Composite materials based on fluoropolymers and oxyfluoride glasses

It was shown that molded specimens of polymer composite materials can be obtained by an extrusion method by melt blending of Fluoroplast F-2 MB (modified poly(vinylidene difluoride)) and oxyfluoride glasses of the composition 3B₂O₃ (40SnF₂–30SnO–30P₂O₅). The compositions of the observed phases of the composites were determined. Conclusions were made on the incompatibility of the components, their dispersion distribution, and strong adhesion interaction. Data on the nano level of the blending of the components were obtained. The elongation and Brinell hardness were measured in the composites with various (0–50 vol %) oxyfluoride contents. It was concluded that it is possible to produce composites based on fluorinated hydrocarbon and fluoroxide polymers.     

Polymeric nanocomposites based on fluoropolymers and nanocarbon from detonation synthesis

The effect of modifying additions of nanocarbon from detonation synthesis on the physicomechanical properties of fluorinated copolymers derived from vinylidene fluoride was examined.     

Heat capacity of fluoropolymers

The heat capacities of poly(vinyl fluoride), poly(vinylidene fluoride), and polytrifluoroethylene have been measured between 80 and 340°K. The results can be expressed as the sum of two terms: the optical contribution calculated from the vibrational band assignments in the literature and the acoustical contribution calculated according to the Tarasov continuum model. Combining our data with those for polyethylene and polytetrafluoroethylene, it is concluded that the force constant for one-dimensional intrachain interaction is approximately constant for all polymers with carbon backbones. The force constant for three-dimensional interchain interaction is one order of magnitude smaller than the one-dimensional force constant, and decreases when the hydrogen atoms in polyethylene are replaced by fluorine atoms. The thermodynamic functions for the three polymers have been evaluated. Glass transitions at 228°K and 305°K have been found in poly(vinylidene fluoride) and polytrifluoroethylene, respectively.     

High-temperature aging of fluoropolymers

Fluoropolymers including those of 3,3,3-trifluoropropene, 2,3,3,3-tetrafluoropropene, 3,3,4,4,5,5,5-heptafluoropentene-1, and their copolymers with tetrafluoroethylene, were aged in air and in its absence at 225 and 305°C. Intrinsic viscosities were measured before and after aging. Polymers of high tetrafluoroethylene content are most stable. In air the presence of tertiary hydrogens is associated with lowered stability but the presence of tetrafluoroethylene greatly mitigates this effect. Stress-relaxation studies in air of a vulcanizate of 3,3,3-trifluoropropene and tetrafluoroethylene cured by γ-rays indicate that the vulcanizate degrades much more rapidly than the untreated polymer.     

Bibliometric analysis of scientific publications on fluoropolymers

Scientific publications on fluoropolymers are sought in the Chemical Abstracts Plus database accessed via the SciFinder system. For the period 1946–2010, nearly 116 000 publications containing the search term fluoropolymers as the main concept are found. For nearly 75 000 publications over the period 2000–2009, a detailed bibliometric analysis is performed on the basis of thematic sections and subject headings of the database, substances, publication types, languages and authors of publications, journal titles, and organization names. On the basis of the results, recommendations for improving Russian indicators in the field of fluoropolymers are suggested.     

A challenge to novel fluoropolymers

Perfluoro(vinyl ether) derivatives are extremely versatile monomers in preparing a variety of functional fluoropolymers. In this paper, two challenging topics in the development of novel fluoropolymers will be introduced. Carboxylated perfluoro(vinyl ether) can be copolymerized with tetrafluoroethylene to afford perfluorinated ion-exchange membranes, which realize the innovative process for pollution-free and energy-saving chlor-alkali production. Another topic includes the discovery of selective cyclo-polymerization of specially designed difunctional perfluoromonomers such as perfluoro(allyl vinyl ether) which is readily derived from the carboxylated perfluoro(vinyl ether). The novel perfluoropolymer with a cyclic structure in the main chain is characterized by an exceptional transparency, and has been commercialized with expectation of major applications in electronics industries.     

