Differential Scanning Calorimetry (differential + scanning_calorimetry)

Distribution by Scientific Domains
Distribution within Polymers and Materials Science

Kinds of Differential Scanning Calorimetry

  • dynamic differential scanning calorimetry

  • Terms modified by Differential Scanning Calorimetry

  • differential scanning calorimetry analysis
  • differential scanning calorimetry experiment
  • differential scanning calorimetry measurement
  • differential scanning calorimetry result
  • differential scanning calorimetry studies

  • Selected Abstracts


    STUDY OF SAGO STARCH (METROXYLON SAGU) GELATINIZATION BY DIFFERENTIAL SCANNING CALORIMETRY

    JOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 2 2001
    YAAKOB B. CHE MAN
    Differential scanning calorimetry (DSC), at various heating rates (1,30C/min) and water:starch ratios (0.1:1,4:1), was used to study gelatinization phenomena of sago starch. The results showed that the gelatinization temperature and enthalpy (, H) of starches in excess water were 60,77C and 15.5,15.8 J/g, respectively. , H of gelatinization remained substantially the same at excess water contents, but decreased significantly beyond a water:starch ratio of 1.3:1. A single endothermic transition (G) that transformed into a double endotherm (G and M1) and only M1 occurred, respectively, at excess, intermediate and limited water contents. At 50% water content, evidence of the M1 endotherm was observed, and 85C represented the effective conclusion temperature (Tm) at the end of melting for sago starch. The experimental data were treated thermody-namically by applying an equation describing phase transitions of semi-crystalline polymers. The calculated value for the melting point of the undiluted polymer (Tm) was 432 K (R2= 0.96). [source]


    Effect of long-term natural aging on the thermal, mechanical, and viscoelastic behavior of biomedical grade of ultra high molecular weight polyethylene

    JOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2010
    H. Fouad
    Abstract In the total joint prostheses, Ultra High Molecular Weight Polyethylene (UHMWPE) may undergo an oxidative degradation in the long term. The overall properties of UHMWPE are expected to be altered due to the oxidative degradation. The goal of this study is to investigate the effects of natural aging up to 6 years in air on the thermal, mechanical, and viscoelastic properties of UHMWPE that was used in total joint replacement. The changes in UHMWPE properties due to aging are determined using Differential Scanning Calorimetry (DSC), uniaxial tensile tests, and Dynamic Mechanical Analysis (DMA). The DSC results show that the lamellar thickness and degree of crystallinity of UHMWPE specimens increase by 38% and 12% due to aging. A small shoulder region in the DSC thermograms is remarked for aged specimens, which is an indication of formation of new crystalline forms within their amorphous region. The tensile properties of aged and nonaged UHMWPE specimens show a significant decrease in the elastic modulus, yield, fracture stresses, and strain at break due to aging. The DM testing results indicate that the storage modulus and creep resistance of UHMWPE specimens decrease significantly due to aging. Also, it is remarked that the , relaxation peak for aged UHMWPE specimens occurs at lower temperature compared to nonaged ones. The significant reduction in the strength and creep resistance of UHMWPE specimens due to aging would affect the long-term clinical performance of the total joint replacement and should be taken into consideration during artificial joint design. 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]


    Thermal Properties, Heat Sealability and Seal Attributes of Whey Protein Isolate/ Lipid Emulsion Edible Films

    JOURNAL OF FOOD SCIENCE, Issue 7 2001
    S-J. Kim
    ABSTRACT: From 5% w/v whey protein isolate (WPI), whey protein/lipid emulsion edible films were produced that were sorbitol- or glycerol-plasticized, containing butterfat (0.2% w/v) or candelilla wax (0.8% w/v). Thermal properties of the films determined by Differential Scanning Calorimetry (DSC) showed onset temperatures (To) of 126 to 127 C for sorbitol- and 108 to 122 C for glycerol-plasticized films. To values were used as the basis for heat sealing temperatures. Temperature (110, 120, 130 C), pressure (296,445 kPa), and dwell time (1,3 s) affected seal strength. Optimum heat sealing temperature was 130 C for sorbitol- and 110 C for glycerol-plasticized films. All films were heat sealable with an impulse heat-sealer. Electron Spectroscopy for Chemical Analysis (ESCA) of the surfaces of both sealed and unsealed films showed increase in hydrogen and covalent bonds involving C-O-H and N-C, which may be the main forces responsible for the sealed joint formation of the films. [source]


