| Abstract [eng] |
Nanotechnology is no longer a novelty in the modern context. Electrospinning is a versatile and effective nano-micro fibre formation technique, which produces nanofibres with excellent mechanical properties, large surface area and high porosity. Polysaccharides as biopolymers are of great interest to scientists and industry representatives for the possibility to change synthetic polymers to the native polymers. These interests in polysaccharides-based polymers are influenced by positive properties such as biocompatibility, biodegradability, nontoxicity and economic price. The formed fibres with polysaccharides are as well promising due to their wide application possibilities. The excellent properties make them very suitable in the biomedical field. It can be stated that from all the polysaccharides, starch is one of the most abundant and lowest price polysaccharides. On the basis of various research results provided in different literature sources, it can be stated that the fibre formation of pure starch is possible but in general difficult to electrospun. In order to improve the electrospinning process of the starch as polymer, it can be modified, i.e., its chemical structure is modified, which allows the formation of the fibre with this polysaccharide. Starch can be blended with synthetic polymers that have excellent spinning properties as well. Starch was the main objective of this dissertation. In order to achieve the improvement of electrospinnability and formed nano-micro size fibres, starch was cationically modified and mixed with synthetic polymer. In this work the fibre web was electrospun by using the NanospiderTM (Germany) electrospinning equipment. The fibres that were manufactured in this equipment used two different kinds of rotating electrode: cylindrical and electrode with the tines. The rotating electrode is partially immersed in a tray with polymer solution, towards the upper electrode, which is attached to the collection part. Scanning Electron Microscopy (SEM) with SEM-FEI Quanta 200 (The Netherlands) was used to observe and identify the morphology and structure of nonwoven material from nano-microfibres. A small section of the nano-microfibre mat was used in SEM with the use to determine the morphology of nano-microfibres. Lucia 5.0 software was utilized to measure the diameter of nano-microfibres and calculate the average diameters of the observed fibres. In this doctoral dissertation, fibres from mixtures of poly(vinyl alcohol) PVA and natural starch solutions were formed by electrospinning method, when the potato starch content in PVA spinning solution (1, 3 and 5%). The influence of a small amount of ethanol (1, 3, 5 %) on the process of electric spinning and on the structure and morphology of the formed fibres was also analyzed. A series of tests was performed with PVA and cationic starch KOEK at a weight ratio of 75/25, 50/50 and 35/65 in the spinning solution. The influence of different concentrations of the formed fibres and the influence of low ethanol content (3, 6 and 9 %) on the morphology of the fibres structure and the electrospinning process were analyzed. The dissertation proves that using electrospinning method, it is possible to form fibres from PVA and potato starch spinning solutions. The influence of ethanol on the electric spinning process and the morphology and structure of the formed filaments was investigated. The most suitable concentration of spinning solutions from PVA/KOEK was determined when the mass ratio was 75/25 and the most suitable rotating electrode type for the electrospinning process was selected and determined. In this work it was proved that it is possible to form fibres from PVA solution with 50 % and 65 % KOEK. |
