Showing papers on "Differential scanning calorimetry published in 2011"
TL;DR: Control of silk structure via TCWVA represents a significant improvement in the fabrication of silk-based biomaterials, where control of structure-property relationships is key to regulating material properties.
547 citations
01 Jan 2011
TL;DR: Amorphous cellulose was obtained from different types of celluloses (microcrystalline cellulose, dissolving pulp and cotton cellulose), by regeneration with ethanol from their solutions in an SO2-diethylaminedimethylsulfoxide (SO2-DEA-DMSO) solvent system as discussed by the authors.
Abstract: Amorphous cellulose was obtained from different types of celluloses (microcrystalline cellulose, dissolving pulp and cotton cellulose), by regeneration with ethanol from their solutions in an SO2-diethylaminedimethylsulfoxide (SO2-DEA-DMSO) solvent system. Different techniques, X-ray diffraction (XRD), FTIR spectroscopy and differential scanning calorimetry (DSC) were used to estimate the crystallinity degree. The values obtained for amorphous celluloses were compared with those of the initial samples and correlated with their supramolecular structures. Viscosity measurements have shown that little or no depolymerization occurs during dissolution.
490 citations
TL;DR: Various new polynitro-1,2,4-triazoles containing a trinitromethyl group were synthesized by straightforward routes and exhibit high density, good thermal stability, acceptable oxygen balance, positive heat of formation, and excellent detonation properties, which, in some cases, are superior to those of TNT, RDX, and HMX.
Abstract: Various new polynitro-1,2,4-triazoles containing a trinitromethyl group were synthesized by straightforward routes. These high nitrogen and oxygen-rich compounds were fully characterized using IR and multinuclear NMR spectroscopy, elemental analysis, natural bonding orbital (NBO) analysis, and differential scanning calorimetry (DSC) and, in the case of 12, with single crystal X-ray structuring. The heats of formation for all compounds were calculated with Gaussian 03 (revision D.01) and then combined with experimentally determined densities to determine detonation pressures (P) and velocities (D) of the energetic materials (Cheetah 5.0). They exhibit high density, good thermal stability, acceptable oxygen balance, positive heat of formation, and excellent detonation properties, which, in some cases, are superior to those of TNT, RDX, and HMX.
320 citations
TL;DR: A coamorphous drug/drug combination between the two nonsteroidal anti-inflammatory drugs, naproxen and γ-indomethacin, was prepared and investigated and it was suggested that the two drugs formed a heterodimer.
Abstract: One of the challenges in drug development today is that many new drug candidates are poorly water-soluble, and one of the approaches to overcome this problem is to transfer a crystalline drug into its amorphous form, thus increasing dissolution rate and apparent solubility of the compound. In this study, a coamorphous drug/drug combination between the two nonsteroidal anti-inflammatory drugs, naproxen and γ-indomethacin, was prepared and investigated. At molar ratios of 2:1, 1:1 and 1:2, the drugs were quench cooled in order to obtain a coamorphous binary phase. Physical stability was examined at 277.15 and 298.15 K under dry conditions (phosphorus pentoxide) and analyzed with X-ray powder diffraction (XRPD). Intrinsic dissolution testing was carried out to identify dissolution advantages of the coamorphous form over its crystalline counterparts or amorphous indomethacin. Fourier transform infrared spectroscopy (FTIR) was used for analyses at the molecular level to detect potential molecular interactions. Differential scanning calorimetry (DSC) thermograms were employed to assess the glass transition temperatures (T(g)), and the results were compared with predicted T(g)s from the Gordon-Taylor equation. Results showed that naproxen could be made amorphous in combination with indomethacin while this was not possible with naproxen alone. Peak shifts in the FTIR spectra indicated molecular interactions between both drugs, and it is suggested that the two drugs formed a heterodimer. Therefore, samples at the 1:2 and 2:1 ratios showed recrystallization of the excess drug upon storage whereas the 1:1 ratio samples remained amorphous. Intrinsic dissolution testing showed increased dissolution rate of both drugs in the coamorphous form as well as a synchronized release for the 1:1 coamorphous blend. All T(g)s displayed negative deviations from the Gordon-Taylor equation with the 1:1 ratio showing the largest deviation. In a novel approach of predicting the glass transition temperature, the 1:1 drug ratio was inserted as an individual component in the Gordon-Taylor equation with the excess drug representing the second compound. This approach resulted in a good fit to the experimentally determined T(g)s.