New findings on thermal degradation properties of fluoropolymers

In this paper, the thermal degradation properties of Viton A and Fluorel are investigated by both isoconversional and combined kinetic analysis methods using non-isothermal thermogravimetry technique. It has been found that the heating rate has little affect on the degradation residue of Fluorel and Viton A, where around 1.3% char was formed for Fluorel and 3.5% for Viton A. Different from the literature, the decomposition of Viton A should be considered as an overlapped dehydrofluorination and carbon chain scission process, with activation energy of 214 ± 11 and 268 ± 13 kJ mol^?1, respectively. The effect of dehydrofluorination on degradation of Fluorel is not so significant due to low content of H, and hence, it could be considered as a single-step mechanism with average activation energy of 264 ± 14 kJ mol^?1. The thermal stability of Fluorel is much better than that of Viton A, and the predicted half-life is around 218 min for Fluorel and 49 min for Viton A at 420 °C, which are consistent with experimental values. If using a single-step model as in the literature for Viton A, its half-life at 420 °C would be underestimated for >20%.     

Polymer composites based on polyvinyl chloride

Binary and ternary polymer blends based on polyvinyl chloride with ethylene–propylene–diene rubber were studied. A comparative analysis of the effect of a low-molecular-weight plasticizer and high-molecular-weight thermoplastic additives on the deformation and strength characteristics of the composites and on the viscosity of their melt was made. The compatibilizing ability of the plasticizing additives and the possibility of the replacement of the low-molecular-weight plasticizer by the polymeric component were evaluated.     

Functional composites based on polybenzimidazole and graphite nanoplates

A procedure was developed for preparing stable dispersions of graphite nanoplates with the concentration of up to 25 mg mL^–1 by two-step ultrasonic treatment of graphite in N-methyl-2-pyrrolidone. A series of elastic films based on poly-2,2′-p-oxydiphenylene-5,5′-bisdibenzimidazole oxide with the filler content of up to 45 wt % were prepared from such dispersions. Introduction of the nanoadditive into the matrix of the heterocyclic polymer results in 47% enhancement of the tensile strength of the materials and in an increase in the temperature of the 10% weight loss by 52–81°C. In addition, the films are characterized by high electrical conductivity reaching 480 S cm^–1 for the composite with 45 wt % graphite nanoplates and exhibit tensoresistive properties, which allows using them in various electrotechnical devices and fabric engineering structures.     

Biodegradable polymer composites based on polylactide and cellulose

Blends of polylactide with microcrystalline cellulose are obtained under high-temperature shear deformation. In order to improve plasticity and biodegradability of the system, low-molecular-mass poly(ethylene glycols) of various molecular masses are introduced into the composites. The mechanical and thermophysical properties of these composites, as well as their water and moisture absorptions, are studied. The morphology and biodegradability of the samples are investigated with the use of various physicochemical and biological methods.     

Polymeric composites based on alicyclic polyimide and polyaniline

Specific features of modification of an alicyclic polyimide with polyaniline were examined. The thus obtained new polymeric composites exhibit better capability for silver plating.     

Polymer composites based on polythiourethane and fluorinated organomontmorillonite

Russian Journal of Applied Chemistry - The effect exerted on the mechanical properties and thermal oxidative stability of polythiourethane elastomers by new organomineral complexes based on...     

Organoinorganic composites based on tetraethoxysilane and nitrogen polybases

Hybrid organoinorganic composites insoluble in water and organic solvents were prepared by the hydrolysis of tetraethoxysilane in the presence of poly-1-vinylpyrazole, poly-1-vinylimidazole, and poly-4-vinylpyridine. The composition of the composites was determined by the nature of the polymeric nitrogen base and hydrolysis conditions. The composites synthesized showed high sorption activity in the extraction of the [PdCl₄]^2?, [PtCl₆]^2?, and [AuCl₄]^? ions from hydrochloric acid solutions.     

Biopolymer composites based on modified lignin and nanocellulose

New composite lignocellulose materials were prepared using modified lignin and nanocellulose. The materials were studied by elemental and thermal gravimetric analysis, and their tensile tests were performed. The results obtained show that addition of nanocellulose to modified lignin makes possible its use as filler in paper production.     

Conductive composites based on chitosan and polyvinylpyrrolidone-stabilized graphene

Highly concentrated dispersions of polyvinylpyrrolidone-stabilized graphene were prepared. Using transmission electron microscopy, it was found that the graphene particles consisted, on average, of one to four layers, with the lateral size of 50–400 nm. From these dispersions, new film composites of chitosan with the filler content up to 4 wt % characteristic of electrical conductivity as high as 1.9 × 10^–2 S/cm were formed.     

