IMPLEMENTATION OF PUBLIC-PRIVATE PARTNER-SHIP PROJECTS IN THE RUSSIAN ARCTIC

The application of public-private partnership to stimulate the socio-economic development of the Arctic zone are considered. The importance of this task is determined by the fact that the reserves of natural resources located in the Arctic should provide the basis for the energy and economic security of the country. The comparative analysis of ways of realization of infrastructure projects on the basis of the state order and public - private partnership is carried out. The aspects of the influence of public-private partnership on the development of the region and increase its investment potential are discussed

Homogeneous Liquid Phase Transfer of Graphene Oxide into Epoxy Resins

© 2017 American Chemical Society.The quality of polymer composite materials depends on the distribution of the filler in the polymer matrix. Due to the presence of the oxygen functional groups, graphene oxide (GO) has a strong affinity to epoxy resins, providing potential opportunity for the uniform distribution of GO sheets in the matrix. Another advantage of GO over its nonoxidized counterpart is its ability to exfoliate to single-atomic-layer sheets in water and in some organic solvents. However, these advantages of GO have not yet been fully realized due to the lack of the methods efficiently introducing GO into the epoxy resin. Here we develop a novel homogeneous liquid phase transfer method that affords uniform distribution, and fully exfoliated condition of GO in the polymer matrix. The most pronounced alteration of properties of the cured composites is registered at the 0.10%-0.15% GO content. Addition of as little as 0.10% GO leads to the increase of the Young's modulus by 48%. Moreover, we demonstrate successful introduction of GO into the epoxy matrix containing an active diluent-modifier; this opens new venues for fabrication of improved GO-epoxy-modifier composites with a broad range of predesigned properties. The experiments done on reproducing the two literature methods, using alternative GO introduction techniques, lead to either decrease or insignificant increase of the Young's modulus of the resulting GO-epoxy composites

Intrinsic Insertion Limits of Graphene Oxide into Epoxy Resin and the Dielectric Behavior of Composites Comprising Truly 2D Structures

© 2019 American Chemical Society. The composites of graphene oxide (GO) with epoxy resin were prepared via the homogeneous liquid phase transfer method, allowing uniform distribution and nearly fully exfoliated condition of GO in the matrix. The ∼0.6% GO content is the absolute maximum that can be inserted into the epoxy matrix (at the flakes' size 5-20 μm) without sacrificing the exfoliation level of the 2D filler and the uniformity of the composition. Curing at 180 °C causes the in situ disproportionation, or so-called "thermal reduction" of GO in the matrix. The as-induced conductivity of GO flakes alters dielectric properties of composites via the Maxwell-Wagner polarization. For the first time, we experimentally demonstrate the dielectric properties of composite materials comprising truly 2D single-atomic-layer structures. They exhibit relatively low permittivity values that reach saturation at ∼0.2% filling fraction, and classical relaxation peaks on the imaginary part function at 0.3-0.4% GO content. The presented experimental data strongly suggest that the Maxwell-Wagner polarization is sufficiently suppressed in composites comprising truly 2D structures because of their interaction with the matrix. On the contrary, high permittivity values, reported simultaneously with the high loading fractions (>0.6% at the flakes' size 5-20 μm), are indicative of the nonsingle-layer character and/or the aggregation of the 2D inclusion particles in the polymer matrix

Intrinsic Insertion Limits of Graphene Oxide into Epoxy Resin and the Dielectric Behavior of Composites Comprising Truly 2D Structures

