Search

Agar–gelatin-based co-hydrogels were prepared with different compositions of the agar and the gelatin fractions. The intermolecular hydrogen bonding was higher in the co-hydrogels as compared to the gelatin hydrogel. Swelling studies indicated diffusion-mediated swelling. The electrical stability of the co-hydrogels was higher as compared to the gelatin hydrogel. Though the firmness of the co-hydrogels was higher, Weichert model of viscoelasticity indicated that the inherent mechanical stability of the gelatin hydrogel was superior. The release of ciprofloxacin hydrochloride was predominately Fickian diffusion-mediated. In gist, the co-hydrogels can be tried as polymeric constructs for controlled drug delivery applications. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Food Science (John Wiley & Sons, Inc.) is the property of John Wiley & Sons, Inc. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

ABSTRACT The discovery of rare earth based phosphors in 1960s started a new era of luminescence. In comparison with sulfide-based phosphors, strontium aluminates received worldwide acceptance because of their chemical stability and good luminescent properties. The SrAl xO y:Eu2+,Dy3+ phosphors excited by UV or visible light emit phosphorescence in the blue-green region after the excitation source has been removed, and the phosphorescence last for more than 15 h. The major disadvantage of SrAl xO y:Eu2+,Dy3+ phosphors is that they are prone to hydrolysis and their luminescent properties gradually deteriorate. The dispersion of these phosphors in a waterproof polymer matrix is an alternative method reported for retaining their luminescent properties. The review extensively deals with strontium aluminate based luminescent materials, the mechanism of luminescence, their synthesis techniques, and different mixing procedures to prepare polymer/strontium aluminate composites. Different methods to improve the dispersion of the strontium aluminate in the polymer matrix are also outlined. [ABSTRACT FROM AUTHOR]

Optimization of rotor speed based on stretching, efficiency, and viscous heating in nonintermeshing internal batch mixer has been investigated using polymer melt. A practical optimization technique was followed for optimization. Four different rotor speeds were used and characterized numerically with viscous dissipation and stretching. The heat distribution between rotor edge and mixer wall was calculated. Stretching experienced by the fluid was analyzed and the result was verified experimentally using particle tracking method. Exponential increase of energy dissipation between the rotor edge and the barrel at higher speed highlighted the importance of choosing the thermal properties of the polymer to avoid thermal degradation. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 [ABSTRACT FROM AUTHOR]

Polyethylene terephthalate (PET) with nano SiO2 and ZnO were prepared using a haake batch mixer. The thermal properties of PET and its nanocomposites were investigated by differential scanning calorimetry (DSC). The crystallization process of the nanocomposites samples was found to be different than that of the neat PET. The presence of SiO2 and ZnO shows a considerable effect on the melting behaviour & crystallinity of the composites. The activation energies of the nanocomposites were evaluated using Kissinger's method. The Half crystallization time of the nanocomposites were evaluated using Avrami's method. The morphology of the composites was characterized by Scanning Electron Microscopy (SEM). The dispersion and interfacial interaction between SiO2/ ZnO and the polymer matrix were also investigated by SEM. [ABSTRACT FROM AUTHOR]

Alumina-supported chromium oxide and binary mixed oxide catalysts of the form Cr–M oxide/γ-Al2O3 (where M is Ni, Co, Mo, W, Ho, La, Li, Cs or Bi) were found to catalyze the oxidative dehydrogenation of propane at 300-450 °C. The basic characters of the metals were found to determine partly the selectivity to propylene. Cr–Mo/γ-Al2O3 proved to be the most promising. It exhibited a propylene yield of 10.3% at 450 °C. The connections between the selectivity and reducibility of the catalyst were explored. TPR results showed that addition of molybdenum to chromium increased the temperature of reduction maxima. Thus the selectivity to propylene was improved by a decrease in the tendency of the catalyst to undergo a redox cycle. Further, an X-ray photoelectron spectroscopy study conducted on a sample of the catalysts showed that the basicity of the catalysts increased with increase in molybdenum. Catalysts with appropriate Cr/Mo ratios exhibited lower selectivity to over-oxidation product than those containing either chromium or molybdenum alone. [ABSTRACT FROM AUTHOR]

The activities of metal oxide catalysts in propane oxidative dehydrogenation to propene have been studied. The catalysts are M/γ-Al2O3 (where M is an oxide of Cr, Mn, Zr, Ni, Ba, Y, Dy, Tb, Yb, Ce, Tm, Ho or Pr). Both transition metal oxides (TMO) and rare-earth metal oxides (REO) are found to catalyze the reaction at 350-450 °C, 1 atm and a feed rate of 75 cm3/min of a mixture of C3H8, O2 and He in a molar ratio of 4:1:10. Among the catalysts, Cr-Al-O is found to exhibit the best performance. The selectivity to propene is 41.1% at 350 °C while it is 54.1% at 450 °C. Dy-Al-O has the highest C3H6 selectivity among the REO. At 450 °C, the other catalysts show C3H6 selectivity ranging from 16.2 to 37.7%. In general TMO show higher C3H6 selectivity than REO, which, however, show higher C2H4 selectivity. An attempt is made to correlate propane conversion and selectivity to C3H6 with metal-oxygen bond strength in the catalysts. For the TMO a linear correlation is found between the standard aqueous reduction potential of the metal cation of the respective catalyst and its selectivity to propane at 11% conversion. No such correlation has been found in the case of REO. Analyses of the product distributions suggest that for TMO propane activation the redox mechanism seems to prevail while the REO activate it by adsorbed oxygen. [ABSTRACT FROM AUTHOR]