294 citations
TL;DR: In this article, the authors deal with preparation, characterization, thermal properties and thermal reliability of n- eicosane microcapsules as novel phase change material (PCM) for thermal energy storage.
285 citations
TL;DR: This review focuses on the use of DSC for biochemical and pharmaceutical applications.
Abstract: Differential Scanning Calorimetry (DSC) is a highly sensitive technique to study the thermotropic properties of many different biological macromolecules and extracts. Since its early development, DSC has been applied to the pharmaceutical field with excipient studies and DNA drugs. In recent times, more attention has been applied to lipid-based drug delivery systems and drug interactions with biomimetic membranes. Highly reproducible phase transitions have been used to determine values, such as, the type of binding interaction, purity, stability, and release from a drug delivery mechanism. This review focuses on the use of DSC for biochemical and pharmaceutical applications.
285 citations
TL;DR: A seasonal chemical heat store based on the hydration/dehydration cycle of a magnesium sulphate (MgSO4) composite material has been developed in this article, where the active material needs to be dispersed to optimize the gas-solid reaction kinetics and the thermal power released/absorbed.
233 citations
TL;DR: In this paper, a differential scanning calorimeter instrument was used to measure the specific heat of the neat molten salt eutectic and after addition of nanoparticles, which was enhanced by 19-24%.
Abstract: Silica nanoparticles (1% by weight) were dispersed in a eutectic of lithium carbonate and potassium carbonate (62:38 ratio) to obtain high temperature nanofluids. A differential scanning calorimeter instrument was used to measure the specific heat of the neat molten salt eutectic and after addition of nanoparticles. The specific heat of the nanofluid was enhanced by 19–24%. The measurement uncertainty for the specific heat values in the experiments is estimated to be in the range of 1–5%. These experimental data contradict earlier experimental results reported in the literature. (Notably, the stability of the nanofluid samples was not verified in these studies.) In the present study, the dispersion and stability of the nanoparticles were confirmed by using scanning electron microscopy (SEM). Percolation networks were observed in the SEM image of the nanofluid. Furthermore, no agglomeration of the nanoparticles was observed, as confirmed by transmission electron microscopy. The observed enhancements are suggested to be due to the high specific surface energies that are associated with the high surface area of the nanoparticles per unit volume (or per unit mass).
228 citations
TL;DR: The purpose of this work was to study the mechanistic pathways of degradation of polysorbates (PS) 20 and PS80 in parenteral formulations, and found that PSs degrade mainly via autoxidation and also via hydrolysis at higher temperatures.
221 citations
TL;DR: In this paper, the effects of the type of plasticizer on the thermal properties and heat sealability of sago starch films were investigated, and the results showed that the 3:1 combination of sorbitol/glycerol was the best combination of plasticizers.
194 citations
TL;DR: In this article, the effect of different curing temperatures on the geopolymerization process, physical, mechanical and optical properties of a metakaolin-based geopolymers activated by alkali was studied systematically by means of differential scanning calorimetry (DSC), SEM, UV/Vis Spectrophotometry, Leaching analysis and Brunauer-Emmet-Teller method (BET).
TL;DR: In this paper, mixed matrix membranes (MMMs) composed of polyimide Matrimid ® and mesoporous silica spheres (MSSs) are prepared, characterized and tested in gas separation of equimolar mixtures H 2 /CH 4 and CO 2 /N 2 at different temperatures.
TL;DR: In this paper, the authors reported the crystallization of both α and γ-phase polyvinylidene fluoride (PVDF) films by varying preparation temperature using DMSO solvent.
