Browsing by Author "Militky, Jiri"

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    Effect of surface modification and knife penetration angle on the Quasi-Static Knife Penetration Resistance of para-aramid fabrics
    (2019-04-03) Javaid, Muhammad Usman; Militky, Jiri; Wiener, Jakub; Jabbar, Abdul; Salacova, Jana; Umair, Muhammad
    The focus of this paper is to describe the effect of change in surface friction of single layer para-aramid (TwaronA (R)) square woven fabric and change in knife penetration angle on its Quasi-Static Knife Penetration Resistance (QSKPR). The surface friction of fabric was changed by depositing SiO2 on its surface by using water glass as a precursor. Six different knife penetration angles (0 degrees, 22.5 degrees, 45 degrees, 67.5 degrees, 90 degrees and 135 degrees) were selected. Untreated and treated fabric samples were compared for change in QSKPR. It was observed that the deposition of SiO2 on the surface of TwaronA (R) fabric increased the surface friction which resulted in the increase in QSKPR. The response of fabric against QSKPR changed from partial yarn cutting to individual yarn cutting in fewer steps and load was distributed to a larger area due to decrease in yarn slippage. The change in penetration angle changed the distance, knife cutting edge travelled to cut each next yarn(s) and when this distance increased, the QSKPR was reduced. The post-penetration image analysis of damaged fibres showed that the load distribution among warp and weft yarns was complementary and change in penetration angles changed the distribution of stabbing load among the warp and weft yarns. When yarns with higher tensile strength and less slippage were loaded, the fabric showed highest resistance to penetration. A QSKPR prediction model was also proposed at the end.
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    Flame resistance behavior of cotton fabrics coated with bilayer assemblies of ammonium polyphosphate and casein
    (2019-03-01) Faheem, Sajid; Baheti, Vijay; Tunak, Maros; Wiener, Jakub; Militky, Jiri
    This research report discusses the intumescent flame resistance and physiological comfort of cotton fabrics after being coated with bilayer assemblies of different concentrations of ammonium polyphosphate (APP) and casein solutions. The flame resistance was investigated using horizontal flame propagation, cone calorimetry and thermo-gravimetric analysis, whereas physiological comfort was estimated in terms of air permeability, water vapor permeability and stiffness testing. From cone calorimetry results, the coated fabrics showed very slow combustion kinetics as the concentration of casein or APP was increased. Although, higher concentration of casein was found to produce higher char residue, but the physiological comfort properties were deteriorated beyond 5wt% casein. The images of burnt samples confirmed the formation of a distinct intumescence layer of char residue and it was also validated from the measurements of thermal conductivity of char residues. In this way, the presented work showed that the casein could perform number of functions such as catalyzed dehydration, accelerated charring and intumescent char formation in APP based intumescent systems.