Analysis of Diffraction Line Profile from Silk Fibers Using Various Distribution Functions

Microstructural parameters of varieties of silk fibers, like C.nichi, Pure Mysore Silk (PMS), Hosa Mysore (HM) and Nistari, have been determined by Fourier method of Warren using wide angle X-ray scattering (WAXS) data. Exponential, Lognormal, Reinhold functions for the column length distributions have been used for the determination of microstructural parameters. The goodness of the fit and the consistency of the results suggest the exponential distribution gives much better results in the analysis of fiber diffraction even though lognormal distribution has been widely used to estimate the similar stacking faults in metal oxide compounds. Estimated micro-structural parameters have been compared with parameters of other silk fibers like, Hosa Mysore, Pure Mysore Silk (PMS) and Nistari as a comparison of their molecular maps shows a wide contrast between them.     

Physical and thermal properties of 8 MeV electron beam irradiated HPMC polymer films

Microstructural modification in hydroxypropyl methylcellulose (HPMC) polymer films induced by electron irradiation is studied. Irradiation was performed in air at room temperature using a 8 MeV electron accelerator at doses of 25, 50, 75 and 100 kGy. Irradiation can be used to crosslink or degrade the desired component or to fix the polymer morphology. Changes in microstructural parameters, crystallinity and thermal properties in virgin and irradiated HPMC films have been studied using wide angle X-ray scattering data and differential scanning calorimetry. The heat of fusion and the degree of crystallinity are found to be highest for unirradiated HPMC and the crystallite size is larger in virgin HPMC films.     

Crystallite size and shape in Twaron fibers heat treated at different temperatures using WAXS

We have determined the crystallite size of Twaron fibers heat treated at various temperatures by analyzing the wide angle X‐ray scattering (WAXS) data employing a profile analysis technique developed by us. This study indicates that the differential change of size with temperature is less than 1% of the mean value along both (110) and (200) directions. Hence, these fibers are thermally stable and thermal aging is negligible. We have also observed that the lattice strain variation with temperature is negligible. These studies demonstrate the thermal stability of fibers in terms of the changes in the microcrystalline parameters. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4910–2916, 2006     

Correction: Thermo-electric power and humidity sensing studies of the polypyrrole-tantalum pentoxide composites

Journal of Materials Science: Materials in Electronics -     

Spectroscopic and thermal studies of 8 MeV electron beam irradiated HPMC films

Radiation-induced changes in hydroxypropyl methylcellulose (HPMC) films under electron irradiation were investigated and correlated with dose. Polymer samples were irradiated in air at room temperature by an electron beam accelerator in the range of 0-100 kGy. Various properties of the irradiated films were studied using a Ultraviolet-Visible spectrophotometer and Fourier transform infrared spectroscopy and thermogravimetric analysis. Electron irradiation was found to induce changes in the physical, chemical and thermal properties, depending on the irradiation dose.     

Variation of lexan polycarbonate properties by electron beam

The modifications in microstructural, optical, and photoluminescence properties of the Lexan polycarbonate (bisphenol‐A‐polycarbonate) films exposed to different electron doses have been studied using UV–vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), positron annihilation lifetime spectroscopy, photoluminescence spectroscopy, and scanning electron microscopy (SEM). The obtained UV–vis spectroscopy results showed decrease in optical energy gap, optical activation energy, and increase in number of carbon atoms per cluster with increase in electron dose. The chemical changes in electron irradiated polymers due to chain scission and reconstruction have been observed from FTIR spectroscopy. The correlation of positron lifetime study with optical measurement is obtained, and electron irradiation‐induced microstructural modifications within the polymer is understood. SEM result shows the degradation of Lexan polymer after electron irradiation. The mechanical properties and average molecular weight of Lexan decrease after irradiation, whereas average number of chain scissions per original polymer molecule increases. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Strain–tensor components,crystallite shape,and their effects on crystalline structure in silk I

By using the X‐ray powder data obtained from Bombyx mori silk fibroin in silk I modification, we have estimated the strains by using profiles of several (hkl) reflections observed in the fibroin. For this purpose, we have used line profile simulation and matching with the experimental, on the basis of a paracrystalline one‐dimensional Hosemann's model proposed earlier. The shape of the crystallite and size along different directions in the fibroin have also been estimated and presented here. From these results, the strain tensor has been computed by using the approach given by Wilke and Martis. The effect of these strains on the molecular arrangement within the crystal structure and the nature of changes in the chain within the unit cell which participates in inducing the intrinsic strain during the formation of the fiber (silkII) are reported here. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3045–3053, 2004     

Polymerization of acrylonitrile initiated by Ce(IV)-sucrose redox system: A kinetic study

The polymerization of acrylonitrile (M), initiated by the free radicals formed in situ in the Ce (IV)-sucrose redox system, was studied in aqueous sulfuric acid medium under nitrogen atmosphere in the temperature range of 30–60°C. The rate of polymerization is proportional to [M]^1.0, [R]^0.76, [Ce(IV)]^0.8, and [H⁺]^−0.46. The rate of Ceric ion disappearance and the rate of polymerization R_p have been measured. The effects of some water–miscible organic solvents, surfactants, ionic strength, and complexing agents on the rate of polymerization were investigated. The temperature-dependence of the rate was studied and the activation parameters were computed using the Arrhenius and Eyring plots. A mechanism consistent with the experimental data, involving Ce(IV)-sucrose complex formation, which generates free radicals, is suggested. The chain termination step of the polymerization reaction was determined. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Microstructural parameters in electron‐irradiated hydroxypropyl methylcellulose films using X‐ray line profile analysis

The changes in microstructural parameters in hydroxypropyl methylcellulose (HPMC) polymer films irradiated with 8 MeV electron beam have been studied using wide‐angle X‐ray scattering (WAXS) method. The crystal imperfection parameters such as crystal size <N>, lattice strain (g in %), and enthalpy (α^*) have been determined by line profile analysis (LPA) using Fourier method of Warren. Exponential, Lognormal, and Reinhold functions for the column length distributions have been used for the determination of these parameters. The goodness of the fit and the consistency of these results suggest that the exponential distribution gives much better results, even though lognormal distribution has been widely used to estimate the similar stacking faults in metal oxide compounds. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008