Preparation of crosslinked chitosan by electron beam irradiation in the presence of CCl4

In this article, we report the synthesis of crosslinked chitosan using 8 MeV electron beam (EB) irradiation in the presence of carbon tetrachloride. The crosslinked chitosan is characterized by dissolution, Fourier transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning colorimetry (DSC), and nanoindentation studies. The insolubility of irradiated films in acetic acid indicates that chitosan has undergone crosslinking reaction. FTIR analysis also confirms the crosslinked structure of chitosan. Mechanical properties such as elastic modulus and hardness are calculated from the nanoindentation data. Modulus and hardness of chitosan increase with increase in the irradiation dose due to the increase in the crosslinking. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

On the summation of certain legendre series

Summary The purpose of this paper is to find some recurrence relations for sums of infinite series of the form P _l ⁿ (cos)t ^l+m/(l+m). This is achieved by transforming the sums into integrals and then using the recurrence relations for these integrals.On leave from the Department of Mathematics, Kurukshetra University, Kurukshetra, India.     

Synthesis and application of polycarbosilane supported manganese ions as catalyst in mannich reaction

Polycarbosilane (PCS) with highly crosslinked structure and high surface area was synthesized by the polycondensation reaction between trimethoxyvinylsilane and trichloromethylsilane. The reaction was conducted in the presence of sodium metal. Manganese ion was supported on PCS. The immobilization of transition metal ions to polymer support leads to a number of advantages over homogeneous catalyst, viz easy product recovery, increased selectivity, etc. The catalytic activity of PCS supported manganese ion was studied by considering three‐component Mannich reaction. Reaction with diverse sets of aldehydes, amines, and ketones was examined. PCS‐supported manganese ion catalyst has been prepared for the first time and used successfully in Mannich reaction. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

The effect of microstructure on the rate-dependent stress-strain behavior of poly(urethane urea) elastomers

Segmented poly(urethane urea) materials (PUUs) exhibit versatile mechanical properties and have drawn great interest due to their potential for protection against projectile impacts and blast loadings. To optimize the performance of PUUs for various high rate applications, specific features of their mechanical behavior have to be suitably tailored by altering the microstructure. Hence the micromechanisms governing the mechanical behavior must be identified, understood and leveraged. In this study, the effects of varying microstructure on the rate-dependent mechanical behavior were examined for select PUU materials. As expected, increasing the hard segment content increased the stiffness and the flow stress levels. Interestingly, it was observed that promoting phase mixing among the hard and soft segment domains of the PUU material greatly enhanced its rate-dependent stiffening and strain hardening behavior. These insights can help design PUUs for articles that manifest improved protective abilities under impact, while maintaining their flexibility during normal use. The potential applications for such materials are extensive, including face masks and goggles, which require excellent folding/un-folding capabilities, while also providing superior impact resistance.     

A spectroscopic approach for structural characterization of polypropylene/clay nanocomposite

This study focuses on the degree of dispersion and structural development of organomodified MMT clay (OMMT) during processing of polypropylene clay nanocomposites using both conventional and nonconventional characterization techniques. PP‐g‐MA and Cloisite 15A were melt blended with three different grades of PP separately in a micro‐twin screw compounder at selected screw speed and temperature. The clay was modified with fluorescent dyes and the adsorbed dye content in the clay gallery was estimated by using UV‐spectrophotometric method. The effects of residence time and molecular weight of the PP matrix on the clay dispersion were studied. The extent of dispersion and exfoliation of the clay in polymer matrix determined from the torque versus time data obtained from microcompounder. It was further supported by XRD, SEM, TEM, and DSC analysis. Offline dielectric and fluorescence spectrophotometric studies were also carried out. Changes in dielectric constant and dielectric loss with both frequency and temperature yielded quantitative information about the extent of clay exfoliation and intercalation in the polymer matrix. It was observed that with an increase in MFI (decrease in molecular weight) and mixing time, the extent of clay dispersion and exfoliation were also improved due to easy diffusion of polymer chains inside clay gallery. POLYM. COMPOS., 31:2007–2016, 2010. © 2010 Society of Plastics Engineers     