    Crystallization Kinetics of Amorphous Lactose as a Function of Moisture Content Using Isothermal Differential Scanning Calorimetry

    JOURNAL OF FOOD SCIENCE, Issue 2 2000
    C. J. Kedward
    ABSTRACT: Isothermal differential scanning calorimetry (DSC) was used to study the crystallization kinetics of amorphous lactose at 3 moisture contents. Each sample was heated to several temperatures between Tg and Tm. After subtraction of an induction time, the Avrami equation was used to model the data and a Lauritzen-Hoffman like expression used to fit the crystallization rates between Tg and Tm. The highest Tm/Tg ratio and crystallization rate were observed for the sample containing the most moisture. Conversely the lowest Tm/Tg ratio and crystallization rate were observed for the sample containing the least moisture. Evidence for multiple transitions was seen. The Avrami equation may not be the best way to model such data. [source]


    Evaluation of the Self-Heating Tendency of Vegetable Oils by Differential Scanning Calorimetry

    JOURNAL OF FORENSIC SCIENCES, Issue 6 2008
    Amlie Baylon M.S.
    Abstract:, The evaluation of the self-heating propensity of a vegetable (or animal) oil may be of significant importance during the investigation of a fire. Unfortunately, iodine value and gas chromatographic-mass spectrometric analysis do not lead to meaningful results in this regard. To the contrary, differential scanning calorimetry (DSC), which does not measure the chemical composition of the oil, but rather its thermodynamic behavior, produces valuable results. After a thorough literature review on the autooxidation of vegetable oils, several oils with different self-heating tendencies were analyzed using a Mettler-Toledo differential scanning calorimeter DSC 25 between 40C and 500C. Analyses were carried out both under air and nitrogen atmosphere to identify the phenomena due to autooxidation reactions. Using DSC, it was possible to observe the induction period of the oil (when available), the three different exothermic events, and the autoignition temperature (relatively independent of the oil type). [source]


    Estimation of the fragility index of indomethacin by DSC using the heating and cooling rate dependency of the glass transition

    JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 6 2004
    Joaquim J. Moura Ramos
    Abstract In this study we have investigated the features of the glass transition relaxation of indomethacin using Differential Scanning Calorimetry (DSC). The purpose of this work is to provide an estimation of the activation energy at the glass transition temperature, as well as of the fragility index, of amorphous indomethacin from DSC data. To do so, the glass transition temperature region of amorphous indomethacin was characterized in both cooling and heating regimes. The activation energy for structural relaxation (directly related to glass fragility) was estimated from the heating and cooling rate dependence of the location of the DSC profile of the glass transition. The obtained results were similar in the heating and in the cooling modes. The results on the fragility index of indomethacin obtained in the present study, m,=,60 in the cooling mode and m,=,56 in the heating mode, are compared with other values previously published in the literature. 2004 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 93:1503,1507, 2004 [source]


    Using Differential Scanning Calorimetry to Follow How Gelcasting Proceeds

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2007
    BoonSing Ng
    Differential scanning calorimetry studies on aqueous low-toxicity monomer,crosslinker gelcasting systems loaded with zirconia powder provided information on the onset and kinetics of the polymerization reaction. A simple procedure was developed to determine the relative importance of the individual components on the gelation process. It was found that the thermal stability and dissociation of the initiator control the gelation rate and that the zirconia particles accelerate the gelation. [source]


    Illumination of Cellulose with Linearly Polarized Visible Light

    MACROMOLECULAR SYMPOSIA, Issue 1 2008
    A. Konieczna - Molenda
    Abstract Summary: Aqueous suspensions of cellulose of long polysaccharide chains, were illuminated with visible polarized light (VPL) for 20 and 50 hrs. Crystal structure, thermal properties with Differential Scanning Calorimetry (DSC) and degree of polymerization (DP) of the samples were determined. Additionally, kinetic of enzymatic as well as acid-catalyzed hydrolysis of cellulose was estimated. Illumination of cellulose with VPL for 50 hrs increased its DP by 15%. X-ray diffraction patterns revealed that the illumination resulted in an increase in the amount of cellulose crystalline phase. The DSC measurements indicated differences in the water molecules distribution depending on the sample treatment confirming an increase in the crystallinity of the illuminated cellulose. After prolonged illumination, cellulose was resistant to oxidation and had lower susceptibility to enzymatic and acid-catalyzed hydrolysis. [source]


