Nanocoatings consisting of ammonium polyphosphate (APP), sodium montmorillonite (MMT), and vinyltrimethoxysilane (VTMS) were prepared via self-assembly and in situ sol-gel techniques and applied onto cotton fabrics to achieve both flame retardancy and hydrophobicity. The impacts of APP concentration on the hydrophobicity and fire resistance of the coated fabrics were investigated. Attenuated total reflectance Fourier transform infrared (ATR-FTIR) characterization results verified the hydrolysis-condensation reaction of VTMS and the formation of Si-O-Si network structure. X-ray diffraction (XRD) proved the formation of a layered structure based on MMT nanosheets in the coatings. Both vertical flame test (VFT), limiting oxygen index (LOI), thermogravimetric analysis (TGA) and microscale combustion calorimeter (MCC) characterization were conducted to evaluate the flame retardancy, thermostability and heat release behavior of the coated cotton fabrics, respectively. The results suggested that a higher concentration of APP is beneficial for both hydrophobicity and flame retardancy of the coated substrates. Overall, our research provides a facile and very effective approach to prepare flame retardant and hydrophobic multifunctional coating for cotton fabric and other substrates.

Intumescent flame retardant and hydrophobic coatings, consisting of sodium montmorillonite (MMT), am moniu m d ihy dro gen ph os pha te ( ADP), an d methyltrimethoxysilane (MTMS), were prepared via in situ sol-gel and self-assembly techniques to acquire multifunctional cotton fabrics. The impact of MTMS concentration on hydrophobicity, fire resistance, thermal stability, and heat release behavior of the coated fabrics was investigated. A Si-O-Si network structure was generated via the hydrolysis-condensation reaction of MTMS, induced by the catalysis of ADP. After treated by the coating with 2.0 wt.% of MTMS, the cotton fabric with a total uptake of 22.7 wt.% achieved appreciable flame retardancy and hydrophobicity, as well as satisfactory thermal stability and heat release behaviors. Overall, this research provides a facile and effective approach to prepare flame retardant and hydrophobic cotton fabrics.

The thermal rearrangement of polyimides of ortho‐positioned functional group membranes improves the gas permselectivity properties of the polyimide precursor. For this experiment, HAB‐6FDA polyimide was synthesized from 3,3 dihydroxy‐4,4‐diamino‐biphenyl (HAB) and 2,2‐bis‐(3,4‐dicarboxyphenyl) hexafluoropropane dianhydride (6FDA) by chemical imidization. A sample was modified from a pure polymer to silica nanoparticle composition. Furthermore, a modification was carried out by thermal rearrangement reaction at temperatures of 350, 400, and 450°C. The thermal property of these membrane films was characterized by differential scanning calorimetry (DSC), FTIR, opacity experiment, and free volume analysis. Permeability decreases with an increase in the kinetic diameter of gasses, which is normal behavior for glassy polymers. The composition of silica nanoparticles slightly changes the permeability in the polyimide. The combined effect of silica nanoparticles and thermal rearrangement of the HAB‐6FDA membrane has shown an excellent performance. The thermal rearrangement with nanocomposite shows a significant impact on a larger effect on permeation for lighter gases, that is, H2, CO2, and O2, compared with N2 and CH4. Particularly for H2/CH4 gas pair, it lies over Robeson's 2008 upper bound limit, which fits the composition in the novel class for the gas separation membranes.

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Knowledge of residual chlorine concentration at various locations in drinking water distribution system is essential final check to the quality of water supplied to the consumers. This paper presents a methodology to find out the residual chlorine concentration at various locations in simple branch network by integrating the hydraulic and water quality model using first-order chlorine decay equation with booster chlorination nodes for intermittent water supply. The explicit equations are developed to compute the residual chlorine in network with a long distribution pipe line at critical nodes. These equations are applicable to Indian conditions where intermittent water supply is the most common system of water supply. It is observed that in intermittent water supply, the residual chlorine at farthest node is sensitive to water supply hours and travelling time of chlorine. Thus, the travelling time of chlorine can be considered to justify the requirement of booster chlorination for intermittent water supply.