Abstract: The γ-phase poly (vinylidene fluoride) (PVDF) films are usually prepared using dimethyl sulfoxide (DMSO) solvent, regardless of preparation temperature. Here we report the crystallization of both α and γ-phase PVDF films by varying preparation temperature using DMSO solvent. The γ-phase PVDF films were annealed at 70, 90, 110, 130 and 160°C for five hours. The changes in the phase contents in the PVDF at different annealing conditions have been described. When thin films were annealed at 90°C for 5 h, maximum percentage of β-phase appears in PVDF thin films. The γ-phase PVDF films completely converted to α-phase when they were annealed at 160°C for 5 h. From X-ray diffraction (XRD), Fourier transform infrared spectrum (FTIR), differential scanning calorimetry (DSC) and Raman studies, it is confirmed that the PVDF thin films, cast from solution and annealed at 90°C for 5 h, have maximum percentage of β-phase. The β-phase PVDF shows a remnant polarization of 4.9 μC/cm2 at 1400 kV/cm at 1 Hz.
TL;DR: In this paper, the water-reactivity of Al-Ga and AlGa-In-Sn alloys is investigated as a means to utilize the chemical potential energy of Al to split water for the production of H 2.
TL;DR: In this article, a natural plasticizer was synthesized in the laboratory by esterification of rice fatty acids and polyols, which was added to PVC and natural rubber latex films (5% w/w).
TL;DR: The crystallization of highly isotactic polypropylene confined in self-ordered nanoporous alumina is studied by differential scanning calorimetry to enhance the understanding of nanocomposites containing semicrystalline polymers and reveal design criteria for polymeric nanofibers with tailored mechanical and optical properties.
Abstract: The crystallization of highly isotactic polypropylene confined in self-ordered nanoporous alumina is studied by differential scanning calorimetry. A transformation from a predominantly heterogeneous to predominantly homogeneous nucleation takes place if the pore diameter is smaller than 65 nm. Crystallization is suppressed with decreasing pore size, and the absence of nucleation below 20 nm pores indicates the critical nucleus size. The results reported here might enhance the understanding of nanocomposites containing semicrystalline polymers and reveal design criteria for polymeric nanofibers with tailored mechanical and optical properties.
TL;DR: In this paper, a biodegradable composites were prepared with the modified rice straw fiber (MRSF) and poly(lactic acid) (PLA) by HAAKE rheometer.
TL;DR: In this paper, the thermal decomposition of citric acid, trans-and cis-aconitic acid has been studied using the TG-MS, TG-FTIR and DSC techniques.
Abstract: Thermal decomposition of citric acid, trans- and cis-aconitic acid has been studied using the TG-MS, TG-FTIR and DSC techniques. The measurements were carried out in an argon atmosphere over a temperature range of 293–673 K. The influence of the acid structures and configurational geometry on stability of the transition products and pathways of thermal transformations of the studied compounds studied is discussed.
TL;DR: The spray‐drying method was less dependent on the solubility characteristics of the drug when compared with traditional microencapsulation techniques such as phase separation or solvent evaporation techniques.
Abstract: Drug containing biodegradable poly(+/-)lactide microparticles were prepared by using a spray-drying technique. Formulations containing model drugs in either a dissolved (progesterone) or dispersed state (theophylline) were spray-dried. The spray-drying method was less dependent on the solubility characteristics of the drug when compared with traditional microencapsulation techniques such as phase separation or solvent evaporation techniques. Differential scanning calorimetry and scanning electron microscopy were used to characterize the microparticles. The drug release profiles were characterized by a rapid release phase (burst effect) followed by a slow release phase, the extent of each phase being dependent on the drug loading.
TL;DR: In this paper, the authors present a new twin-membrane calorimeter chip for fast differential scanning calorimetry (DSC) with the Flash DSC 1 of Mettler-Toledo.
TL;DR: In this article, the effect of the molar ratio of methanol to oil, reaction temperature, catalyst calcination temperature and catalyst amount used for transesterification were studied to optimize the reaction conditions.
TL;DR: In this paper, the authors investigated the effects of three-dimensional confinement on the glass transition temperature (Tg) of polymer nanoparticles under soft and hard confinement and quantitatively compared their results to those of thin films to explore commonalities or differences between the Tg-confinement effect for polymers confined to different geometries.
