet undergoes a whipping process in which it is stretched and, thanks to the evaporation of the solvent, produces a solid fiber.
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The intrinsicly-complex nature of the process does not always lead to satisfactory results from the applications of theoretical models, which can have limited descriptive capability, and prevent a full understanding of the results from a one factor analysis. Response surface methodology RSM is a collection of statistical and mathematical techniques capable to allow the construction of an approximating model for the description of the relationship between a response and a set of predictor variables, on the basis of empirical data obtained by an appropriate experimental design.
With RSM it is possible to carry out a simultaneous investigation of the effect of the single variables and their mutual interaction, with the possibility to define quantitatively optimized conditions to apply to a given process.
Sulfonated polyether ether ketone sPEEK is a sulfonated derivate of the polyaryl ether ketone family, which has been recognized as a promising candidate for the replacement of Nafion for proton exchange membranes PEMs due to its good conductivity and thermal stability.
A 23 factorial design was performed to determine the influence of the following factors: Factorial design enables the analysis of the mathematical relationship between the chosen factors and the response with a minimum number of experiments.
The factor having the most significant impact on the size of beaded fibers and beads was the solution viscosity, while the voltage had the greatest influence on the bead-free fiber diameter. The interactions between the studied factors were also analyzed.
It was found that the presented method can be used for the design of an optimal and cost-effective electrospinning process, allowing the desired product to be obtained with expected features. The reason for this is the wide range of diameters possible i.
"Process - Structure – Property Relationships of Electrospun Nano Fiber" by Sudhakar Jagannathan
In addition, the technique is rather easy to employ and cost-efficient [ 3 — 4 ]. Currently, by modifying the experimental setup and controlling the properties of the polymer solutions, it is possible to obtain fibers of different structure: Because of the variety of obtained structures that are possible, electrospun nanofibers find applications in well-established technologies, as well as in new fields of scientific and industrial interest.
They are considered to be potentially useful in areas such as nanoelectronics, medicine e. Current research on the electrospinning method is concentrated on the conditions of the process [ 7 — 8 ], fiber characteristics and their potential application. As of today, there are several studies regarding the influence of process conditions as they relate to the properties of the obtained product [ 358 — 10 ]. Not only do they concern the values but also the change of process parameters such as: What should be emphasized is that electrospinning is a complex process with a considerable number of factors that may influence the final product properties.
Hence, establishing a complete description of all the occurring phenomena poses a real challenge. One of the most interesting works in this area is the one by Yuya et al. According to this study, the higher the concentration of polyvinylpyrrolidone PVP ethanolic solution higher solution viscosity used, the thicker the fibers.
In addition, both the type of solvent its physicochemical properties and the water content in the solvent turned out to be influential in terms of the fiber surface morphology.
It was also concluded that methanol and ethanol were best suited for electrospinning of PVP, in contrast to water and dimethylformamide DMFwhich prevented the polymer from spinning. What is more, the higher the water content of the solvent, the less uniform fibrous mats were obtained.
Finally, the effect of humidity was also examined: Another interesting work on the impact of process conditions on the surface morphology of nanofibers is the one by Deitzel et al. This work focuses on the influence of two process variables: In this study it was observed that the increase in electrical voltage changed the shape of the electrospinning jet.
In addition, it was shown that the voltage was strongly correlated with the formation of beads, which were recognized by authors as defects. An increase in electrical voltage caused an increase in the density of beads in the obtained polymer mats.