Linear materials with nanofiber coating

This article deals with a possibility of a production of linear formations with nanofibers. Many authors try to achieve a production of single nanofibers or fiberbundles in which the nanofibers are more or less oriented. Higher orientation can provides needed properties as are strength, elasticity or suitability for other applications having a connection with a structure orientation. In the article the electrospinning process is described and in a short search some possibilities how to produce nanofiber structures with parallel orientation are shown, because in the process of the yarn production a higher orientation is strongly required. Further, the new electrospinning method and its modification are shown. This method is based on the discovery that it is possible to create Taylor cones not only from the tip of the capillary but also from a thin film of polymer solution. The modification of this method is based on the usage of linear collector, which simultaneously creates the career of nanofibers. In the article some examples of linear formations with nanofibers are shown and application possibilities are discussed. Methodes of nanofiber production Nanofibers are an interesting branch of nanomaterials. The name indicates that these are fibers with a diameter less than one micron. They have lots of advantageous properties for instance high specific area, high porosity, slenderness and many others. These properties can be used in various areas such as high efficiency filters, separation membranes, composite reinforcement, materials for tissue engineering and so on. Nanofibers can be produced by various techniques, which provide nanofibers with different properties. A method of a drawing is based on high drawing of filaments in process which is similar to dry spinning method. Another method is a technology of a nanofiber extrusion. This method provides meltblown fibers with an average size of 250 nm and a range between 25 and 400 nm . This method uses technology Island-In-The-Sea (fibers within fibers). The number of fibers within a fiber is about 1200. Last usable method is an electrospinnig process. The basic scheme is shown in the Figure 1. Figure 1: Description of electrospinning process. 1 – High voltage power supply, 2 – Syringe, 3 – Grouting point, 4 – Grounded collector, 5 – Jet of nanofibers This term indicates that the electrostatic forces are used for the spinning. These forces are created between electrodes which form so called spinning space. Usually the electrode with a positive charge is used for bringing of a spinning solution as well. The other electrode has a negative charge; in some cases it can be grounded. The electrospinning process is based on a drawing of an electrically charged jet from the spinning solution. In the jet source some cones are formed. The cones are created in the consequence of electrostatic forces and a surface tension of the spinning solution. The cones were named as Zeleny – Taylor cones. If the electric forces are more prominent than the surface tension, the liquid begins to form to cones with convex sides and rounded tips. If high voltage is increased a jet of liquid is emitted from the cones. The maximal half angle of a cone just before arising of the jet is 49,3°. The jet produces submicron fibers. Before their deposition on the collector 1 2 3 4