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for water is 334 J g −1 . The heat of crystallization (Δ H c ) is the result of the change in the phase of water from liquid to a solid, which occurs at the crystallization temperature ( T c ). Heat of crystallization for water is 334 J g −1 . The
Abstract
The thermal analytical study of most hydrophobic and hydrophilic D/L amino acids reveals significant hydropathy index correlation between the presence of water and crystalline amino acids. The TG derivative mass profiles for arginine and lysine (hydrophilic acids) at various time intervals of atmospheric exposure, show two distinct peaks, one between 50 and 60°C (unbound water), and one close to 100°C (bound-like water). The DSC heat-cool profiles for lysine and arginine confirmed the presence of these multiple waters with two heats of vaporization. The absence of these patterns from the TG and DSC for cysteine and phenylalanine (hydrophobic acids) further supports the conclusions.
Abstract
Crystallization behaviour of the amorphous Bi0.96Pb0.24SrCaCu1.6O5+x (0<x<1), obtained by rapidly quenching the melt, has been investigated by the differential thermal analysis (DTA) method under different atmosphere e.g. Ar, air, O2 and vacuum. Crystallization temperatures, activation energies and heat of crystallization are found to be 708–728 K, 2.25–2.32 eV and 0.16–1.81 kJ/g-atom, respectively, depending upon the atmosphere used during DTA. This material undergoes a number of structural and thermochemical transformations on continuously heating during DTA upto the melting temperature, which depends critically upon the atmosphere used.
Abstract
The non-isothermal crystallization and melting of ultra high molecular weight polyethylene (UHMWPE) were observed by means of differential scanning calorimetry and compared with those of ordinary high-density polyethylene (HDPE). The crystallization temperature (T c ) and melting point (T m ) of UHMWPE were found to be higher thanT c andT m of HDPE, and the latent heat of crystallization (δH c ) and fusion (δH m ) of UHMWPE are smaller thanδH c andδH m of HDPE. The results were explained in terms of the theory of polymer crystallization and the structure characteristics of UHMWPE. The relationships between the parameters (T c ,T T ,δH c andδH m ) and the molecular weight (M) of UHMWPE are discussed. Processing of the experimental data led to the establishment of four expressions describing the above relationships.
The enthalpies of solution in 2 N nitric acid at 298 K were measured for alkali metal borate glasses and crystals. From the data obtained, their enthalpies of formation from the oxides and the heats of crystallization of the glasses were calculated.
0 of the regression line ( Fig. 9 ), confirmed that the method was accurate and sensitive. The slope of 0.415 (expressed as J/g·%) corresponds to the specific heat of crystallization (41.5 J/g), which was obtained by testing the 100% amorphous
.18 The heat of crystallization is related to composition of blends which is tabulated in Table 2 and it decreases continuously with increase in ML proportion. The changes in crystallization peak width and heat of crystallization indicate that in case of
decrease in the heat of crystallization of HDPE ( Table 4 ) in these blends. These features could be tentatively explained as follows. During melt-mixing in the Brabender, the amorphous content was able to selectively dissolve a certain amount of the more
Heat of crystallization Calorimetric measurements The isothermal crystallization behavior of PBN, PDEN, and PTDEN was investigated with a Perkin-Elmer DSC7 calorimeter. The external
released in the total heat released (crystallization enthalpy), the amount of precipitated wax at different temperatures can be determined by dividing the accumulated heat released by the heat of crystallization as has been reported in literature [ 7 , 8
