Study On Preparation And Its Mechanism Of PHBV Nanofibers

Electrospinning is a process by which sub-micron and nanoscale polymer fibers can be produced using an electrostatically driven jet of polymer solution (or polymer melt). The small fiber diameters and the porous structure of electrospun fabrics result in a high specific area that is beneficial in a wide variety of applications. Proposed uses of electrospun fibers include filters, membranes, wound dressings, vascular grafts and tissue engineering scaffolds. There are two necks for this technology: detail understanding of the mechanism and the application of electrospun nanofibers.It was established that the essential mechanism of electrospinning was three kinds of instabilities: two axisymmetric modes and one non-axisymmetric mode. The first axisymmetric mode can be associated with the classical Rayleigh instability, which is dominated by surface tension. In addition, however, there are two electrically driven modes, which were referred to as'conducting' modes because at high electric field they are primarily sensitive to the fluid conductivity and insensitive to surface tension. In the axisymmetric modes, the centerline of the jet remains straight but the radius of the jet is modulated. However, in the whipping instability, the radius of the jet is constant but the centerline is modulated. Experimental results revealed that the two axisymmetric modes were responsible for the formation of beaded nanofibers and whipping instability for preparation of superfine fibers.Influence of the variables, including operating conditions (applied voltage, solution feeding rate and the collecting distance), solution properties (viscosity, conductivity and surface tension) and charge density carried by the moving jet, on jet various instabilities and formation of different nanofiber morphologies was investigated.The lotus blossom is the symbol of cleanliness in Asiatic religion: its leaves unfold dry and in contaminable from the mud (Lotus Effect). It was shown that superhydrophobic surface could be obtained through a simple method called electrospinning, even if the material was inherently hydrophilic. This kind of technology holds the ability to form micro and nanoscaled roughness at the same time, both of which attribute to high contact angle of a water droplet on the resulting mat. The reason for thesuperhydrophobicity was thought to be that air trapped between the droplet and the nanoscaled protrusions at the mat surface minimized the contact area. The method might successfully be used to prepare superhydrophobic surfaces from a wide variety of materials.左伟伟 (Material Science and Engineering) Supervised by: Prof. 朱美芳...