A method of manufacturing hydrogel coatings designed to increase the hydrophilicity of polyurethanes (PU) is presented. Coatings were obtained from polyvinylpyrrolidone (PVP) by free radical polymerisation. The authors proposed a mechanism of a two-step grafting - crosslinking process and investigated the influence of reagent concentration on the coating’s physical properties - hydrogel ratio (HG) and equilibrium swelling ratio (ESR). A surface analysis of freeze-dried coatings using scanning electron microscopy (SEM) showed a highly porous structure. The presented technology can be used to produce biocompatible surfaces with limited protein and cell adhesive properties and can be applied in fabrication of number of biomedical devices, e.g. catheters, vascular grafts and heart prosthesis.
The paper discusses possible applications of the percolation theory in analysis of the microstructure images of polycrystalline materials.
Until now, practical use of this theory in metallographic studies has been an almost unprecedented practice. Observation of structures so
intricate with the help of this tool is far from the current field of its application. Due to the complexity of the problem itself, modern
computer programmes related with the image processing and analysis have been used. To enable practical implementation of the task
previously established, an original software has been created. Based on cluster analysis, it is used for the determination of percolation
phenomena in the examined materials. For comparative testing, two two-phase materials composed of phases of the same type (ADI
matrix and duplex stainless steel) were chosen. Both materials have an austenitic - ferritic structure. The result of metallographic image
analysis using a proprietary PERKOLACJA.EXE computer programme was the determination of the content of individual phases within
the examined area and of the number of clusters formed by these phases. The outcome of the study is statistical information, which
explains and helps in better understanding of the planar images and real spatial arrangement of the examined material structure. The results
obtained are expected to assist future determination of the effect that the internal structure of two-phase materials may have on a
relationship between the spatial structure and mechanical properties.