The aim of this paper was the study of the rheological instability (thixotropy and/or antithixotropy) of normal potato starch (NPS) pastes depending on their concentration (2-5%) and degree of pasting. Flow curves with hysteresis loops, apparent viscosity at constant shear rate and in-shear structural recovery tests were carried out. Granule size profiles, the pasting characteristic of corresponding starch suspensions and the transmittance of the pastes, the molecular weights and polydispersity of granular starch and its pastes prepared at 80, 95 and 121°C were also studied. The degree of pasting was dependent on the temperature and the concentration and influenced strongly the rheological behavior of the pastes. All pastes belonged to the non-Newtonian liquids thinned by shear and were rheologically unstable to the various extent. Thixotropic properties were connected to the size and the number of the starch granules in the pastes as well as depended on the measuring method used. In the 2 and 3% samples pasted at 80°C the swelling of the granules prevailed their destruction (thixotropy was observed). In the other samples the destruction predominated the swelling (antithixotropy observed).

No abstract

No abstract

Due to their unique properties, hydrogels can be used in many areas of life and science. The main purpose of this work was to present the possibility of using hydrogels as a kind of fire retardant material itself and as a medium in fire retardant materials used, among others, as the extinguishing agents for fires and the suppression agents for the self-ignition of coal in mines (where their low viscosity and high ability to penetration of the protected material is used), protective layers in fabrics and the so-called robot skin (most often applied in the layer-by-layer system), filling in the fire retardant window panels (mostly hybrid hydrogels or hydrogel copolymers are used) and protective emulsions of the wooden elements used in construction and furniture joinery (mainly in combination with silicate and phosphate derivatives). In the presented applications, hydrogels can be used alone, e.g. due to the large water capacity and at the same time the possibility of dilution, or in combination with fire retardants, what very often allows for the multiplication of the extinguishing or fire retardant effect. Due to the multitude of available studies and the speed of scientific development, this review is focused mainly on publications written after 2015.

No abstract