Comments on “surface waves in fibre-reinforced anisotropic elastic media” by Sengupta and Nath [Sādhanā 26: 363–370 (2001)]

In the paper under discussion, the problem of surface waves in fibrereinforced anisotropic elastic media has been studied. The authors express the plane strain displacement components in terms of two scalar potentials to decouple the plane motion into P and SV waves. In the present note, we show that, for wave propagation in fibre-reinforced anisotropic media, this decoupling cannot be achieved by the introduction of the displacement potentials. In fact, the expressions for the displacement potentials used by the authors do not satisfy one of the equations of motion. Consequently, most of the equations and results of the subject paper are either irrelevant or incorrect     

Metal Immiscibility Route to Synthesis of Ultrathin Carbides,Borides, and Nitrides

Ultrathin ceramic coatings are of high interest as protective coatings from aviation to biomedical applications. Here, a generic approach of making scalable ultrathin transition metal‐carbide/boride/nitride using immiscibility of two metals is demonstrated. Ultrathin tantalum carbide, nitride, and boride are grown using chemical vapor deposition by heating a tantalum‐copper bilayer with corresponding precursor (C₂H₂, B powder, and NH₃). The ultrathin crystals are found on the copper surface (opposite of the metal–metal junction). A detailed microscopy analysis followed by density functional theory based calculation demonstrates the migration mechanism, where Ta atoms prefer to stay in clusters in the Cu matrix. These ultrathin materials have good interface attachment with Cu, improving the scratch resistance and oxidation resistance of Cu. This metal–metal immiscibility system can be extended to other metals to synthesize metal carbide, boride, and nitride coatings.     

Degradation of 2,4-dichlorophenol in aqueous solution by sono-Fenton method

This study presents the results of the Sono-Fenton process for the degradation of 2,4-dichlorophenol (DCP). The influential parameters such as H₂O₂, Fe²⁺ and pH for the Sono-Fenton process were investigated. Sono-Fenton method was found to be the best one for degradation efficiency of DCP when compared with that of the Fenton process. The optimum concentrations for the degradation of DCP using conventional Fenton’s method were found to be 20 mg/L of Fe²⁺ and 580 mg/L of H₂O₂ at pH 2.5. In the case of Sono-Fenton, the optimal concentrations were found to be 10 mg/L of Fe²⁺ and 400 mg/L of H₂O₂ at pH 2.5. Sono-Fenton method resulted in the reduction of required Fe²⁺ concentration (50%) and H₂O₂ concentration (31%). In addition, this method could be applicable even at pH 5.0 and a degradation efficiency of DCP was 77.6%. Kinetic studies for the degradation of DCP proved that the degradation of DCP tends to follow pseudo first order reaction and the rate constant was found to be 7 × 10⁻⁴ min⁻¹.     

Assessment of bioremediation possibilities of technical grade hexachlorocyclohexane (tech-HCH) contaminated soils

Hexachlorocyclohexane (HCH) is a broad spectrum insecticide still used in some of the developing countries, though developed countries have banned or curtailed its use. Even in those countries where the use of t-HCH has been discontinued for a number of years, the problem of residues of all isomers of t-HCH remains because of its high persistence. These insecticides in the soil disturb the delicate equilibrium between microorganisms and their environment. Few reports on the degradation of t-HCH isomers in soil are present in literature, and very little information is available on the effect of these t-HCH isomers on soil microflora. In the present study, an attempt has been made to see the microbial diversity in the uncontaminated soils and the effect of application of t-HCH on the soil microflora. The soil was spiked with t-HCH and incubated, at regular time intervals the soil samples were analyzed for microbial diversity as well as t-HCH isomers residues. The results show that at higher concentrations of t-HCH, microbial populations were inhibited and the inhibited populations did not reappear even after prolonged incubation. Potential t-HCH degrading cultures were isolated and subjected to further acclimation in order to enhance their degradation capacity. The results are presented and discussed in this paper.