    Effect of EPDM on Morphology, Mechanical Properties, Crystallization Behavior and Viscoelastic Properties of iPP+HDPE Blends

    MACROMOLECULAR SYMPOSIA, Issue 1 2007
    Nina Vranjes
    Abstract Summary: Blends of isotactic polypropylene (iPP) and high density polyethylene (HDPE) with and without ethylene-propylene-diene (EPDM) terpolymer as compatibilizer were systematically investigated to determine the influence of the EPDM on blends properties. The morphology was studied by Scanning Electron Microscopy (SEM). Mechanical properties of investigated systems: tensile strength at break, elongation at break, yield stress and Izod impact strength were determined. Crystallization behavior was determined by Differential Scanning Calorimetry (DSC). Dynamic Mechanical Analysis (DMA) was used to determined the storage modulus (E,), loss modulus (E,), and loss tangent (tan ,). The PP+HDPE blend revealed poor adhesion between PP and HDPE phases. Finer morphology was obtained by EPDM addition in PP+HDPE blends and better interfacial adhesion. Addition of HDPE to PP decreased tensile strength at break, elongation and yield stress. Decrease of tensile strength and yield stress is faster with EPDM addition in PP+HDPE blends. Elongation at break and impact strength was significantly increased with EPDM addition. The addition of EPDM in PP+HDPE blends did not significantly change melting points of PP phase, while melting points of HDPE phase was slightly decreased in PP+HDPE+EPDM blends. The EPDM addition increased the percentage of crystallization (Xc) of PP in PP+HDPE blends. The increase of Xc of HDPE was found in the blend with HDPE as matrix. Dynamical mechanical analysis showed glass transitions of PP and HDPE phase, as well as the relaxation transitions of their crystalline phase. By addition of EPDM glass transitions (Tg) of HDPE and PP phases in PP+HDPE blends decreased. Storage modulus (E,) vs. temperatures (T) curves are in the region between E,/T curves of neat PP and HDPE. The decrease of E, values at 25,C with EPDM addition in PP+HDPE blends is more pronounced. [source]


    Preparation and properties of polyurethane/montmorillonite nanocomposites cured under room temperature

    POLYMER COMPOSITES, Issue 5 2006
    Hangbin Jiang
    The polyurethane/C16C18 -MMT (the montmorillonite modified with cetyloctadecyldimethyl ammonium bromide) nanocomposites were synthesized by intercalative polymerization and cured under room temperature. The d -spacing and the dispersion of the C16C18 -MMT in the nanocomposites were measured by X-ray Diffraction (XRD) and Transmission Electron Microscope (TEM). The mechanical and thermal properties of the nanocomposites were measured by Universal Testing System, Electric Anti-fold Instrument, Thermogravimetric Analysis (TGA), and Differential Scanning Calorimetry (DSC). It was found out that introducing C16C18 -montmorillonite (MMT) in the polyurethane (PU) displayed good mechanical properties and thermal stability. Rheology behavior in liquid state showed that the addition of the C16C18 -MMT to PU resulted in low gel time and high viscosity. POLYM. COMPOS. 27:470,474, 2006. 2006 Society of Plastics Engineers. [source]


    Synthesis and characterization of styrene butadiene rubber,Bentonite clay nanocomposites

