Vijayalakshmi Rao

Studies on the compatibility and specific interaction in cellulose acetate hydrogen phthalate (CAP) and poly methyl methacrylate (PMMA) blend

Abstract Compatibility of cellulose acetate hydrogen phthalate (CAP) and poly methyl methacrylate (PMMA) has been investigated by solution viscometric, ultrasonic and differential scanning calorimetric (DSC) methods. From viscosity measurements, Krigbaum and Wall polymer–polymer interaction parameter is evaluated. Ultrasonic velocity and adiabatic compressibilites versus blend composition are plotted, and found to be linear. T g values are calculated using Gordon–Taylor and Fox equations. The results obtained reveal that CAP forms a miscible blend with PMMA in the entire composition range. Compatibility may be due to the formation of hydrogen bond between the carbonyl group of PMMA and the free hydroxyl group of CAP. Compatibility is further predicted from dielectric measurements.

Studies of dielectric relaxation and a.c. conductivity in cellulose acetate hydrogen phthalate–poly(methyl methacrylate) blends

Abstract Dielectric constant, dielectric loss and a.c. conductivity of polyblends of cellulose acetate hydrogen phthalate(CAP) and poly(methyl methacrylate) (PMMA) of different compositions have been measured in the temperature range 300–430 K and in the frequency range 50–100 kHz. Variations in dielectric constant with temperature of the blends exhibit unique behavior, different from the component polymers. In the blends, the dielectric loss as a function of temperature displays a single peak corresponding to the glass transition temperature ( T g ), in the region between the T g values of the pure polymers. The T g values observed agree well with those values obtained from DSC. Dielectric studies show that CAP forms miscible blends with PMMA. AC conductivity values are calculated from dielectric data and the conduction mechanism is discussed.

Mechanical Properties and Swelling Behavior of Cross-Linked Natural Rubber/Chitosan Blends

Abstract This article discusses properties such as surface hardness, solvent uptake, cross-link density, diffusion coefficient, and tensile properties of vulcanized natural rubber (NR)/chitosan (CS) blends. Dicumyl peroxide was selected as a cross-linking agent. In the case of tensile properties, peroxide vulcanized blends show higher tensile strength and hardness (Shore A) than the unvulcanized blend. The effect of thermal aging on mechanical properties of vulcanized NR/CS blends was also examined. The solvent-resistance properties of these vulcanized blends were investigated by the equilibrium swelling method using benzene as solvent. The impact of weight fraction of chitosan on the transport properties of vulcanized blend was also analyzed. The improved solvent resistance for peroxide vulcanized blends proved the formation of cross-links in the rubber phase. The blends showed reduced swelling rate due to the tortuosity of the path and the reduced transport area in blended samples.

The Emergence of New Ion Tract Applications

Abstract The recent years have brought a renaissance of interest in ion tracks, for the sake of novel applications. This paper summarizes some of the newly emerging possibilities, and the strategies that have been initiated. Only a few applications that are based on latent tracks have emerged since then, such as the exploitation of phase transitions, chemical changes, the enhanced free volume along latent tracks, or their capability to trap diffusing penetrants. For contrast, etched tracks in both polymer foils and SiO 2 layers appear to have a much greater application potential. Compact rods and tubules as well as dispersed nanosized matter can be embedded within the etched tracks to form the base of various applications. Some of them are summarized, and a few examples are described in detail.

Characterization of Natural Rubber Latex/Chitosan Blends

Abstract In an attempt to prepare novel biodegradable materials, blends of natural rubber latex/chitosan (NR/CS) with different compositions have been prepared by solution casting followed by compression. The blends were characterized by thermogravimetry, Fourier transform-infrared spectroscopy (FT-IR), X-ray diffraction, and scanning electron microscopy (SEM) techniques. The effect of thermal stability on the percentage of natural rubber latex (NR) in the blend was studied. The percentage of bound rubber content and fraction of rubber dissolved in benzene was determined. Better interfacial adhesion between chitosan and natural rubber is achieved in the blend NR95 CS5. This is reflected in the IR spectrum also. The water absorption behavior of the blends has also been studied. X-ray diffraction study shows a decrease in crystallinity in natural rubber with addition of chitosan.

