Variable temperature polymers

The phase behavior of polybibenzoates has been investigated mainly by DSC, variable-temperature x-ray diffraction, and optical microscopy. However, only the first two techniques are useful in the case of polymers with the high-molecular weights required for materials with good mechanical properties and, in such cases, revealing textures are not usually observed by optical microscopy. 

The results of research into the fluidised bed pyrolysis of plastic wastes are reported, with reference to determining the optimum process conditions for the process with respect to the reactor behaviour. The study investigates the effects of process variables such as bed temperature, polymer feed rate, bed hold-up, fluidising velocity, and size of inert material. Findings illustrate the importance of the knowledge of the hydrodynamics of the fluidised bed and of the interactions between bed and polymer particles in the design and operation of the reactor. 15 refs. 

Ivanov, D.A. and Magonov, S.N., Atomic Force Microscopy Studies of Semicrystalline Polymers at Variable Temperature, in Polymer Crystallization Observations, Concepts and Interpretations, Sommer, J.-U. and Reiter, G., Eds., Springer, Heidelberg, Germany, 2003, chap. 7. 

D.A. Ivanov and S. Magonov, Atomic force microscopy studies of semicrystalline polymers at variable temperature. In G. Reiter, J.-V. Sommer (Eds.), Polymer Crystallization, Springer, Berlin, 2003, p. 98. 

In general, then, an examination of the effects of the operational variables temperature and frequency and of changes in the nature of the polymer is closely tied ty) TK and which set the location of the transition zone in plots such as Figure 5B and A, respectively. 

Excipients 13C, 25Mg, 23Na Determination of the degree of cross-linking for polymer systems, drug-excipient interaction studies (variable temperature), (pseudo)polymorphic characterization at the qualitative and quantitative level... 

NMR spectra and Tj measurements at different temperatures. The local polymer chain motion varies over a frequency range of 104-106 Hz in the nematic phase. The activation energy of this motion is found to increase with decreasing number ( ) of methylene units in the spacer, and exhibits odd-even fluctuations. In a study of a homologous series of main-chain LC polyesters, 13C CP/MAS and variable-temperature experiments reveal a conformation-ally more homogeneous and a less dynamic nature for the even-chained than for the odd-chained polymer structures.300... 

Variable temperature measurements were carried out on a Varian A-60 spectrometer with a Varian-4060 probe heater attachment. Probe temperatures were calibrated with a standard ethylene glycol sample. Samples were prepared by dissolving up to 25 per cent by weight of polymer in tetrachloroethylene. Even with such concentrated solutions no viscosity problem was encountered above 60°. 

Garroway, Ritchie, and Moniz 70 continued the characterization of epoxy polymers with respect to molecular motion using variable temperature, solid state C-13 NMR. DGEBA was the epoxy of interest. The DGEBA was cured with piperidine, m-phenylene diamine, hexahydrophthalic anhydride and nadic methyl anhydride. The piperidine cured DGEBA had the best resolved polymer spectra. This system... 

We demonstrate that the physical properties of Xe adsorbed in mesoporous MCM-41 molecular sieves can be deduced from the analysis of the variable temperature l2,Xe NMR chemical shift data. For example, the interactions between the adsorbed Xe and the wall of the adsorbent, 8S. Our results indicate that the interactions arise from Xe adsorbed in mesoporous MCM-41 deviates significantly from not only the bulk Xe, but also from Xe adsorbed on microporous adsorbents or polymer surfaces. At a given temperature T, the pore size dependence of 8S can be described by the empirical relation 8,(T, d) = A(T)/(d + B(T)). The two temperature-dependence parameters were expressed by polynomial functions whose temperature coefficients were also revealed explicitly to the second order. 

Variable-Temperature Magic-Angle Spinning Carbon-13 NMR Studies of Solid Polymers... 

In this section, initial spectral data on several polymers are reported to illustrate the utility of variable-temperature magic-angle spinning (VT-MAS) for the study of macromolecules in the solid state. 

From the viewpoint of polymer applications, the full exploitation of the combined resolution/sensitivity enhancement techniques to obtain "high-resolution" spectra of rare-spin nuclei in solids requires variable temperature spinning capability. In this paper, we describe briefly a spinner assembly suitable for routine operation over a wide range of temperature at the full complement of spinning angles and report - C spectral data at low temperature on several polymers, including fluoropolymers. In addition, variable temperature spin-lattice and rotating frame relaxation times are reported for isotactic poly(propylene). 

Poly(dioctyl)stannane and poly(dihexyl)stannane exhibit a reversible thermochromic behaviour as a result of a phase transition at ca 40 °C. A discolouration of the polymers was observed upon slightly warming above room temperature and variable-temperature UV-vis spectrometry showed a reduction of the >.max values of (n-Oct2Sn) in toluene solution from 384 to 369 nm and of (n-Hex2Sn) from 398 to 382 nm82. On the other hand, however, poly(dibutyl)stannane and poly(diaryl)stannane do not exhibit thermochromic behaviour in the temperature range between —10 to 90 °C and —20 to 90 °C82 100, respectively. 

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