    POLYMER ENGINEERING & SCIENCE, Issue 7 2009
    Sugata Chakraborty
    In the present study, naturally occurring unfractionated bentonite clay was used to prepare styrene butadiene rubber/bentonite clay nanocomposite by latex stage blending. The bentonite clay was organo-modified by in situ resol formation by the reaction of resorcinol and formaldehyde. The latex clay mixture was co-coagulated with acid. The resulting clay masterbatch was compounded and evaluated by Fourier Transform Infrared spectroscopy, X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), Energy Dispersive X-ray spectroscopy (EDS), Scanning Electron Microscopy, Thermogravimetric analysis, and Differential Scanning Calorimetry. XRD showed that the interplanar distance of the in situ resol-modified bentonite clay increased from 1.23 to 1.41 nm for the unmodified bentonite. TEM analysis indicated partial exfoliation and/or intercalation. EDS (Si and Al mapping) of the clay revealed the nature of the dispersion in the nanocomposites vis--vis the conventional styrene-butadiene rubber (SBR)/bentonite clay composite. Thermogravimetric analysis was used to compare the decomposition trends of the SBR/clay nanocomposites with the SBR/clay composite. The glass transition temperature of SBR/clay nanocomposites increased as compared with that of neat SBR. Substantial improvement in most of the other mechanical properties was also observed in case of the nanocomposites. POLYM. ENG. SCI., 2009. 2009 Society of Plastics Engineers [source]


    Relaxation map of PETg-montmorillonite composites: Nanofiller concentration influence on , and , relaxation processes,

    POLYMER ENGINEERING & SCIENCE, Issue 5 2009
    H. Couderc
    Samples of polyethylene-1.4-cyclohexylenedimethylene terephthalate glycol (PETg) with different filler contents were prepared by a master batch process. The intercalated dispersion state of montmorillonite (MMT) was characterized using X-Ray Diffraction. Two different sample series are put in evidence with different basal distances (3.31 and 3.48 nm). The influence of nanofiller on , and , relaxations was studied by Dielectric Relaxation Spectroscopy and Differential Scanning Calorimetry. The use of these two techniques allowed us to determine accurately the fragility index m at the glass transition temperature Tg. For Tg, m, the Kauzmann temperature TK, and the relaxation time at Tg ,(Tg), we showed a decrease of the values more important for 3.48 nm basal distance than for 3.31 nm. The , did not seem affected in its apparent activation energy Ea by the MMT addition. POLYM. ENG. SCI., 2009. 2008 Society of Plastics Engineers [source]


    Evaluation of three methods for the measurement of crystallinity of pet resins, preforms, and bottles

    POLYMER ENGINEERING & SCIENCE, Issue 11 2000
    Z. Bashir
    The control of crystallization is important at all processing stages of the PET bottle industry, from the manufacture of bottle resins to the fabrication of preforms and bottles. In this work, we sought to evaluate critically three methods of crystallinity measurement. We have used density, Differential Scanning Calorimetry (DSC), and Modulated Differential Scanning Calorimetry (MDSC) to study the crystallinity of PET chips, preforms, and bottles. The accuracy, precision, and general validity of each technique and the problems of interpretation are discussed. [source]


    Phase Transitions in [Ca(H2O)4](NO3)2 Studied by Differential Scanning Calorimetry, X-Ray Single Crystal Diffraction and Neutron Powder Diffraction.

    CHEMINFORM, Issue 25 2007
    Part 1.
    Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source]


    System Ln,Fe,O (Ln: Ho, Er): Thermodynamic Properties of Ternary Oxides Using Differential Scanning Calorimetry and Solid-State Electrochemical Cells.

    CHEMINFORM, Issue 37 2006
    S. C. Parida
    Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source]


    Thermal, phase transition and spectral studies in erythromycin pseudopolymorphs: dihydrate and acetone solvate

    CRYSTAL RESEARCH AND TECHNOLOGY, Issue 12 2006
    Zhanzhong Wang
    Abstract The thermal, phase transition and spectral studies of erythromycin A dihydrate and acetone solvate were performed by Differential Scanning calorimetry (DSC), Thermo Gravimetry (TG-DTA), X-Ray Powder Diffraction (XRPD) and Fourier Transform Infra-Red (FTIR) spectrum. The non-thermal kinetic analysis of erythromycin A dihydrate was carried out by DSC at different heating rates in dynamic nitrogen atmosphere. The result showed that heating rate has substantial influence on the thermal behavior of erythromycin dihydrate. The Arrhenius parameters were estimated according to the Kissinger method. Corresponding to dehydration of dihydrate, melting of dehydrated dihydrate, phase transition from dehydrated dihydrate to anhydrate, and melting of anhydrate, the calculated activation energy were 39.60, 269.85, 261.23, and 582.16 kJmol,1, the pre-exponential factors were 3.46 103, 8.06 1032, 9.23 1030, and 7.29 1063 s,1, respectively. Ozawa method was used to compare activation energy values calculated by Kissinger method. ( 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Crystal structures and isotope effect on Na5H3(SeO4)42H2O and Na5D3(SeO4)42D2O crystals

