RESUMEN
Textile ballistic shields are the basis of protection against bullets and fragments with low kinetic energy. They are usually made of para-aramid fabrics or unidirectional structure (UD) sheets of ultra-high molecular weight polyethylene (UHMWPE). The aim of the research presented in the article was to obtain ballistic packages made of embroidered structures and to compare their ballistic properties with those of woven structures in terms of deformation of the standardized ballistic substrate after impact with a 9 mm bullet at a velocity of 380 ± 3 m/s. Using the tailored fiber placement method, embroidered structures were fabricated by embroidering two sets of para-aramid threads at an angle of 90°. As the woven structures, the use of para-aramid fabric made of the same yarn and with a surface weight comparable to that of embroidered structures was adopted. Ballistic packages consisted of 26 layers in five variants, also taking into account the hybrid arrangement of woven and embroidered layers. Ballistic tests have shown that the best ballistic properties have hybrid packages made by folding 13 woven and then 13 embroidered layers, where the maximum deformation of the plasticine substrate is below 23 mm. The conducted research confirmed that embroidered structures in appropriate combination with woven structures can significantly improve the ballistic properties of textile packages.
RESUMEN
In this work, we propose a novel method for the preparation of polypyrrole (PPy) layers on textile fabrics using a reactive inkjet printing technique with direct freezing of inks under varying temperature up to -16 °C. It was found that the surface resistance of PPy layers on polypropylene (PP) fabric, used as a standard support, linearly decreased from 6335 Ω/sq. to 792 Ω/sq. with the decrease of polymerization temperature from 23 °C to 0 °C. The lowest surface resistance (584 Ω/sq.) of PPy layer was obtained at -12 °C. The spectroscopic studies showed that the degree of the PPy oxidation as well as its conformation is practically independent of the polymerization temperature. Thus, observed tendences in electrical conductivity were assigned to change in PPy layer morphology, as it is significantly influenced by the reaction temperature: the lower the polymerization temperature the smoother the surface of PPy layer. The as-coated PPy layers on PP textile substrates were further assembled as the electrodes in symmetric all-solid-state supercapacitor devices to access their electrochemical performance. The electrochemical results demonstrate that the symmetric supercapacitor device made with the PPy prepared at -12 °C, showed the highest specific capacitance of 72.3 F/g at a current density of 0.6 A/g, and delivers an energy density of 6.12 Wh/kg with a corresponding power density of 139 W/kg.
RESUMEN
In the article a description of the behaviour of metallic layers created in the process of physical vacuum deposition on a composite textile substrates during their cyclical bending process is presented. Either the results of experimental research or the theoretical considerations of changes in the structure resistance as a function of the number of fatigue cycles are presented. It was confirmed mathematically that at the beginning of the bending process, in the case of a small number of bends, single cracks appear on the surface of the layer. After exceeding a certain number of bends, the nature of defects on the surface of the layer changes and the dominating mechanism of changes is the widening and elongation of already existing cracks. It has been confirmed mathematically that changes in resistance in these cases depend respectively on the number of bending cycles and next on quadratic value of number of cycles. A correspondence between the mathematical description and experimental results was obtained.
RESUMEN
This work is a follow-up study for a recently-proposed 3D radiochromic gel dosimeter that contains a tetrazolium salt and a physical gel matrix made of poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (Pluronic F-127). Several tetrazolium salts were examined in this work, including tetrazolium violet, blue tetrazolium chloride, nitro blue tetrazolium chloride (NBT), tetranitro blue tetrazolium chloride (tNBT) and thiazolyl blue tetrazolium bromide (TBTB). The salt-containing gel dosimeters were compared with the first Pluronic gel composition that contained 2,3,5-triphenyltetrazolium chloride (TTC) as the radiation-sensitive component (dose sensitivity of 0.0023 (Gy cm)-1). The Pluronic gels with NBT and tNBT outperformed the other gels, including the TTC-containing gel, with respect to their dose sensitivity and low dose-response. The NBT gels were found to have better stability over time than tNBT gels. Sensitization of the gels to ionizing radiation was examined by addition of tert-butyl alcohol and sodium formate. The best composition was 0.0818% NBT (1 mM), 25% Pluronic F-127 and 0.136 × 10-2% sodium formate. This gel dosimeter was insensitive to changes in dose rate for photons of different energies. The mean dose sensitivity amounted to 0.0047 ± 0.1 × 10-4 (Gy cm)-1. A diversion in the dose-response was observed for the gel irradiated with electrons. Additional characteristics of the NBT gel were a linear-dose range and a dynamic-dose range between <1 and ⩾150 Gy and a dose threshold of <1 Gy. The dose distribution registered for the NBT-Pluronic gel was stable after irradiation for over 7 d with no visible diffusion of the irradiated part, which is analogous to the original TTC-Pluronic gel.