© 2019 American Chemical Society. The composites of graphene oxide (GO) with epoxy resin were prepared via the homogeneous liquid phase transfer method, allowing uniform distribution and nearly fully exfoliated condition of GO in the matrix. The ∼0.6% GO content is the absolute maximum that can be inserted into the epoxy matrix (at the flakes' size 5-20 μm) without sacrificing the exfoliation level of the 2D filler and the uniformity of the composition. Curing at 180 °C causes the in situ disproportionation, or so-called "thermal reduction" of GO in the matrix. The as-induced conductivity of GO flakes alters dielectric properties of composites via the Maxwell-Wagner polarization. For the first time, we experimentally demonstrate the dielectric properties of composite materials comprising truly 2D single-atomic-layer structures. They exhibit relatively low permittivity values that reach saturation at ∼0.2% filling fraction, and classical relaxation peaks on the imaginary part function at 0.3-0.4% GO content. The presented experimental data strongly suggest that the Maxwell-Wagner polarization is sufficiently suppressed in composites comprising truly 2D structures because of their interaction with the matrix. On the contrary, high permittivity values, reported simultaneously with the high loading fractions (>0.6% at the flakes' size 5-20 μm), are indicative of the nonsingle-layer character and/or the aggregation of the 2D inclusion particles in the polymer matrix

Fully exfoliated graphene oxide accelerates epoxy resin curing, and results in dramatic improvement of the polymer mechanical properties

© 2019 In this study, we propose a new approach for the homogeneous liquid-phase transfer of graphene oxide (GO) into epoxy resin. This makes the process more efficient, while achieving fully uniform distribution of GO flakes within the epoxy matrix. Introduction of as little as 0.4% and 0.6% GO drastically increases the viscosity of the compositions, pointing at the highly exfoliated condition of GO in the resin. A significant accelerating effect of GO on the curing reaction is attributed to reactive groups on the GO surface. The study of the thermo-mechanical properties revealed that the introduction of relatively small amount of GO (0.2 wt%) into the epoxy matrix results in the increase of the storage modulus by 25.4% (3035 MPa) relative to the neat epoxy polymer (2420 MPa). The use of the high-temperature curing agent affords the composites with significantly higher glass transition temperatures, compared to the low-temperature curing agent, broadening the scope of their potential applications

Polymer Composites Comprising Single-Atomic-Layer Graphenic Conductive Inclusions and Their Unusual Dielectric Properties

© 2020 American Chemical Society. In this study, we report the properties of the epoxy polymer composites, comprising reduced graphene oxide (RGO) in the form of the single-atomic-layer sheets. This structure is different from composites comprising multilayer RGO flakes and RGO aggregates, typically described in the literature. Viscosity of the uncured liquid resin increases by 390% after introducing 0.4% GO and increases by 4700% after its subsequent in situ reduction. The latter is explained by the reorganization of the original liquid crystalline structure of the GO-epoxy formulations with GO reduction. At the filling fractions >0.1%, the single-atomic-layer RGO flakes are assembled into clusters, where they alternate with a thin resin layer. This structure is also responsible for very unusual dielectric behavior of the cured solid composites. From one side, the real part of the complex permittivity reaches relatively high values at extremely low filling fractions: 14 at 0.1% and 60 at 0.4% RGO content. At the same time, the permittivity dispersion is accompanied with the well-pronounced symmetrical loss peaks on the imaginary part functions, which is typical for low permittivity materials. Such dielectric behavior is difficult to interpret in the frames of any single existing model. The high permittivity values strongly evidence for the Maxwell-Wagner interfacial polarization, even though the shape of the loss peaks would be better interpreted by α- and/or β-relaxation in neat solid polymers. The single-atomic-layer character of RGO affords a high interfacial area, which, in turn, translates to high capacitance and high permittivity. The relaxation time and activation energy, calculated from the temperature dependence experiments, suggest that the RGO clusters, but not individual RGO flakes, serve as conductive inclusions. The extremely long relaxation times are due to the charge transfer between the individual RGO flakes within the clusters. The striking difference between the newly prepared composites and control samples comprising multilayer RGO particles exemplifies the unique structure of our materials

Fully exfoliated graphene oxide accelerates epoxy resin curing, and results in dramatic improvement of the polymer mechanical properties

