V. M. Buznik

IR-spectroscopic examination of polytetrafluoroethylene and its modified forms

The results of IR-spectroscopic examinations of the molecular and supramolecular structure of polytetrafluoroethylene and polymer materials thereof were summarized. It was shown that, upon heat, mechanical, and other treatment, as well as under radiation exposure, polytetrafluoroethylene preserves its chain-helical conformation, and the resulting modified forms consist of crystalline and amorphous phases in a ratio depending on the history of the sample. The degree of the structural ordering in the polymer decreases with increasing temperature and pressure. The formation of branched moieties and short macromolecules with double bonds (−CF=CF2) in the terminal groups is specific for the process caused by thermal and radiation-induced degradation. The oxidation of the polymer macromolecules requires applying high irradiation doses and heating samples in an oxygen or air atmosphere.

Quantum-chemical calculations of the IR absorption spectra of modified polytetrafluoroethylene forms

DFT(B3LYP) (basis set 6–31 + G(d)) and HF (basis set 6–31G) calculations were performed to determine the geometric structure and vibrational spectra of the CnF2n and CnF2nO molecules (n = 3–13). The IR spectra of chain CnF2nO molecules with the terminal carbonyl group (-COF) were found to contain a band at 1885 cm−1. The C=C and C=O stretching vibrations of the-CF=CF2 and COF terminal groups were independent, and there was no mutual influence of their frequencies starting with the seven-fragment molecule. In the presence of chain branching, the sensitivity of the ν(C=C) and ν(C=O) frequencies in the olefin and carbonyl groups depended on where branching occurred. The chain configuration was found to be energetically favorable compared with branched structures.

Radiation-chemical synthesis of tetrafluoroethylene telomers and their use for preparation of thin protective fluoropolymer coatings

The specific features and possibilities of preparation of protective coatings and composite materials based on fluoromonomers using high-energy rays (60Co γ-rays, fast electrons) were analyzed. The emphasis was placed on synthesis and application of tetrafluoroethylene telomers in acetone. The structure and properties of telomers were examined by IR and NMR spectroscopy, as well as by X-ray diffraction analysis and diathermy. The radiation initiation allows preparation of new products with a broad spectrum of functional properties and opens wider prospects for technological application of fluoromonomers.

Imparting enhanced hydrophobicity to polyester fabrics: Formation of ultrathin water-repelling coatings on the fiber surface

A new technology for hydrophobization of synthetic fiber materials was described. This technological approach is based on formation of nanosized fluoropolymer coatings from solutions of low-molecularweight fraction of ultradispersed polytetrafluoroethylene and tetrafluoroethylene telomers. The mechanism of formation of protective coatings was described, and the properties of polyester materials thus modified were presented.

Fluoropolymer chemistry in Russia: Current situation and prospects

The current situation in the fluoropolymer chemistry and industry in Russia was overviewed, including the fluoropolymer manufacture and market related issues. Also, the research and manufacturing cooperation in the framework of the “Fluoropolymer Materials and Nanotechnology” joint venture was discussed.

Effect of bismuth trifluoride on the characteristics of fluoroindate glasses : The InF3-BiF3-BaF2 system

Glass formation in the InF3-BiF3-BaF2 system is studied. Partial substitutions of BiF3 for InF3 in the InF3-BaF2 system reduce the glass-transition and glass-crystallization temperatures and increase the thermal stability range and refractive index. The glass structure is studied using IR and Raman spectroscopy. InF6 and BiFn polyhedra are identified in the system. Doping the glass with bismuth trifluoride changes the degree and linkage character of the InF6 polyhedra in the glass network. The medium-range order length is not affected by the bismuth trifluoride concentration in the glass. The modifier cation (Ba2+) substantially determines the correlation length in the glasses.

Morphology and structure of micro- and nanosize polytetrafluoroethylene powders prepared by the gas-phase method

Formation of fluoropolymer nanoaerosols and micropowders in the gas products of polytetrafluoroethylene pyrolysis and the hierarchical self-organization of ultradispersed powders were revealed. The features of the molecular and supramolecular structures of powders were analyzed. Low- and high-molecular-weight fractions of the fluoropolymers, constituting the powder particles were identified, and a method for their partitioning was proposed.

Structure and properties of oxofluoroniobate glasses based on MnNbOF5

The MnNbOF5-BaF2 and MnNbOF5-PbF2 systems have a wider glass region than the binary system NbO2F-BaF2. According to thermogravimetric analysis data, the glasses in these systems are characterized by lower glass transition temperatures than the similar binary glass 50NbO2F·50BaF2. The thermal stability range and the degree of thermal stability of the glasses depend on the modifying cation. As demonstrated by IR and Raman spectroscopy, the glass structure is built from Nb(O,F)6 polyhedra linked into a glass network by oxygen and fluoride bridges. This is explained by the fact that the starting component MnNbOF5·4H2O decomposes to NbO2F upon melting. The manganese cations form their own polyhedra, which are incorporated into the glass network. The modifying cations exert a considerable effect on the glass network structure and on short-and medium-range order domains.

Hexamethylenetetrammonium dodecahydro-closo-dodecaborate: Synthesis and study

The reaction of dodecahydro-closo-dodecaboric acid with hexamethylenetetramine (urotropin) was studied by potentiometric titration, chemical and X-ray diffraction analyses, thermogravimetry, and IR and X-ray photoelectron spectroscopy. The donor-acceptor bond with acid H+ cations involves only one of the nitrogen donor atoms of hexamethylenetetramine. The product (C6H12N4H)2B12H12 is isolated as a finely crystalline, easily filterable, and poorly soluble precipitate. A saturated solution of the product contains no more than 0.4 g of the salt per 100 g.

Glasses in the CuNbOF5-BaF2 and CuNbOF5-PbF2 systems

Nonhygroscopic, colored glasses have been synthesized in the CuNbOF5-BaF2 and CuNbOF5-PbF2 systems proceeding from crystals of the complex compound CuNbOF5 · 4H2O. The glasses have been studied structurally and thermally. The crystallization resistance of the glasses has been studied as a function of glass composition. Lead difluoride glasses are more stable than barium difluoride glasses of the same composition. These glasses have lower glass-transition temperatures than the binary glasses formed in the NbO2F-BaF2 system. The glass structure is built of Nb(O,F)6 polyhedra, which are linked in glass networks through oxygen bridges. Modifier cations influence both the structure of glass networks and the linkage of polyhedra.