L. V. Ganina

The thermal decomposition of hexamethylenetetraammonium dodecahydro-closo-dodecaborate

The kinetics and products of the thermal decomposition of hexamethylenetetraammonium dodecahydro-closo-dodecaborate in air, argon, and a vacuum were studied using thermogravimetry, volumetry, mass spectrometry, and IR spectroscopy. According to the nonisothermal kinetic data, noticeable rates of the formation of volatile products were observed at temperatures higher than 150°C. The thermal decomposition of the salt occurred in stages. At 160–200°C, the thermal decomposition of hexamethylenetetraammonium dodecahydro-closo-dodecaborate could not be described by simple kinetic equations. The dependence of the initial reaction rates on inverse temperature (lnV0−1/K) was linear, which showed that the thermal decomposition of the salt obeyed the Arrhenius equation V0 = 109.4 ± 0.6exp[(−20500 ± 1800)/RT], %/min. The obtained temperature dependences of the kinetic parameters of thermolysis were used to predict the time of salt storage and the conditions of work with it. A comparison of the kinetics of the thermolysis of hexamethylenetetraammonium dodecahydro-closo-dodecaborate and free hexamethylenetetraamine in open and closed reaction systems showed that the thermolysis of hexamethylenetetraammonium dodecahydro-closo-dodecaborate was not accompanied by salt dissociation to hexamethylenetetraamine and dodecahydro-closo-dodecaborate acid. The products of its thermolysis volatile under normal conditions were trimethylamine with a small admixture of nitrogen. The solid residue after thermolysis was a high-porosity insoluble product, whose volume was 6–8 times larger than the volume of the initial sample. An analysis of the IR spectra of the solid thermolysis product showed that it had a well-defined salt character. The special features of the IR spectra of initial hexamethylenetetraammonium dodecahydro-closo-dodecaborate and the product of its thermolysis led us to suggest that an acid-base equilibrium of the type [R3N-H+] + A ↔ [R3N… H+…A] occurred in it and, probably, in the initial salt. Here, R3N is the tertiary amino group, and A is the borohydride acid residue. Indications of amorphization allowed us to suggest that polymer structures were formed as a result of intramolecular interaction between the borohydride anion and onium cation.

Phase equilibrium in the diglycidyl ether of bisphenol A–hydroxyl-terminated oligobutadiene derivatives systems

The phase equilibrium in the binary systems based on hydroxyl-terminated butadienes and diglycidyl ether of bisphenol A has been studied in wide ranges of temperature and compositions of the solution. The analysis of the obtained experimental and calculated data shows that the molecular weight, content of hydroxyl groups, functionality of the oligomer, and the presence of bromine in the oligomer affect the level of the thermodynamic compatibility. An increase in the content of hydroxyl groups and bromine results in an increase in the compatibility of the components. The results obtained are interpreted in terms of the Flory-Huggins theory. The correlation between the phase boundary concentrations and an upper critical solution temperature and solubility parameters of the oligobutadienes has been established.

Thermodynamic properties of chitosan dodecahydro-closo-dodecaborate

Combustion enthalpies of chitosan dodecahydro-closo-dodecaborate corresponding to −13194 kJ/mol are measured via combustion in an AKS-3M automatic calorimeter. The standard enthalpy of formation corresponding to −5223 kJ/mol is calculated from the resulting experimental data.

Mutual diffusion and phase equilibrium in copolymers of nonyl acrylate and acrylic acid-diglycidyl ether of bisphenol A systems

The influence of the composition of statistical copolymers of nonyl acrylate with acrylic acid on the rate of mass transfer and phase equilibrium in solutions with diglycidyl ether of bisphenol A was studied. For these systems, the data on concentration dependencies of mutual diffusion coefficients and phase diagrams were obtained. The results were interpreted on the basis of the assumption about the effect of the effective concentration of nodes of the network of hydrogen bonds on the mutual diffusion and phase equilibrium. The dependencies of the mutual diffusion coefficients on the content of acrylic acid in the copolymers are described in terms of the free volume theory.

