SEM and strength characteristics of acetylated sisal fibre

Journal of Materials Science Letters -     

Phospham—A stable phosphorus-rich flame retardant

Phospham is an iminophosphazene polymer of unusually high thermal stability. We have found that phospham imparts a substantial level of flame retardancy to nylon-4,6, a high-melting crystalline engineering thermoplastic. It did not appear to produce degradation of the polyamide in the processing temperature range. The flame retardant efficacy of phospham in nylon-4,6 was similar to that of stabilized red phosphorus, when compared on an equal phosphorus basis. In nylon-4,6, it did not display nitrogen–phosphorus synergism. Limited evidence from TGA suggested a condensed phase mode of action in nylon-4,6. Phospham showed orders-of-magnitude better hydrolytic stability than did ammonium polyphosphate, and did not produce detectable phosphine on processing as did red phosphorus.     

Effect of temperature on electrical behavior of flyash‐filled epoxy gradient composites

Functionally gradient composites of epoxy resin having different weight percentages of flyash were prepared under centrifugal force to obtain gradient in density, hardness, and electrical properties. Effect of temperature and frequency variation on dielectric constant (ε′), tan δ, and ac conductivity was determined by using a 4274 A Multi‐Frequency LCR meter. Electrical measurements were carried out in a temperature range from 40 to 180°C and in a frequency range from 1 to 100 kHz. It was observed that the dielectric constant and tan δ increased with increase in temperature and decreased with increase in frequency. The ac conductivity increases with increase in temperature and frequency. The increased weight percentage of flyash increased the compaction of flyash particle in the flyash‐rich phase of graded composites, which would have increased the dielectric constant (ε′), tan δ, and ac conductivity. Shore D hardness and density of the functionally gradient composites has also been determined and reported. A continuous increase in the hardness from 69 to 76 and density from 1.287 to 1.41 g/cc has been observed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1269–1276, 2006     

Investigation on gradient dielectric characteristics of bamboo (Dentroclamus strictus)

Dependence of dielectric constant (ε′) and dielectric dissipation factor (tan δ) on distance from outermost skin to the center of bamboo has been determined. Dielectric measurements have been done in the temperature range of 24–120°C and in the frequency range, 4–100 kHz. Gradient behavior in ε′ and tan δ has been found in bamboo. It has also been observed that ε′ and tan δ increase with increasing temperature and decrease with increasing frequency. Relaxation times have been calculated for the four samples at 80, 90, and 100°C temperatures, which show that relaxation time decreases with the increase of temperature because of the increased molecular mobility. A continuous increase in the hardness from center (48) to outer surface (70) and density from 0.45 to 0.80 g/cc has been observed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 380–386, 2006     

MultiSense: proportional-share for mechanically steerable sensor networks

Steerable sensors, such as pan-tilt-zoom cameras and weather radars, expose programmable actuators to applications, which steer them to dictate the type, quality, and quantity of data they collect. Applications with different goals steer these sensors in different directions. Although being expensive to deploy and maintain, existing steerable sensor networks allow only a single application to control them due to the slow speed of their mechanical actuators. To address the problem, we design MultiSense to enable fine-grained multiplexing by (1) exposing a virtual sensor to each application and (2) optimizing the time to context-switch between virtual sensors and satisfy requests. We implement MultiSense in Xen, a widely used virtualization platform, and explore how well proportional-share scheduling, along with extensions for state restoration, request batching and merging, and anticipatory scheduling, satisfies the unique requirements of steerable sensors. We present experiments for pan-tilt-zoom cameras and weather radars that show MultiSense efficiently isolates the performance of virtual sensors, allowing concurrent applications to satisfy conflicting goals. As one example, we enable a tracking application to photograph an object moving at nearly 3?mph every 23?ft along its trajectory at a distance of 300?ft, while supporting a security application that photographs a fixed point every 3?s.     

Aqueous lubricating properties of charged (ABC) and neutral (ABA) triblock copolymer chains

Application of charged polymer chains as additives for lubricating neutral surfaces in aqueous environment, especially via polymer physisorption, is generally impeded by the electrostatic repulsion between adjacent polymers on the surface. In this study, we have investigated the adsorption and aqueous lubricating properties of an amphiphilic triblock copolymer, comprised of a neutral poly(ethylene glycol) (PEG) block, a hydrophobic poly(2-methoxyethyl acrylate) (PMEA) block, and a charged poly(methacrylic acid) (PMAA) block, namely PEG-b-PMEA-b-PMAA. After adsorption onto a nonpolar hydrophobic surface from aqueous solution, an equal and homogeneous mixture of neutral PEG and charged PMAA chains is formed on the surface, with an adsorbed polymer mass comparable to its fully neutral counterpart, PEG-b-PMEA-b-PEG. The lubricity of PEG-b-PMEA-b-PMAA showed significant improvement compared to fully charged polymer chains, e.g. poly(acrylic acid)-block-poly(2-methoxyethyl acrylate) (PAA-b-PMEA), which is attributed to dilution of charged moieties on the surface and subsequent improvement of the lubricating film stability.     

Investigation of water vapor permeability and antimicrobial property of zinc oxide nanoparticles‐loaded chitosan‐based edible film

This study is focused on the investigation of moisture uptake properties of chitosan films. The GAB isotherm model is found to fit well to the experimental moisture uptake data obtained at 10, 25, and 37°C. The water vapor permeability is found to increase with temperature. The use of plasticizer enhances the water vapor permeability. Finally, the films have been loaded with ZnO nanoparticles and characterized by X‐ray diffraction, differential scanning calorimetry, surface plasma resonance, and scanning electron microscopic analyses. The crystal size as determined using Scherrer's equation is found to be around 15 nm. The films have shown excellent antibacterial action against the model bacterium Escherichia coli. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Characterisation of anthocyanins from Garcinia indica Choisy

The present study deals with isolation and characterisation of anthocyanins present in Garcinia indica Choisy (popularly known as kokum), which is a potential source of a natural food colourant. The kokum was found to contain a very high concentration of anthocyanins (2.4 g/100 g of kokum fruit), compared to other natural sources. Acid hydrolysis ascertained that this anthocyanin consisted of a single aglycone, i.e., cyanidin. A comparison of saponified and unsaponified fraction indicated that the pigment was not acylated. HPLC, mass and NMR spectroscopy analyses confirmed that the pigment essentially contains two anthocyanins, which were identified as cyanidin 3-glucoside and cyanidin 3-sambubioside.