    CRYSTAL RESEARCH AND TECHNOLOGY, Issue 8 2010
    T. Fukami
    Abstract Differential scanning calorimetry (DSC) and X-ray diffraction measurements have been performed on pentasodium trihydrogen tetraselenate dihydrate Na5H3(SeO4)42H2O and deuterated Na5D3(SeO4)42D2O crystals. Any distinct anomaly around 428 K in the DSC curves for both crystals is suggested to be caused by a chemical reaction of thermal decomposition with hydrolysis at high temperature. The space group symmetry (triclinic P) and the structure parameters are determined at room temperature. The hydrogen atom in the centrosymmetric O-H(D)-O hydrogen bond of both crystals is found to be equally distributed at two equivalent sites in the bond. The expansions of two O-H-O hydrogen bonds by the substitution of deuterium are observed to be 0.016(6) and 0.011(4) . The geometric isotope effect on hydrogen bonds is confirmed to be existed in Na5H3(SeO4)42H2O. ( 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Synthesis and characterization of potassium magnesium sulphate hexahydrate crystals

    CRYSTAL RESEARCH AND TECHNOLOGY, Issue 4 2006
    M. Dhandapani
    Abstract Potassium magnesium sulphate hexahydrate (picromerite) was synthesized and single crystals were obtained from saturated aqueous solution by slow evaporation method at room temperature. The crystals were bright, colourless and transparent having well defined external faces. The grown crystals were characterized through Fourier Transform Infrared (FTIR) spectral studies and thermal analysis. The FTIR data were used to assign the characteristic vibrational frequencies of the various chemical bonds in the compound. The compound crystallizes in monoclinic lattice with the space group P21/c. The thermogravimetry (TG) indicates the removal of only two water molecules around 100 C. A suitable decomposition pattern was formulated based on the percentage weight losses observed in TG of the compound. The results of differential thermal analysis (DTA) conform to the results of TGA. Differential scanning calorimetry (DSC) analysis carried out at high temperature suggests that the occurrence of two phase transitions in the crystal between 140 and 180 C. When the crystal was cooled below the room temperature up to ,170 C, no thermal anomaly was observed. ( 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Inhomogeneity of composition in near-stoichiometric LiNbO3 single crystal grown from Li rich melt

    CRYSTAL RESEARCH AND TECHNOLOGY, Issue 4 2006
    L. Gao
    Abstract A near-stoichiometric LiNbO3 single crystal has been grown by the Czochralski technique from a melt of 58.5 mol% Li2O. Its composition homogeneity was assessed by measuring the UV absorption edge. It was found that the maximum composition difference is about 0.03 mol% in the radial direction and 0.05 mol% in the axial direction. Differential scanning calorimetry (DSC) analysis was performed on the powder from the synthesized raw material and the frozen melt after crystal growth. The analytical results indicate that, during crystal growth, the magnitude of lithium volatilization from the melt surface is more than the degree of segregation from the crystal. The volatilized lithium diffuses into the crystal to compensate for the lithium segregation in the LiNbO3 crystal. ( 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    The Dry Limit of Microbial Life in the Atacama Desert Revealed by Calorimetric Approaches

    ENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 5 2008
    N. Barros
    Abstract The Atacama desert in Chile is one of the driest and most lifeless environments on Earth. It rains possibly once a decade. NASA examined these soils as a model for the Martian environment by comparing their degradation activity with Martian soil and looking for "the dry limit of life". The existence of heterotrophic bacteria in Atacama soil was demonstrated by DNA extraction and by the isolation of microorganisms. So far, however, no data have been available about the metabolic activities in these soils due to the limitations of the existing methodologies when applied to desert soils. Calorimetry was used to obtain information on the metabolic and thermal properties of eleven soil samples collected at different sites in the Atacama desert. Differential scanning calorimetry and isothermal calorimetry were employed to determine the pyrolysis properties of the carbon-containing matter and to measure biomass and microbial metabolism. They were compared to other soil properties such as total carbon and nitrogen, carbon to nitrogen ratio and pH. There was measurable organic matter in nine of the eleven samples and the heat of pyrolysis of those soils was correlated to the carbon content. In five of the eleven samples no biomass could be detected and the existence of basal microbial metabolism could not be established because all samples showed endothermic activity, probably from inorganic reactions with water. Six samples showed microbial activation after the addition of glucose. Carbon content, nitrogen content and the microbial activity after glucose amendment were correlated to the altitude and to the average minimum temperature of the sampling sites calculated from meteorological data. The detectable microbial metabolism was more dissipative with increasing altitude and decreasing temperature. [source]


