High-temperature aging of Halar film. II. Analysis of melting behavior

Melting behavior of an experimental Halar film, a predominantly alternating 1:1 copolymer of ethylene (E) and chlorotrifluoroethylene (CTFE), has been studied. Differential scanning calorimetry (DSC) reveals single or double melting peaks, depending upon the thermal history. The lower-temperature melting peak T_m1 is produced only by the thermal treatment and shows a strong dependence on annealing time and temperature. On the basis of the DSC and x-ray data it can be suggested that T_m1 represents the melting of relatively small crystallites formed upon annealing. The higher-temperature melting peak T_m2 is always shown at 238°C. (Note: the specification for commercial Halar product is 240°C. The slightly lower melting temperature reported in this study is probably due to the fact that we are dealing with an experimental melt-processed material.) On the basis of the heating rate study we propose that Halar crystallizes with stable crystals (T_m2 = 238°C) regardless of the crystallization conditions, i.e., quenching, slow cooling, or even annealing. Crystals of Halar have a heat of fusion of approximately 35 cal/g or 146 kJ/kg. Detailed analysis of the melting behavior of Halar is presented.     

Electrical resistivity of noble and transition metals using Animalu's model potential

Calculations of the electrical resistivity of several solid noble and transition metals have been carried out using the transition metal model potential proposed by Animalu. It has been found that, except for Cu, Ag and Au, the calculated resistivities of solid transition metals are considerably below the experimental values indicating that the Animalu's model potential fails to account for the electrical resistivities of transition metals. The failure of the Animalu's model potential has been discussed.     

Studies of coupled molybdate and tungstate vibrations

The polarized Raman and infrared reflection spectra of molybdate and tungstate compounds of barium and strontium are presented and analyzed. The longitudinal and transverse frequencies of the infrared active phonons were calculated by a Kramers-Kronig analysis of the reflection curves. A strain induced forbidden mode was observed in the reflection spectra that gives interpretation of the strong shoulder on the ν₃ bands in the absorption spectra of mulled samples. The correlation field splittings of the internal modes were analyzed in terms of dipole-dipole interaction theory. The correlation field splittings of the ν₃ modes were found to be explainable in terms of dipolar coupling alone, while the splittings of the ν₂ and ν₄ modes could not be accounted for in terms of dipolar coupling.     

Diffuse x-ray scattering near Bragg peaks from point defects in a general lattice

Using the continuum theory of linear elasticity, diffuse x-ray scattering has been calculated in the immediate neighbourhood of Bragg peaks from point defects in a lattice containing more than one atom in the unit cell. General expressions are obtained for the Debye-Waller factor, Huang diffuse scattering and the asymmetric scattering due to the defect. For lattices with one atom per unit cell, these expressions reduce to the well-known formulae of diffuse scattering.     

Acid catalyzed condensation of isoprene with orcinol: Synthesis of 2,2-dimethylchromans and 5-methylxanthyletin derivatives

Condensation of orcinol with 2-methylbuta-1,3-diene (isoprene) has been achieved in the presence of orthophosphoric acid as catalyst leading to the exclusive formation of 2,2-dimethylchromans in one step. A novel route for the synthesis of 5-methylxanthyletin derivatives is described.     

Performing solvation free energy calculations in LAMMPS using the decoupling approach

Journal of Computer-Aided Molecular Design - The decoupling approach to solvation free energy calculations requires scaling the interactions between the solute and the solution with all...     

Highly dispersed clay-polyolefin nanocomposites free of compatibilizers, via the in situ polymerization of alpha-olefins by clay-supported catalysts

In situ polymerization by certain transition metal catalysts supported on and activated by acid-treated montmorillonite produces well-dispersed clay-polyolefin nanocomposites, without requiring either organic surfactants to be present in the clay phase or modification of the polyolefin structure.