Melt viscoelastic properties of peroxide cured polypropylene‐ethylene octene copolymer thermoplastic vulcanizates

The dynamic viscoelastic properties of uncrosslinked and dynamically crosslinked blends of polypropylene (PP) and ethylene octene copolymer (EOC) were investigated in the melt state to study the mechanism of reinforcement, influence of particle size, and kinetics of modulus recovery. Dynamic vulcanization was performed by coagent assisted peroxide crosslinking system. Addition of peroxide in PP/EOC blend involves two major competing reactions: crosslinking in EOC and degradation of PP by β chain‐scission. In this article, morphological and melt rheological properties of the TPVs were studied with special reference to the effect of mixing protocol. Three different mixing techniques were investigated. They are: (i) conventional or preblending method—melt mixing of PP and EOC followed by dynamic vulcanization (ii) phase mixing method—curative master batch of EOC added on the molten PP (iii) split addition of PP—preblending method followed by addition of half part of PP (dilution procedure). The type of mixing protocol has a significant influence on the rheological behavior. Rheological properties have been evaluated at the processing temperature (180°C) in a Rubber Process Analyzer (RPA 2000). A variety of rheological observations such as Payne effect, modulus recovery and shear rate sensitivity were studied by carrying out frequency and strain amplitude sweeps. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers     

Novel methyl cellulose‐grafted‐acrylamide/gelatin microspheres for controlled release of nifedipine

Naturally available carbohydrate polymers such as methylcellulose (MC) and gelatin (Ge) have been widely studied in the previous literature for controlled release (CR) applications. In this study, methyl cellulose‐g‐acrylamide/gelatin (MC‐g‐AAm/Ge) microspheres were prepared by water‐in‐oil (W/O) emulsion method and crosslinked with glutaraldehyde to encapsulate with nifedipine (NFD), an antihypertensive drug. The microspheres prepared were characterized by differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and laser particle size analyzer. DSC thermograms of NFD‐loaded AAm‐MC/Gel microspheres confirmed the molecular level distribution of NFD in the matrix. SEM indicated the formation of spherical particles. Swelling experiments supported the drug diffusion characteristics and release data of the matrices. Cumulative release data were analyzed using an empirical equation to understand the nature of transport of drug through the matrices. Controlled release characteristics of the matrices for NFD were investigated in pH 7.4 media. Drug was released in a controlled manner up to 12 h. Particle size and size distribution of the microspheres as studied by laser light diffraction particle size analyzer indicated their sizes to be around 120 μm. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Visually observed mold and moldy odor versus quantitatively measured microbial exposure in homes

The main study objective was to compare different methods for assessing mold exposure in conjunction with an epidemiologic study on the development of children's asthma. Homes of 184 children were assessed for mold by visual observations and dust sampling at child's age 1 (Year 1). Similar assessment supplemented with air sampling was conducted in Year 7. Samples were analyzed for endotoxin, (1-3)-β-D-glucan, and fungal spores. The Mold Specific Quantitative Polymerase Chain Reaction assay was used to analyze 36 mold species in dust samples, and the Environmental Relative Moldiness Index (ERMI) was calculated. Homes were categorized based on three criteria: 1) visible mold damage, 2) moldy odor, and 3) ERMI. Even for homes where families had not moved, Year 7 endotoxin and (1-3)-β-d-glucan exposures were significantly higher than those in Year 1 (p < 0.001), whereas no difference was seen for ERMI (p = 0.78). Microbial concentrations were not consistently associated with visible mold damage categories, but were consistently higher in homes with moldy odor and in homes that had high ERMI. Low correlations between results in air and dust samples indicate different types or durations of potential microbial exposures from dust vs. air. Future analysis will indicate which, if any, of the assessment methods is associated with the development of asthma.     

Visible light photocatalytic water splitting for hydrogen production from N-TiO2 rice grain shaped electrospun nanostructures

We report on the visible light-driven hydrogen production from splitting of water molecules by nitrogen-doped TiO₂ (N-TiO₂) with a rice grain-like nanostructure morphology. The N-TiO₂ nanostructures are prepared using sol-gel and electrospinning methods followed by post-annealing of the composite nanofibers. The nanostructures are characterized by microscopy and spectroscopy. First order rate constants for the visible light-assisted photocatalysis in the degradation of methylene blue (MB) dye are found to be 0.2 × 10⁻³ and 1.8 × 10⁻³ min⁻¹ for TiO₂ and N-TiO₂ (5 wt% of nitrogen), respectively. The N-TiO₂ utilized in water splitting experiments and evaluated hydrogen (H₂) of 28 and 2 μmol/h for N-TiO₂ and TiO₂, respectively. The improvement may be attributed due to the N-doping and higher surface area as ∼70 m²/g.     