Adsorption of Methylene Blue onto Natural Rubber/Chitosan Blends

Adsorption experiments were carried out for the removal of methylene blue (MB) cationic dye from its aqueous solution using natural rubber (NR)/chitosan (CS) blends as adsorbent. The results showed that chitosan has less adsorption capacity and introducing a small amount of chitosan could improve the adsorption capacity of natural rubber. A reduction in adsorption capacity is also observed for the vulcanized and maleic anhydride (MA) treated blends. Different isotherm models were applied to the experimental data in order to understand the mechanism of adsorption. It was found that a Langmuir equation is more suitable for the description of adsorption isotherm.

Etched ion track polymer membranes for sustained drug delivery

Abstract The method of track etching has been successfully used for the production of polymer membranes with capillary pores. In the present paper, micropore membranes have been prepared by swift heavy ion irradiation of polycarbonate (PC). PC films were irradiated with ions of gold, silicon and oxygen of varying energies and fluence. The ion tracks thus obtained were etched chemically for various time intervals to get pores and these etched films were used as membranes for the drug release. Ciprofloxacine hydrochloride was used as model drug for the release studies. The drug content was estimated spectrophotometrically. Pore size and thus the drug release is dependent on the etching conditions, ions used, their energy and fluence. Sustained drug release has been observed in these membranes. The films can be selected for practical utilization by optimizing the irradiation and etching conditions. These films can be used as transdermal patches after medical treatment.

Effect of PTSA on the electrical conductivity of I2 doped poly-4-vinyl pyridine (P4VP)

Abstract The effect of P -toluene sulfonic acid (PTSA) on the DC conductivity of iodine doped poly(4vinylpyridine) (P4VP) thick films for various dopant concentrations has been reported. P -toluene sulfonic acid is used as a counter ion and found to be a good stabilizer and plasticizer. DC conductivity of these films has been studied as a function of temperature and conduction mechanisms have been discussed. The stability in DC conductivity of the complex at high temperature is mainly due to reabsorption of I 2 by PTSA

Miscible blends of cellulose acetate hydrogen phthalate and poly(vinyl pyrollidone) characterization by viscometry, ultrasound, and DSC

Miscibility characteristics of cellulose acetate hydrogen phthalate (CAP) and poly(vinyl pyrollidone) (PVP) have been investigated by solution viscometric, ultrasonic, and differential scanning calorimetric (DSC) methods. From viscosity measurements, Krigbaum and Wall polymer–polymer interaction parameter Δb was evaluated. Ultrasonic velocity and adiabatic compressibility have been plotted versus blend composition and are found to be linear. Variation of Tg with composition follows Gordon–Taylor equation. Tg values have also been calculated from the Fox equation. The results obtained reveal that CAP forms a miscible blend with PVP in the entire composition range. Compatibility may be due to the formation of hydrogen bonding between the carbonyl group of PVP and the free-hydroxyl group of CAP. Compatibility has also been confirmed from dielectric measurements.

Production parameters for the formation of metallic nanotubules in etched tracks

The formation of conducting nanotubules in etched tracks is reported in literature since about a decade. However, up to now precise production recipes are scarce. For this sake we present here a systematic study on some important factors that influence the formation of metallic nanotubules. In the case of chemical deposition, the first question to be answered is the choice of the activation technique to produce the required activation centers. Both the time of activation and the time of subsequent chemical deposition are crucial parameters in this connection. Finally, the maximum temperature is determined up to which thermal stability of the etched tracks and of the tubules therein is given. This study should allow one to predict better the efficiency of conducting nanotubule formation.