Abstract: When confined to the nanoscale, the glass transition temperature (Tg) of polymer films can deviate substantially from the bulk, i.e., the Tg-confinement effect. Due to ease of processing most studies have focused on the thickness-dependent Tg of thin films, while few have focused on extending investigations beyond thin films to other geometries. As polymers confined to higher geometrical dimensionalities become the enabling material in technologies ranging from drug delivery to plastic electronics to ultrafiltration, a greater understanding of size effects on the Tg is warranted. Here, we investigate the effects of three-dimensional confinement on the Tg of polymer nanoparticles under soft and hard confinement and quantitatively compare our results to those of thin films to explore commonalities or differences between the Tg-confinement effect for polymers confined to different geometries. Via modulated differential scanning calorimetry, we show that Tg decreases with size for polystyrene (PS) nanoparticl...
TL;DR: In this paper, the phase transition temperature of binary fatty acid and its corresponding mixing proportion are calculated with phase diagram thermodynamic method, and the results are verified by the experimental result of the heat absorption curve and the Differential Scanning Calorimetry (DSC) analysis curve.
TL;DR: In this paper, a new micro-PCM based on n-octadecane core and silica shell was synthesized through interfacial polycondensation in different conditions.
TL;DR: In this article, the effect of in situ synthesized 10nm silica nanoparticles on the glass transition and dynamics of natural rubber networks using differential scanning calorimetry, broadband dielectric relaxation spectroscopy and thermally stimulated depolarization currents.
TL;DR: In this article, five commercially available multi-walled carbon nanotubes (MWNTs), with different characteristics, were melt mixed with polycarbonate (PC) in a twin-screw micro compounder to obtain nanocomposites containing 0.25-3.0% MWNT.
TL;DR: In this article, a novel form-stable composite phase change material (PCM) for the latent heat thermal energy storage (LHTES) in buildings, passive solar space heating by impregnating of stearic acid (SA) into silica fume (SF) matrix through the technique of solution impregnation.
TL;DR: In this paper, the influence of glycerol/MMT loading on the nanocomposites morphology was studied by X-ray diffraction, Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and proton nuclear magnetic resonance (1 H NMR) measurements.
TL;DR: In this paper, a poly(methyl methacrylate) (PMMA)/graphene nanocomposites were prepared by in situ emulsion polymerization and Raman and Fourier transform infrared spectra showed that PMMA polymer contained partially reduced graphite oxide.
Abstract: Poly(methyl methacrylate) (PMMA)/graphene nanocomposites were prepared by in situ emulsion polymerization. Raman and Fourier transform infrared spectra showed that PMMA polymer contained partially reduced graphite oxide. Dynamic mechanical analysis and differential scanning calorimetry analysis showed that graphene in the PMMA matrix acted as reinforcing filler; it enhanced the storage moduli and glass transition temperatures of the nanocomposites. Thermogravimetric analysis showed that the thermal stability of the nanocomposites increased by ca . 35 °C. The electrical conductivity of nanocomposite with 3 wt.% graphite oxide was 1.5 S m −1 at room temperature.
TL;DR: In this paper, a facile surface-initiated-polymerization (SIP) method was used to construct polyaniline (PANI) nanocomposites reinforced with tungsten oxide (WO3) nanoparticles and nanorods (NRs).
Abstract: Polyaniline (PANI) nanocomposites reinforced with tungsten oxide (WO3) nanoparticles (NPs) and nanorods (NRs) are fabricated via a facile surface-initiated-polymerization (SIP) method. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) characterizations reveal the uniform coating of polymer on the filler surface and a good dispersion of the nanofillers within the polymer matrix. Unique negative permittivity is observed in pure PANI and its nanocomposites. The switching frequency (frequency where real permittivity switches from negative to positive) can be easily tuned by changing the particle loading and filler morphology. Conductivity measurements are performed from 50∼290 K, and results show that the electron transportation in the nanocomposites follows a quasi 3-d variable range hopping (VRH) conduction mechanism. The extent of charge carrier delocalization calculated from VRH well explains the dielectric response of the metacomposites. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) reveal an enhanced thermal stability of the nanocomposites with the addition of nanofillers as compared to that of pure PANI.