New polymer composites based on keratin and polyethylene

New biodegradable composites based on keratin and polyethylene have been produced under shear deformation. It has been demonstrated that the introduction of keratin leads to an increase in elastic modulus and to a decrease in ultimate tensile strength and elongation at break of the compositions. Elongation at break ε_b depends on the keratin dispersity; the highest ε_b values are observed for the compositions containing the smallest keratin particles. It has been shown that the compositions are susceptible to mold fungi; i.e., they are biodegradable.     

Structure-property relationships for carbochain fluoropolymers

Polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF) and polychlorotrifluoroethylene (PCTFE) were studied by differential calorimetry at normal pressure in the temperature interval 130–555 K, and by pressure dilatometry in the temperature interval 303–545 K and in the pressure range 14–70 MPa. Pressure derivatives of the melting temperature,dT _m/dP, were used to calculate the true melting entropy S _m from the Clausius-Clapeyron equation, while equilibrium values of the melt specific volume were treated according to the Simha-Somcynsky cell theory. Comparison of the experimental data for PVF, PVDF and PCTFE with pertinent published data for polyethylene (PE) and polytetrafluoroethylene (PTFE) showed that a steady decrease of S _m and of the conformational contribution to S _m reflects the increase of the equilibrium chain stiffness as the hydrogen atoms of the hydrocarbon chain (PE) are substituted with bulkier fluorine and/or chlorine atoms (PCTFE, PTFE), while a concomitant drop of the pressure reducing parameter from the cell model and an increase of melt compressibility and the derivative,dT _m/dP, should be attributed to the increase of the free volume fraction of the melt in the series, PE to PTFE.     

Drop size dependence of contact angles on two fluoropolymers

Young’s equation predicts that the contact angle of a liquid drop is independent of its size. Nevertheless, large drop size dependences of contact angles have been observed, especially for millimetre-sized drops, on a variety of solid surfaces. We report new measurements of drop size dependence of contact angles for several liquids on two fluoropolymer surfaces, Teflon AF 1600 and EGC-1700. We demonstrate a new strategy for contact angle measurement that allows detection of approximately 0.1° changes in the contact angle during the growth of a drop. We find that on the surfaces examined, drop size dependence of contact angles is ten times smaller than on all previously studied fluoropolymers at the millimetre scale. The data are insensitive to various attempted surface modifications. We discuss the interpretation of the data and possible physical sources.     

Quantum chemistry studies of unbranched fluoropolymers

The results of quantum chemistry calculations of energy and topology parameters, vibration and NMR spectra of model fluorocarbon and unbranched hydrocarbon molecules are presented in this work. The formation of radicals and branches in fluorocarbon molecules and mechanisms of hydrogen substitution by fluorine at fluorination of hydrocarbon paraffins and polymers are discussed based on obtained results.     

离聚物及其共混体系的研究3.基于配位络合的增容作用

通过将苯乙烯(S)与少量的甲基丙烯酸(MAA)或马来酸酐(MA)共聚及甲基丙烯酸正丁酯(nBMA)与4-乙烯基吡啶(4-VP)共聚,从而在聚苯乙烯(PS)及聚甲基丙烯酸丁酯(PBMA)链上分别引入了功能基团羧酸基(-CO-OH)、酸酐基(-CO-O-CO-)和吡啶基(-N)。通过与锌盐作用获得相应的离聚物(Ionomer)。用红外光谱(IR)表征了共聚物和离聚物的形成;差热分析(DSC)测定共聚物、离聚物和共混物的玻璃化转变温度(Tg)。研究结果表明,随着共聚物中功能基团含量的增加或者共聚物形成离聚物后,其玻璃化转变温度(Tg)提高了;而共聚物的共混物因羧酸基与吡啶基间的质子转移作用而提高了相容性。特别是在引入Zn~(2+)的共混物中,增容作用十分明显,这可归结于BMAVP中的吡啶基和SMAA-Zn~(2+)(或SMA-Zn~(2+))中的Zn~(2+)间的配位络合作用的贡献。