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Abstract  

Several samples of terfenadine prepared by crystallization from different solvents under different experimental conditions were studied. The DSC curves obtained at a heating rate of 1C min−1 afforded the temperature of melting and the mole fractions of the components of each sample. Certain of the samples were composed of two solid phases mixed in molar ratios varying between nearly one and a single structural form. Three polymorphic forms were identified.

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Abstract  

Terfenadine samples prepared by crystallization in different media and supersaturation conditions were used to investigate the polymorphism of the substance. The study was based on DSC melting curves. An empirical parametric equation was used for modelling the experimental data. The signal recorded was resolved into the corresponding overlapping peak components by fitting analysis. Four polymorphic phases were identified.

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Abstract  

The example of polyethylene of low density (PELD) crystallization in ethylbenzene and some other alkylbenzenes presence demonstrates the unsufficiency of formal liquidus curve knowledge for the description of phase equilibrium in amorphous-crystalline polymer-liquid system. Experimental data affirming polymorphous structure of PELD crystalline phase and influence of the solvent on the order of various regular structures formation in it are being reported.

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4MP1 crystallized at different cooling rates; b DSC melting curves at 10 K min −1 from 323 to 523 K of P4MP1 crystallized at different cooling rates Table 1 DSC data

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Abstract  

It is shown that for porous systems filled with a solvent, if the temperature domains of crystallization and melting of the solvent are well separated, DSC technique, combined with suitably chosen thermal cycles, provides crystallization and melting curves which are independent of a) the mass of the material, b) the thermal contact between DSC pan and material and c) the thermal conductivity of the material. This method called DSC fractionation is applied to butyl rubber containing small water nodules. Thermoporosimetry is then applied to get the size distribution of mesoscopic solvent droplets.

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Comparative analysis of several methods for purity determination using DSC is presented. This is based on a mathematical model including the construction of theoretical melting curves for two-component systems and the calculation of recorded melting curves with the help of a set of equations describing the formation of a DSC output signal. It is shown that the true accuracy of purity determinations in the range of impurity concentrations ¯x=0.005–0.02 does not exceed 30–50%.

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DSC purity determinations have become very popular today [3]. The latest edition of the Mettler software package for thermal analysis, TA72.S GraphWare, now comprises a powerful purity evaluation program. It is based on the simultaneous calculation of the mole ratio of the sum of the eutectic impurities, the melting point of the pure component, the melting point of the substance present and the linearization term. The portion of the melting curve investigated is selected appropriately.

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Abstract  

The melting process of constrained nylon 6 fibers has been studied to estimate the true melting point of its original crystals. The melting peak became simpler in shape and shifted to higher temperature with increasing fiber-axis restricting force. When heating rate, β, was increased, the temperature where the melting curve initially departs from its baseline, Tsm, decreased steeply in the range of 45 to 60C min-1, and increased linearly with increasing β above 60C min-1. By linear extrapolation of Tsm to 0C min-1, the temperature of ca 190C was obtained for the melting temperature of the original nylon 6 crystals. This seems to correspond to the zero-entropy-production melting of the most imperfect crystallites of the nylon 6 fabric.

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Abstract  

The physical–chemical properties and fatty acid composition of sheep subcutaneous, tallow, intestinal, and tail fats were determined. Sheep fat types contained C16:0, C18:0, and C18:1 as the major components of fatty acid composition (19.56–23.40, 20.77–29.50, 32.07–38.30%, respectively). Differential scanning calorimetry (DSC) study revealed that two characteristic peaks were detected in both crystallization and melting curves. Major peaks (T peak) of tallow and intestinal fats were similar and determined as 31.25–24.69 and 7.44–3.90 °C, respectively, for crystallization peaks and 15.36–13.44 and 45.98–44.60 °C, respectively, for melting peaks in DSC curves; but those of tail fat (18.29 and −2.13 °C for crystallization peaks and 6.56 and 33.46 °C for melting peaks) differed remarkably from those of other fat types.

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Abstract  

The crystalline phase of dimyristoylphosphatidylethanolamine (DMPE)-water system was obtained by annealing the gel phase at around −5°C for periods up to 30 days. It was investigated by differential scanning calorimetry and negative-stain electron microscopy, particularly focusing on the behavior of water molecules. The crystalline phase showed a two-dimensional ribbonlike structure composed of regularly-stacked lamellae with an interlamellar spacing narrower than that of the gel phase. The conversion of the gel to crystalline phases on annealing was accompanied by a change in the bonding model of water molecules from a loosely-bound interlamellar water to a more loosely-bound water outside the lamellae. Ice-melting curves were deconvoluted using a computer program and different structures of water were estimated from enthalpy changes of each deconvoluted component. In accordance with a micrograph, only the loosely-bound water of one molecule of H2O per lipid was shown to be located between lamellae of the crystalline phase.

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