Microneedle assisted iontophoretic transdermal delivery of prochlorperazine edisylate

This paper investigates the microneedle (MN) mediated in vitro transdermal iontophoretic delivery of prochlorperazine edisylate (PE) across dermatomed human skin. The Dermaroller? induced microchannels were visualized using methylene blue staining and scanning electron microscopy. In vitro skin permeation studies were performed using vertical static Franz diffusion cells. Iontophoretic protocols involved application of direct current at a density of 0.4 mA/cm(2) using Ag as an anode and Ag/AgCl as a cathode. The effect of PE concentration (20, 50 and 100 mg/mL), number of passes of microneedles (0, 5, 10 and 20) on both iontophoretic and passive delivery of PE was studied. The Dermarollertm was found to successfully breach the skin barrier and a linear relationship (r(2) = 0.99) was observed between the number of passes of the Dermaroller? and the number of microchannels created. Passive transdermal flux of PE (0.060 ± 0.003 μg/cm(2)/h) at 50 mg/mL donor PE concentration) was low and increased (4.15 ± 0.57 μg/cm(2)/h) with the application of direct current. Application of iontophoresis in conjunction with microneedle pre-treatment resulted in enhanced flux (4.90 ± 0.39 μg/cm(2)/h at 50 mg/mL donor PE concentration) of PE. The projected transdermal PE flux indicates that a 9 cm(2) patch could deliver PE in a sufficient amount to maintain therapeutic levels of the drug. In conclusion, microneedles when used in conjunction with iontophoresis significantly enhanced the transdermal delivery of PE and it may be feasible to develop an iontophoretic transdermal patch that could be integrated with MN.     

Preparation of diamond like carbon thin films above room temperature and their properties

Diamond like carbon (DLC) thin films were deposited on p-type silicon (p-Si), quartz and ITO substrates by microwave (MW) surface-wave plasma (SWP) chemical vapor deposition (CVD) at different substrate temperatures (RT ∼ 300 °C). Argon (Ar: 200 sccm) was used as carrier gas while acetylene (C₂H₂: 20 sccm) and nitrogen (N: 5 sccm) were used as plasma source. Analytical methods such as X-ray photoelectron spectroscopy (XPS), FT-IR and UV–visible spectroscopy were employed to investigate the structural and optical properties of the DLC thin films respectively. FT-IR spectra show the structural modification of the DLC thin films with substrate temperatures showing the distinct peak around 3350 cm^− 1 wave number; which may corresponds to the sp² C–H bond. Tauc optical gap and film thickness both decreased with increasing substrate temperature. The peaks of XPS core level C 1 s spectra of the DLC thin films shifted towards lower binding energy with substrate temperature. We also got the small photoconductivity action of the film deposited at 300 °C on ITO substrate.     

A MODEL FOR THE SOLID CIRCULATION RATE IN A RECIRCULATING FLUIDIZED BED

The present work is an experimental study on the solid circulation rate in a recirculating fluidized bed and mathematical modeling of the same based on the experimental results and existing literature. The effects of particle size, spacing between the draft tube bottom and distribution plate, inventory of solids, and superficial gas velocity on the solid circulation rate are studied experimentally on a semicircular cold model recirculating fluidized bed. A mathematical model is developed for the solid circulation rate incorporating the effect of the various operating and design parameters. The model is based on the present experimental work and data available in the literature for the same kind of reactors. Dimensional analysis and nonlinear regression models are used to develop the model. The final model equation is a non linear relationship between the different operating and design variables. The model equation gives good results for the same kind of systems and can be used with reasonable accuracy for a wide range of operating parameters.     

Degradation of Toxaphene by Zero-Valent Iron and Bimetallic Substrates

The pesticide, toxaphene, is a major environmental concern and has been reported to be harmful, especially via skin contact, ingestion, or inhalation. Although now banned, it persists in nature. The results of this research showed that toxaphene in an aqueous solution was degraded by dechlorination when contacted with Fe0 and bimetallic substrates. This degradation displayed a power-law relationship with a decrease of toxaphene concentration over time. Toxaphene contacted with Fe0 produced a degradation rate value, ?kTox [ln(h)]?1, of 0.088 for a solution-to-mass ratio of 4:1 and 0.113 for a 2:1 ratio. Doubling the initial concentration of toxaphene for a volume-to-mass ratio of 4:1 decreased the degradation rate and resulted in a ?kTox value of 0.061. Bimetallic substrates including nickel-plated Fe0 and copper-plated Fe0 had degradation values of 0.219 and 0.245, respectively. A chloride mass balance indicated that nearly all of the toxaphene in the solution had been dechlorinated; as the chloride concentration in the solution increased over time, the toxaphene concentration decreased. The increase of chloride ions in the solution displayed a logarithmic relationship over time for all of the substrates contacted with toxaphene.     

Solid-state synthesis and characterization of LiCoO2 and LiNi y Co1−y solid solutions

Solid solutions of compositions LiNi _y Co_1−y O₂ (y = 0.0, 0.1 and 0.2) were prepared by solid-state fusion synthesis from carbonate precursors. Material characterization was carried out using XRD. Formation mechanisms of the products are discussed in the light of TG/DTA results. Nickel-containing compositions gave higher discharge capacities and smaller hystereses in their charge-discharge profiles which make them more attractive than pristine LiCoO₂ as cathode materials in high-energy lithium cells. The lower loss in capacity per cycle for cells with unsubstituted LiCoO₂, as determined from cycling studies up to 25 cycles, makes it more suitable than the substituted ones for long cycle-life cells with low capacity fade.