Grafting of N,N′‐methylenebisacrylamide onto cellulose using Co(III)‐acetylacetonate complex in aqueous medium

The grafting of N,N′‐methylenebisacrylamide (N,N′‐MBA) onto cellulose is carried out using the cobaltacetylacetonate complex (Co(acac)₃) under nitrogen atmosphere at 40°C. The rate of graft copolymerization has been studied as a function of [N,N′‐MBA], [Co(acac)₃], and temperature. The activation energy of grafting is found to be 156.0 k J mol⁻¹ within the temperature range of 30–60°C. The effect of perchloric acid, methanol, and surfactants on graft yield has also been studied and results are suitably explained. The higher efficiency of the metal chelate in initiation of graft copolymerization has been assumed due to the coordination of the π electrons of the N,N′‐MBA with the metal chelate, which facilitated the formation of the radicals through homolytic cleavage of metal–oxygen bond of the cobalt acetylacetonate complex. On the basis of the results, a suitable kinetic scheme for graft copolymerization is presented and rate expression is derived. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 906–912, 2000     

Effects of Thermal and Cryogenic Conditionings on Flexural Behavior of Thermally Shocked Cu-Al2O3 Micro and NanoComposites

This investigation has used flexural test to explore the effects of thermal treatments, i.e., high-temperature and cryogenic environments on the mechanical property of Al₂O₃ particulate-reinforced Cu metal matrix micro and nanocomposites in ex-situ and in-situ conditions. Cu-5 vol. pct Al₂O₃ micro (10 μm)- and nanocomposites (<50 nm) fabricated by powder metallurgy route were subjected to up-thermal shock cycle [193 K to 353 K (?80 °C to 80 °C)] and down-thermal shock cycle [353 K to 193 K (from 80 °C to ?80 °C)] for different time periods followed by 3-point bend test. One batch of specimens (micro and nanocomposites) was conditioned at 353 K and 193 K (80 °C and ?80 °C) separately followed by 3-point flexural test. High-temperature flexural test was performed at 373 K and 523 K (80 °C and 250 °C) on the micro and nanocomposites. All the fractured samples obtained after various thermal treatments were studied under scanning electron microscope (SEM). The development of thermal stresses quite often results in concentration of residual stresses at the particle/matrix interface eventually weakening it. Enhancement of flexural strength was recorded for down- as well as for up-thermal shock in microcomposites. The high-temperature flexural strengths of micro and nanocomposites are lower than those at ambient temperature. The amelioration and declination in mechanical properties as a consequence of thermal shock, thermal conditioning, and high-temperature flexural testing have been discussed in the light of fractography.     

Ionic liquid mediated application of nano zinc oxide on cotton fabric for multi-functional properties

In this work, nano zinc oxide (nano-ZnO) was applied onto cotton fabric by exhaustion method using an ionic liquid (IL), 1-butyl 3-methyl imidazolium chloride [BMIM][Cl], to improve its uptake and fixation. Effect of temperature on the exhaustion of nano-ZnO in the presence of ionic liquid was investigated. A spectrophotometric method was established to determine the concentration of nano-ZnO in the exhausted bath. Treated cotton fabrics were characterized using Fourier transform infrared, scanning electron microscope, atomic absorption spectroscopy, X-ray diffraction, Thermo gravimetric analysis and UV spectrophotometry. Washing durability test using the AATCC 61-2003 method demonstrated that the amount of nano-ZnO retained in the cotton substrate was sufficient enough to exhibit 50+ UV protection and 99% inhibition against the tested pathogenic micro-organisms. A plausible mechanism for better exhaustion of nano-ZnO on cotton fabric has been proposed on the basis of ionic liquid driven swelling property of the cotton polymer.     

Ion‐conductivity study and anomalous diffusion analysis of plasticized gelatin films

In this article, we report a study on ion conduction in gelatin films with different concentrations of glycerol as a plasticizer; these films might be a candidate for electrolyte materials in solid polymer batteries. The ion conductivity was appreciable, showing a maximum of about 9.14 × 10^?3 S/m at room temperature without the addition of any ionic salt. Analysis of the impedance measurements was done with a model based on material properties instead of the usual equivalent circuit formalism, where circuit elements are difficult to interpret. Generalized calculus was used to model the anomalous diffusion in the system. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3018–3024, 2013     

Thermal and electrical behavior of silver chloride/polyaniline nanocomposite synthesized in aqueous medium using hydrogen peroxide