Impact sensitivity of energy systems based on nanoporous silicon and oxidant: influence of the hydrogen content and specific surface

The impact sensitivity of the energy systems based on nanoporous silicon, obtained by electrochemical etching of monocrystalline silicon wafers in an HF-containing electrolyte, and calcium perchlorate was studied using a modified Weller—Ventselberg technique (estimation of the impact sensitivity of initiating explosives). The impact sensitivity of these systems is shown to be determined by both the presence of hydrogen, which is stored on the porous silicon surface during the preparation of the latter, and also the influence of other factors, including the specific surface of porous silicon. The composition, amount of the generated gas, and gas evolution rate during nonisothermal and isothermal calcination of porous silicon in a temperature range of 60—120 °С were determined using methods of thermal gravimetry (TG), measurement of the gas volume, and mass spectrometry. The generated gas almost completely consists of hydrogen, and its content in the studied samples of porous silicon achieved ~3.8 wt.%. The calculated activation energy of the hydrogen evolution process in vacuo was 103.7±3.3 kJ mol–1. The dependences of the impact sensitivity of the energy composition based on porous silicon and heat of combustion of porous silicon on oxygen on the hydrogen content were established. The impact sensitivity of the energy system decreases with a decrease in the hydrogen content in porous silicon and its specific surface.

Interdiffusion and phase equilibrium in systems based on cellulose nitrates and low-volatile solvents

Phase equilibrium and interdiffusion in systems based on cellulose nitrates with different contents of nitrogen and several organic solvents, such as ethyl carbitol, dimethyl carbonate, and diethyl carbonate, have been studied. Cellulose nitrate containing 12.2 wt % nitrogen forms homogeneous systems with all studied solvents over the entire composition range. Systems based on cellulose nitrate with a high content of nitrogen (13.2 wt %) possess limited compatibility with the solvents. Phase diagrams constructed for these systems testify to the fact that the region of homogeneous solutions widens with a decrease in temperature. For the system composed of cellulose nitrate containing 13.2 wt % nitrogen and ethyl carbitol, the lower critical mixing temperature is −10°C. The presence of water in ethyl carbitol causes widening of the region of unstable solutions and leads to a reduction in the lower critical mixing temperature.

Effects of phase equilibrium and the rate of mutual dissolution of reactants on the formation of polyurethane block copolymers

Interdiffusion and phase equilibrium in the region of amorphous separation were investigated by means of the microinterference technique at 20–130°C for a number of binary systems based on oligoesterdiol, butanediols, and diisocyanates—components of polyurethane block copolymers. The concentration dependences of interdiffusion coefficients in the mutual dissolution region were determined for all test systems. For systems composed of partially compatible components, the concentration limits of thermodynamically unstable solutions were established. By means of transmission electron microscopy, the structure of polymers synthesized both in the region of single-phase solutions of the reactants and in the phase separation region is assessed.

Phase equilibrium and diffusion in binary systems based on nonyl acrylate, acrylic acid, and their homo- and copolymers

The phase equilibrium and diffusion in systems based on nonyl acrylate, acrylic acid, and their homopolymers and copolymers of different compositions have been studied in the range of 20–100°C by the microinterference technique. For the systems with the limited solubility of components, the phase diagrams have been constructed. It has been established that, with a rise in the content of carboxyl groups in the copolymers, the diffusion coefficients and the thermodynamic compatibility of the monomers decrease. It is suggested that the nonlinear pattern of a variation in the diffusion coefficient with the content of acrylic acid in the copolymers is predominantly associated with a change in the type of hydrogen bonds and the formation of carboxyl dimers upon the transition to poly(acrylic acid). The concentration of carboxyl groups may serve as a parameter indicating variations in thermodynamic compatibility and diffusion constants of the monomers with the intensity and type of hydrogen bonds in the polymers under study. The presence of hydrogen bonds and their type are estimated on the basis of the IR spectra of the homo- and copolymers of interest.

Thermodynamic Properties of Hexamethylenetetrammonium Dodecahydro-closo-dodecaborate

The enthalpy of combustion of hexamethylenetetrammonium dodecahydro-closo-dodecaborate is determined via combustion in a KL-5 calorimeter and is found to be‒17660 kJ/mol. Its standard enthalpy of formation is calculated using the obtained experimental data (−538 kJ/mol).

Mutual diffusion and phase equilibrium in the polysulphone-solvent type systems☆

Phase equilibrium and mutual diffusion have been studied in the polysulphone-solvent type systems. Investigations were conducted within the temperature interval 20–110°C with a wide range of solution concentrations, taking DMSO, chlorobenzene, nitrobenzene, N-methyl-2-pyrrolidone and chloroform as solvents. Only DMSO proved to be partially compatible with polysulphone. The phase equilibrium diagram was constructed for this system. The presence of moisture in DMSO has a marked effect on the position of the binodal: if the moisture in the solvent is increased to 1.3 wt% the upper critical consolute temperature (UCCT) is displaced by ∼30°C and the labile solution region is widened. The concentration dependences of the coefficients of mutual diffusion were obtained for the studied systems. The effect of moisture in DMSO on the mutual diffusion coefficients is revealed.