    Consecutive Nucleation Events During Divetrification of Zr52.5Cu17.9Ni14.6Al10Ti5 Bulk Metallic Glass,

    ADVANCED ENGINEERING MATERIALS, Issue 11 2008
    L. Yang
    Differential scanning calorimetry revealed two exothermal peaks in Zr52.5Cu17.9Ni14.6 -Al10Ti5 bulk metallic glass during divetrification. Analysis of the calorimetry data as well as in-situ X-ray diffraction experiments show that the exothermal peaks correspond to two nucleation events, controlled by interface and long-range diffusion, respectively. [source]


    Specific cleavage of the DNase-I binding loop dramatically decreases the thermal stability of actin

    FEBS JOURNAL, Issue 18 2010
    Anastasia V. Pivovarova
    Differential scanning calorimetry was used to investigate the thermal unfolding of actin specifically cleaved within the DNaseI-binding loop between residues Met47-Gly48 or Gly42-Val43 by two bacterial proteases, subtilisin or ECP32/grimelysin (ECP), respectively. The results obtained show that both cleavages strongly decreased the thermal stability of monomeric actin with either ATP or ADP as a bound nucleotide. An even more pronounced difference in the thermal stability between the cleaved and intact actin was observed when both actins were polymerized into filaments. Similar to intact F-actin, both cleaved F-actins were significantly stabilized by phalloidin and aluminum fluoride; however, in all cases, the thermal stability of the cleaved F-actins was much lower than that of intact F-actin, and the stability of ECP-cleaved F-actin was lower than that of subtilisin-cleaved F-actin. These results confirm that the DNaseI-binding loop is involved in the stabilization of the actin structure, both in monomers and in the filament subunits, and suggest that the thermal stability of actin depends, at least partially, on the conformation of the nucleotide-binding cleft. Moreover, an additional destabilization of the unstable cleaved actin upon ATP/ADP replacement provides experimental evidence for the highly dynamic actin structure that cannot be simply open or closed, but rather should be considered as being able to adopt multiple conformations. Structured digital abstract ,,MINT-7980274: Actin (uniprotkb:P68135) and Actin (uniprotkb:P68135) bind (MI:0407) by biophysical (MI:0013) [source]


    Bismuth,Ceramic Nanocomposites with Unusual Thermal Stability via High-Energy Ball Milling,

    ADVANCED FUNCTIONAL MATERIALS, Issue 10 2003
    M.A. Meitl
    Abstract Electrically conducting nanocomposites of bismuth metal and insulating ceramic phases of SiO2 and MgO were generated via high-energy ball milling for 24 h using zirconia milling media. The resulting nanocomposites contain Bi nanoparticles with sizes down to 5 nm in diameter. The morphology is a strong function of the oxide phase: specifically, the Bi appears to wet MgO while it forms spherical nanoparticles on the SiO2. X-ray diffraction measurements indicate a nominal bismuth grain size of 50 nm, and peak fitting to a simple bidisperse model yields a mixture of approximately 57,% bulk bismuth and 43,% 27 nm diameter crystallites. Nanoparticles as small as 5 nm are observed in transmission electron microscopy (TEM), but may not constitute a significant volume fraction of the sample. Differential scanning calorimetry reveals dramatic broadening in the temperatures over which melting and freezing occur and a surprising persistence of nanostructure after thermal cycling above the melting point of the Bi phase. [source]


    Synthesis of Novel Chiral Ionic Liquids and Their Phase Behavior in Mixtures with Smectic and Nematic Liquid Crystals