Nanocomposites of AgCl/PANI were synthesized by chemical polymerization/precipitation in aqueous HCl solution using both aniline monomer and AgNO₃ precursors in different molar ratio in PVP. Silver ions interact with PVP which restrict the bulk growth of AgCl and keep it in nanosized. During synthesis, AgCl NPs got entrapped in PANI chains through inter-chain hydrogen bonding. TGA studies showed complete decomposition of polymer chains occurred at 30–40 °C higher temperature than PANI alone. DSC studies indicate higher thermal stability of the composite, which is due to more heat flow for decomposition of polymer chains indicating compact packing of polymer matrix with AgCl NPs having large surface area to volume ratio. The TEM image showed spherical NPs were randomly dispersed in a polymer matrix and from XRD data crystalline nature of composite was seen. In FT-IR spectrum strong absorption band of a carbonyl stretching group due to PVP indicates its presence on nanoparticle surface in composite. Thin films of nanocomposite were spin casted on ITO coated glass surface. Electrical conductance was calculated from I–V data which was found to be in the range of 10^?2–10^?7 S cm^?1 depending on the concentration of NPs in it. These composites may find applications in solar cells as semiconductor material and for designing multiarray sensors for quality interpretation of beverages on the basis of their conductance changes using soft computing techniques.     

The effects of sorbates on the ensilage of chopped whole-plant maize and lucerne

The incorporation of (a) sorbic acid (0.18 and 0.90 g kg^?1, fresh weight basis) and potassium sorbate (0.90 g kg^?1) with chopped lucerne, and (b) sorbic acid (0.90 g kg^?1) and potassium sorbate (0.90 g kg^?1) with chopped maize (whole-plant) at the time of ensiling, led to a reduction in the surface spoilage associated with the ensilage of these two forages. Use of sorbic acid (0.90 g kg^?1) and potassium sorbate (0.90 g kg^?1) led to (a) a reduction of volatile nitrogen (VN), higher levels of residual water-soluble carbohydrates (WSC) in lucerne silage and more aerobically stable lucerne silage and (b) a reduction in weight loss, population of yeasts and moulds, and VN, higher levels of WSC in maize silage and more aerobically stable maize silage when compared to the untreated forages or forages treated with sorbic acid and potssium sorbate at 0.045 and 0.18 g kg^?1 (fresh weight basis), respectively.     

Effect of complexing agent on the chemically deposited ZnS thin film

Zinc sulfide (ZnS) thin films have been deposited onto fluorine doped tin oxide and microscopic glass substrates from an aqueous alkaline reaction by chemical bath deposition. The effect of concentrations of hydrazine hydrate (HyH) (complexing agent) on the deposit is studied. X-ray analysis confirm the growth of nanocrystalline ZnS thin films with reflections (111), (220) and (311) correspond to cubic crystalline phase. TEM results support the growth of cubic ZnS layers. The energy band gap was successfully tailored from 2.77 to 3.80 eV. Photoluminescence study indicates a strong band-edge emission with some defect like vacancies. It was also noticed that HyH plays an important role on the nucleation. The remarkable improvement in the growth rate of ZnS thin films have been observed upon increasing the contents of HyH. Nearly stoichiometric ZnS layer was obtained upon annealing prepared with 2.5 M HyH. The crystallinity was found to be increased upon annealing the layers. The ideality factor for the ZnS layers prepared with 0 and 1.0 M HyH were obtained?~1.71 and 1.24, respectively. The capacitance–voltage plots behave according to Schottky–Mott theory. The doping concentrations?~10¹⁷ and 10¹⁸ cm^?3 were calculated for the layers deposited with 0 and 1.0 M HyH, respectively.     

Sorption kinetics and diffusion of alkanes into tetrafluoroethylene/propylene copolymer membranes

Sorption kinetics and diffusion of hexane, heptane, octane, nonane, decane, cyclohexane, and 2,2,4-trimethylpentane through tetrafluoroethylene/propylene copolymer membranes were studied using the gravimetric sorption method at 30, 45, and 60°C. Coefficients of diffusion were calculated from Fick's equation. From these data, the permeability coefficients were obtained. Analytical solutions of Fick's relations were used to estimate the liquid concentration profiles into the polymeric membranes at different times. The profiles of liquid concentrations were also simulated for the polymer–solvent systems using the numerical simulation method. Activation parameters for diffusion and sorption were evaluated and these results are discussed in terms of the molecular sizes and geometries of liquids (i.e., shape) as well as temperature. The diffusion coefficients follow a systematic decrease with increasing size of the penetrant molecules. The activation energies i.e., E_D values, increase with increasing size of n-alkanes. © 1996 John Wiley & Sons, Inc.