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1.
Influence of temperature and pressure during PGSS[sup]TM micronization and storage time on degree of crystallinity and crystal forms of monostearate and tristearate
Zoran Mandžuka, Željko Knez, 2008, original scientific article

Abstract: For controlling the degree of crystallinity and crystal form during particle formation using supercritical fluids, knowledge of pressure influence on solid-liquid-gas (S-L-G) equilibrium and solubility data of the system is crucial. S-L-G equilibrium data were determined in pressure range from 50 to 600 bar for systems monostearate/CO2 and tristearate/CO2 using a high-pressure view cell. Results showed a temperature minimum for both systems.The solubilities of CO2 in liquid glycerides were high: maximum solubilities, which were determined at temperatures 70 and 90 °C and pressure range from 50 to 450 bar, were from 50 to 90 mol%. Physical characteristics of micronized monostearate and tristearate samples were studied in detail after micronization and after 3 months of storage at 20 °C.
Keywords: chemical processing, high pressure technology, supercritical fluids, micronization, fine particles, Particles from Gas Saturated Solution, degree of crystallinity
Published: 31.05.2012; Views: 2070; Downloads: 24
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2.
The influence of structural properties on the dye diffusion and dyeability of PA 6 fibres
Simona Strnad, Slava Jeler, Karin Stana-Kleinschek, Tatjana Kreže, 2003, original scientific article

Abstract: The relationships were investigated between the structural and dyeing properties of different structurally modified PA 6 fibers. PA 6 monofilament yarn samples were applied having different crystalline degrees and different content of alpha, respectively gamma crystalline modification. The diffusion coefficients of two different acid dyes were determined together with the content of dyestuff absorbed (under specific conditions) by fiber samples. In order to estimate colorimetry method from the viewpoint of polymer structural change detection, the colors of the dyed PA 6 samples were determined (L*, a*,b*, C*, h coordinates) and the color differences (L*, a*, b*, C*, H*, E*) were calculated between untreated standard and structurally modified samples. The dyeability of PA 6 fibers depended mainly on the way in which crystallinity had been achieved, i.e. on the materialćs history. Different crystalline modifications caused different sorption properties and fiber dyeability. Smaller increases (app 20%) of crystallinity degree caused a decrease in diffusion coefficients. Contrary to expectations, the significant increase of crystallinity degree (app 50%) had an influence on the increase ofdyeability, presumably owing to the formation of larger empty spaces in the structure. The results achieved by colorimetry were in good correlation with dye absorption measurements. The colorimetry of dyed fiber samples was sensitive enough to detect even small differences in the quantities of absorbed dyestuff.
Keywords: textiles, PA 6 fibres, dyeing, dyeability, fibre structure, crystallinity, chemical modification
Published: 01.06.2012; Views: 1426; Downloads: 12
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