    HELVETICA CHIMICA ACTA, Issue 11 2004
    Martin Tosoni
    Alkylation of 1-alkyl-1H -imidazoles 2a,f with citronellyl bromide 1b opens access to chiral 1H -imidazolium bromides 3a,f (Scheme,1). A similar strategy yielded the chiral pyridinium ionic liquid 6 (Scheme,2). Dialkylation of 1H -imidazole (7) gave the C2 -symmetric 1,3-dicitronellyl-1H -imidazolium bromide (8) (Scheme,3). Differential scanning calorimetry and optical polarizing microscopy revealed smectic mesophases for 1-citronellyl-3-tetradecy-1H -limidazolium bromide (3e) and 1-citronellylpyridinium bromide (6) (Table). In binary mixtures with smectic and nematic liquid crystals 9 and 10, 1-citronellyl-3-methyl-1H -imidazolium bromide (3a) behaved differently. Increasing quantities of 3a cause a decrease of the smectic-phase width for the mixture 3a/9 (Fig.,3), whereas the phase width of the nematic phase for 3a/10 remained nearly constant (Fig.,4). [source]


    Functional and structural properties and in vitro digestibility of acylated hemp (Cannabis sativa L.) protein isolates

    INTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 12 2009
    Shou-Wei Yin
    Summary The effects of succinylation and acetylation on some functional, structural properties and in vitro trypsin digestibility of hemp protein isolate (HPI) were investigated. The extent of acylation gradually increased from 0 to 60,70%, with the anhydride-to-protein ratio increasing from 0 to 1.0 g g,1. Size exclusion chromatography showed that succinylation led to formation of more soluble protein aggregate than acetylation, especially at anhydride levels higher than 0.1 g g,1. Succinylation led to gradual increase in protein solubility (PS) from 30 to 85,90%, while in the acetylation case, the PS was improved only at low anhydride levels, increasing from 30 to about 50% with anhydride-to-protein ratio increasing from 0 to 0.2 g g,1. At neutral pH, the emulsifying activity indexes (EAI) of HPI was 22.1 m2 g,1, and the EAI linearly and significantly increased with the extent of acylation. The EAIs of succinylated and acetylated HPI (1.0 g g,1) were 119.0 and 54.4 m2 g,1, respectively. Differential scanning calorimetry (DSC) and intrinsic fluorescence spectrum analyses indicated gradual structural unfolding of proteins, or exposure of hydrophobic clusters to the solvent, especially at higher anhydride levels. Additionally, the in vitro trypsin digestibility was significantly improved by the succinylation. The results indicated that the chemical acylation treatment (especially succinylation) could be applied to modify some selected functional properties of hemp proteins, especially PS and emulsifying ability. [source]


    Hexagonal and cubic TiOF2

    JOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 4 2010
    Samuel Shian
    The chemical, electrochemical, optical and electro-optical properties of titanium oxyfluoride, TiOF2, have led to interest in this compound for a number of applications. Prior analyses have indicated that TiOF2 possesses a simple cubic structure (space group Pmm) at room temperature. Three-dimensional nanostructured assemblies of polycrystalline TiOF2 have recently been synthesized via chemical conversion of intricate SiO2 structures by metathetic reaction with TiF4(g). Rietveld analysis has been used to evaluate the structure of the TiOF2 product formed by such reaction at 623,K. Unlike prior reports, this TiOF2 product possessed a hexagonal structure (space group Rc) at room temperature. Upon heating through 333,338 K, the hexagonal TiOF2 polymorph converted into cubic (Pmm) TiOF2. Differential scanning calorimetry and X-ray diffraction analyses have been used to evaluate this thermally induced phase transformation. [source]


    Investigation of the gelatinization and extrusion processes of corn starch

    ADVANCES IN POLYMER TECHNOLOGY, Issue 1 2002
    Roberta C. R. Souza
    Abstract The gelatinization and extrusion processes of corn starch were studied. Differential scanning calorimetry was used to determine the gelatinization temperature as a function of the water content. Plasticized corn starch was processed in single- and twin-screw extruders to produce thermoplastic materials. The mechanical properties of the films obtained in the twin-screw extruder with the addition of different quantities of water were evaluated. Dynamic mechanical analysis applied to thermoplastic starch samples obtained with 33% (w/w) total plasticizers showed two transitions, attributed to the presence of two phases in the starch,glycerol,water system. 2002 John Wiley & Sons, Inc. Adv Polym Techn 21: 17,24, 2002; DOI 10.1002/adv.10007 [source]


