Vol 50, No 3 (2018)

Physicochemical aspects of modern technology for dissolution and spinning of wood cellulose solutions are discussed. The effects of the chemical structure of ionic solvents on the solubility of cellulose in them are analyzed.

Heat and moisture treatments were shown to affect restoration of the capillary-porous structure of paper folders that was lost during drying. Thermodynamic functions of cellulose water of hydration were calculated for hydrothermal treatment over broad ranges of time and temperature. The effects of saturated vapor with high state parameters on paper strength were demonstrated.

Structural transitions of Fe-containing fibrous and microcrystalline flax and hemp cellulose during heat treatment in an inert medium were studied using IR spectroscopy, x-ray diffraction, electron microscopy, thermogravimetric analysis, and N₂ adsorption. Mesoporous ferromagnetic graphitecontaining carbon composites with specific surface area 280-550 m²/g were produced. The nature and shape of the cellulose matrix and the iron-salt anion were found to affect the composition, shape, and size of metal particles and the catalytic graphitization process.

Cellulose powders from flax fiber and deciduous wood and hydrogels regenerated from DMA/LiCl solutions of them were studied using x-ray diffraction. Structural characteristics were calculated. Three-dimensional models of atomic positions in the short-range order of amorphous hydrogels were constructed. It was found that flax cellulose was characterized by a higher degree of crystallinity and larger transverse cross section and monofilament length than deciduous cellulose. Super-swelled and lyophilized hydrogels from the cellulose solutions gave diffuse diffraction patterns characteristic of amorphous materials. The calculated coordination-sphere radii for lyophilized hydrogels corresponded to analogous data for cellulose II. Differences in the coordination numbers were due to structural differences in the short-range order. The distribution of atoms in the short-range ordered region was modeled using molecular dynamics and corresponded to a disordered cellulose II cluster with dimensions along the crystallographic axes of 2a, 2b, and 5c (15, 16, and 52 Å). A cluster consisted of 16 cellulose chains ~52 Å in length.

Swelling of amorphous/crystalline polymers is a complex phenomenon, accompanied by a change in the internal energy of the polymer, the absorbate, and the solid solution, and also by transition of the polymer from the glassy state to the rubbery (high elasticity) state. The derivative of the internal energy (a thermodynamic characteristic of the solid solution) is the internal pressure. The excess internal pressure is the basic characteristic of the swelling process: the swelling pressure. We have analyzed the behavior of the change in swelling pressure, the common features and differences from swelling of gels and from osmotic phenomena.

Samples of carboxymethyl chitosan have been synthesized with different extents of substitution by changing the reaction conditions. Carboxymethyl chitosan completely dissolves in water when the extent of substitution exceeds 90%. The theological properties were studied for 4% aqueous solutions of carboxymethyl chitosan with CaCl₂ and Ca(OH)₂ as additives as well as for a mixture of carboxymethyl chitosan and polyethylene oxide with added CaCl₂. The introduction of additives to aqueous solutions of carboxymethyl chitosan leads to enhanced viscosity and gel formation.

A study has been carried out on the swelling of a copolymer of vinylidene fluoride and hexafluoropropylene in organic solvents. The optimal conditions for dissolving this fluoroelastomer were determined. Vulcanization of the fluorocopolymer was carried out using amine hardeners, namely, m-xylylenediamine and 3-aminopropyltriethoxysilane. A mechanism was proposed for the hardening of the copolymer. The effects of these hardeners on the coating properties were compared.

Oriented fibrous polymeric composite materials based on polyethyleneterephthalate, polypropylene, and polylactide matrices and fillers of various types and chemical nature were obtained by a melt technique. The effect of added fillers on the mechanical properties of the oriented composites was studied. It was shown that with the addition of various types of fillers there is an optimum concentration that leads to increase of the strength and rigidity in the oriented fibrous composite materials, and this is determined by the type and form of the disperse particles.

Modern methods of reconstructive–restorative surgery employing synthetic endoprostheses make it possible to improve substantially the results of surgical interventions. Here, as well as the operating technique the quality of the endoprostheses is also important. It is advisable to use mesh warp-knitted endoprostheses from biocompatible, bioresistant, hydrophobic, and non-capillary monofilaments not supporting inflammatory process in the wound and resistant to infection.

Many publications characterizing historical and technological aspects of activated carbon fiber production are reviewed. Issues with using various fiber precursors to produce sorbents are discussed. Solid-state activation, the search for new precursors, and the development of highly filled sorbents are identified as several applications of promising carbon-fiber adsorbent technologies.

Mathematical modeling and systematic analysis of viscoelastic processes in polymers are the basis for methods we have developed for computer-assisted prediction and qualitative analysis of polymer parachute cords. Solving the problem of qualitative analysis of deformation properties for parachute cords will let us improve the performance characteristics of domestic parachute systems and to improve their safety and functionality.

Light scattering and turbidimetry methods were used to study the self-assembly of macromolecules of eight-arm star-shaped poly-2-ethyl-2-oxazoline in aqueous solution. A sample with molecular mass 1100 g/mole was studied. The phase separation temperature for this polymer is higher than for stars with arms of poly-2-isopropyl-2-oxazoline, which is a consequence of the higher dehydration temperature of poly-2-ethyl-2-oxazoline. The star-shaped architecture and the presence of a hydrophobic calix[8]arene ring for this polymer were found to have hardly any effect on the low critical solution temperature.