Dynamic mechanical thermal analysis transitions of partially and fully substituted cellulose fatty esters

The main transitions of cellulose fatty esters with different degrees of substitution (DSs) were investigated with dynamic mechanical thermal analysis. Two distinct main relaxations were observed in partially substituted cellulose esters (PSCEs). They were attributed to the glass‐transition temperature and to the chain local motion of the aliphatic substituents. The temperatures of both transitions decreased when DS or the number of carbon atoms (n) of the acyl substituent increased. Conversely, all the transitions of fully substituted cellulose esters occurred within a narrow temperature range, and they did not vary significantly with n. This phenomenon was explained by the formation of a crystalline phase of the fatty substituents. The presence of few residual OH groups in PSCEs was responsible for a large increase in the storage bending modulus, and it eliminated the effect of n on damping. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 281–288, 2003     

Cellulose-based fibers from liquid–crystalline solutions. II. Processing and morphology of acetate/butyrate esters

Fibers were spun from isotropic and anisotropic dimethylacetamide solutions of cellulose esters. Take-up speeds of the dry jet/wet spinning process varied. Water served as the coagulant. The mechanical properties of the fibers increased as spinning progressed from the isotropic to the anisotropic state of the solution. A trade-off in solubility and fiber properties was noted as the butyryl acetyl ratio decreased. Whereas high butyryl content enhances both overall solubility and the formation of liquid–crystalline solutions at lower concentration, it results in lower fiber modulus and strength. Morphology of the fibers depended on the coagulation rate which was influenced by the concentration of the sppinning solution. The level of orientation and crystallinity of the fibers increased somewhat when they were spun from liquid-crystalline solutions. © 1993 John Wiley & Sons, Inc.     

The thermal decomposition of ammonium metavanadate

On heating, ammonium metavanadate (AMV) decomposes in several atmospheredependent stages. An important decomposition intermediate, ammonium hexavanadate (AHV), may also be prepared by wet-chemical methods and the kinetic parameters for the thermal decomposition of AMV and of the AHV preparation have been obtained. The kinetic study has been supplemented by surface-area measurements and by electron microscopic examination of the surfaces of reactant, intermediate and product crystallites. On the basis of the type of decomposition curve, the measured activation energies, and the effects of oxygen and water vapour on the decomposition rate, it has been concluded that in vacuum and in inert atmospheres the evolution of ammonia is the rate-determining step, while in oxidizing atmospheres evolution of water is rate determining. Comparison of the kinetic parameters with thermodynamic data for the decomposi. tion has led to suggestions as to the nature of the activated complexes involved.