    Gellan,adipic acid blends crosslinked by means of a dehydrothermal treatment

    JOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010
    Niccoletta Barbani
    Abstract Blends of gellan gum (GE) and adipic acid (ADA), at various ratios, were manufactured in the form of films by casting from aqueous solutions and crosslinked by a dehydrothermal treatment (DHT). The materials, before and after DHT, were characterized by both physicochemical tests and cellular adhesion and growth on the film surfaces. The total reflection and spotlight Fourier transform infrared (FTIR) spectroscopy and optical and scanning electron microscopy showed the presence of both GE-rich and ADA-rich regions and the formation of ester groups after DHT. Differential scanning calorimetry, thermogravimetric analysis, and dynamic mechanical analysis (DMA) showed that the crosslinking by DHT made the materials more thermally stable. The swelling in water, which diminished in the films subjected to DHT, confirmed that the crosslinking enhanced the whole stability of the material. DMA also showed that the behavior of the GE,ADA blends was quite similar to that of some living tissues, such as the skin. The cell cultures indicated that the materials, especially that with a 6 : 10 ADA-to-GE ratio, were very able to promote cellular adhesion and proliferation. In conclusion, the GE,ADA crosslinked blends appeared very suitable for a use as biomaterials; in particular, the cell cultures indicated that they might be useful as scaffolds for tissue reconstruction. 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]


    Synthesis and properties of poly(butylene terephthalate)/multiwalled carbon nanotube nanocomposites prepared by in situ polymerization and in situ compatibilization

    JOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2010
    Fangjuan Wu
    Abstract A novel cyclic initiator was synthesized from dibutyl tin(IV) oxide and hydroxyl-functionalized multiwalled carbon nanotubes (MWNTs) and was used to initiate the ring-opening polymerization of cyclic butylene terephthalate oligomers to prepare poly(butylene terephthalate) (PBT)/MWNT nanocomposites. The results of Fourier transform infrared and NMR spectroscopy confirmed that a graft structure of PBT on the MWNTs was formed during the in situ polymerization; this structure acted as an in situ compatibilizer in the nanocomposites. The PBT covalently attached to the MWNT surface enhanced the interface adhesion between the MWNTs and PBT matrix and, thus, improved the compatibility. The morphologies of the nanocomposites were observed by field emission scanning electron microscopy and transmission electron microscopy, which showed that the nanotubes were homogeneously dispersed in the PBT matrix when the MWNT content was lower than 0.75 wt %. Differential scanning calorimetry and thermogravimetric analysis were used to investigate the thermal properties of the nanocomposites. The results indicate that the MWNTs acted as nucleation sites in the matrix, and the efficiency of nucleation was closely related to the dispersion of the MWNTs in the matrix. Additionally, the thermal stability of PBT was improved by the addition of the MWNTs. 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]


    A novel microencapsulation of neem (Azadirachta Indica A. Juss.) seed oil (NSO) in polyelectrolyte complex of ,-carrageenan and chitosan

    JOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2009
    Nirmala Devi
    Abstract Microcapsules containing neem (Azadirachta Indica A. Juss.) seed oil (NSO) were prepared by encapsulation of natural liquid pesticide NSO in a polyelectrolyte complex of ,-carrageenan and chitosan. The optimum ratio between carrageenan and chitosan to form a stable polyelectrolyte complex was found as 1 : 0.36. The microencapsulation method for NSO loading was also optimized. SEM study demonstrated that the surface of the microcapsules became more irregular as oil loading increased. The release rates of NSO were studied by varying the percentage of oil loading, concentration of cross-linking agent, and polymer concentration. Fourier transform infrared spectroscopy (FTIR) study confirmed the complex formation between ,-carrageenan and chitosan. Differential scanning calorimetry (DSC) and FTIR study indicated the absence of any significant interaction between polyelectrolyte complex of ,-carrageenan -chitosan and NSO. 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source]