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Crystalline Peaks (crystalline + peak)

Distribution by Scientific Domains

Polymers and Materials Science	50%

Selected Abstracts

Unusual Crystallization Behavior in Nylon-6 and Nylon-6/Montmorillonite Nanocomposite Films

MACROMOLECULAR RAPID COMMUNICATIONS, Issue 14 2004
Zhudi Zhao
Abstract Summary: The crystallization behavior of nylon-6 and nylon-6/montmorillonite nanocomposite films with different heat histories was investigated by wide-angle X-ray diffraction (WAXD). For nylon-6 films isothermally crystallized above 170,°C or annealed at 200,°C and then quenched in ice water, a crystalline peak appeared at 2,,=,28.5°. This crystalline peak was strong in intensity for the former and weak for the latter. However, for nylon-6 films cooled in air after isothermal crystallization or annealing, no crystalline peak at 2,,=,28.5° was observed in the WAXD patterns. For nylon-6/montmorillonite nanocomposite films annealed above 140,°C, a crystalline double peak was observed between the ,1 and ,2 peaks. The possible origins of the peak at 2,,=,28.5° and the crystalline double peak are discussed. WAXD patterns of isothermally crystallized nylon-6/montmorillonite nanocomposite films. [source]

Solubility studies on valdecoxib in the presence of carriers, cosolvents, and surfactants

DRUG DEVELOPMENT RESEARCH, Issue 1 2004
Kashappa Goud H. Desai
Abstract Enhancement of the solubility of valdecoxib was examined using a series of hydrophilic carriers (mannitol, polyethylene glycol (PEG) 4000, PEG 6000, PEG 8000, and urea), surfactants (Tween-20, Tween-80, and sodium lauryl sulfate [SLS]) and cosolvents (ethanol, methanol, and glycerol) at 37°C. The solubility of valdecoxib could be enhanced significantly using PEG 4000 as a carrier, ethanol as cosolvent, and SLS as a surfactant. Because the solubility of valdecoxib increased dramatically in the presence of polyethylene glycols, these are suitable dispersing agents for preparing solid dispersions containing valdecoxib. Gibbs free energy (,G) values were all negative for all hydrophilic carriers tested, indicating the spontaneous nature of valdecoxib solubilisation. Among the cosolvents, ethanol exhibited higher solubilization potential than methanol and glycerol. As the dielectric constant of the cosolvent,water mixtures decreased, the solubility of valdecoxib increased. Finally, SLS exerted maximum solubilization of valdecoxib when compared to Tween-20 or Tween-80. The crystallinity of valdecoxib was explored by X-ray diffraction study and showed numerous crystalline peaks. Examination of surface morphology by scanning electron microscopy depicted a near spherical shape of valdecoxib with irregular surface characteristics. Drug Dev. Res. 62:41,48, 2004. © 2004 Wiley-Liss, Inc. [source]

Thermal stability of porous it -PMMA thin film obtained by the extraction of st -PMAA from it -PMMA/st -PMAA stereocomplex with layer-by-layer assembly on a substrate

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 15 2010
Hiroharu Ajiro
Abstract The functionality of porous isotactic (it) poly(methyl methacrylate) (PMMA) thin films, which were previously developed by the selective extraction of syndiotactic (st) poly(methacrylic acid) (PMAA) from the it -PMMA/st -PMAA stereocomplex thin film on a substrate using the layer-by-layer assembly method was investigated after thermal treatment (70, 80, and 90 °C) in water for 4 h. Quartz crystal microbalance analysis and infrared spectra measurements revealed that the st -PMAA incorporation ability of the porous it -PMMA thin film decreased in order at 80 and 90 °C, while there was no decrease observed at 70 °C. X-ray diffraction analysis also supported the thermal stability of the porosity at 70 °C, whereas two it -PMMA crystalline peaks (2, = 9° and 14°) were generated during heating at 90 °C. The loss of the functionality of the it -PMMA thin film was thus shown to be due to crystallization, which was caused by the increase in polymer-chain mobility during the heating process. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3265,3270, 2010 [source]

Physical properties of edible films based on cassava starch as affected by the plasticizer concentration

PACKAGING TECHNOLOGY AND SCIENCE, Issue 2 2008
P. V. A. Bergo
Abstract The aim of this work was to investigate the effect of glycerol contents on physical properties of cassava starch films. The films were prepared from film-forming solutions (FFS) with 2g cassava starch/100g water and 0, 15, 30 and 45g glycerol/100g starch, and were analysed to determine its mechanical properties by tensile tests, the glass-transition temperature (Tg) by differential scanning calorimetry (DSC) and the crystallinity by X-ray diffraction (XRD). The infrared spectra of the films were also recorded. The resistance values of the films decreased, while those of the elasticity increased with an increase in glycerol concentration due to the plasticizer effect of glycerol, which was also observed in DSC curves. The Tg of the films prepared decreased with the glycerol content. However, for samples with 30 and 45g glycerol/100g starch, two Tg curves were observed, probably due to a phase separation phenomenon. According to the XRD diffractograms, the films with 0 and 15gglycerol/100g starch presented an amorphous character, but some tendency to show crystalline peaks were observed for films with 30 and 45g glycerol/100g starch. The results obtained with Fourier transform infrared (FTIR) corroborated these observations. Copyright © 2007 John Wiley & Sons, Ltd. [source]