© 2019 In this study, we propose a new approach for the homogeneous liquid-phase transfer of graphene oxide (GO) into epoxy resin. This makes the process more efficient, while achieving fully uniform distribution of GO flakes within the epoxy matrix. Introduction of as little as 0.4% and 0.6% GO drastically increases the viscosity of the compositions, pointing at the highly exfoliated condition of GO in the resin. A significant accelerating effect of GO on the curing reaction is attributed to reactive groups on the GO surface. The study of the thermo-mechanical properties revealed that the introduction of relatively small amount of GO (0.2 wt%) into the epoxy matrix results in the increase of the storage modulus by 25.4% (3035 MPa) relative to the neat epoxy polymer (2420 MPa). The use of the high-temperature curing agent affords the composites with significantly higher glass transition temperatures, compared to the low-temperature curing agent, broadening the scope of their potential applications

Homogeneous Liquid Phase Transfer of Graphene Oxide into Epoxy Resins

© 2017 American Chemical Society.The quality of polymer composite materials depends on the distribution of the filler in the polymer matrix. Due to the presence of the oxygen functional groups, graphene oxide (GO) has a strong affinity to epoxy resins, providing potential opportunity for the uniform distribution of GO sheets in the matrix. Another advantage of GO over its nonoxidized counterpart is its ability to exfoliate to single-atomic-layer sheets in water and in some organic solvents. However, these advantages of GO have not yet been fully realized due to the lack of the methods efficiently introducing GO into the epoxy resin. Here we develop a novel homogeneous liquid phase transfer method that affords uniform distribution, and fully exfoliated condition of GO in the polymer matrix. The most pronounced alteration of properties of the cured composites is registered at the 0.10%-0.15% GO content. Addition of as little as 0.10% GO leads to the increase of the Young's modulus by 48%. Moreover, we demonstrate successful introduction of GO into the epoxy matrix containing an active diluent-modifier; this opens new venues for fabrication of improved GO-epoxy-modifier composites with a broad range of predesigned properties. The experiments done on reproducing the two literature methods, using alternative GO introduction techniques, lead to either decrease or insignificant increase of the Young's modulus of the resulting GO-epoxy composites

Homogeneous Liquid Phase Transfer of Graphene Oxide into Epoxy Resins

© 2017 American Chemical Society.The quality of polymer composite materials depends on the distribution of the filler in the polymer matrix. Due to the presence of the oxygen functional groups, graphene oxide (GO) has a strong affinity to epoxy resins, providing potential opportunity for the uniform distribution of GO sheets in the matrix. Another advantage of GO over its nonoxidized counterpart is its ability to exfoliate to single-atomic-layer sheets in water and in some organic solvents. However, these advantages of GO have not yet been fully realized due to the lack of the methods efficiently introducing GO into the epoxy resin. Here we develop a novel homogeneous liquid phase transfer method that affords uniform distribution, and fully exfoliated condition of GO in the polymer matrix. The most pronounced alteration of properties of the cured composites is registered at the 0.10%-0.15% GO content. Addition of as little as 0.10% GO leads to the increase of the Young's modulus by 48%. Moreover, we demonstrate successful introduction of GO into the epoxy matrix containing an active diluent-modifier; this opens new venues for fabrication of improved GO-epoxy-modifier composites with a broad range of predesigned properties. The experiments done on reproducing the two literature methods, using alternative GO introduction techniques, lead to either decrease or insignificant increase of the Young's modulus of the resulting GO-epoxy composites

Homogeneous Liquid Phase Transfer of Graphene Oxide into Epoxy Resins

© 2017 American Chemical Society.The quality of polymer composite materials depends on the distribution of the filler in the polymer matrix. Due to the presence of the oxygen functional groups, graphene oxide (GO) has a strong affinity to epoxy resins, providing potential opportunity for the uniform distribution of GO sheets in the matrix. Another advantage of GO over its nonoxidized counterpart is its ability to exfoliate to single-atomic-layer sheets in water and in some organic solvents. However, these advantages of GO have not yet been fully realized due to the lack of the methods efficiently introducing GO into the epoxy resin. Here we develop a novel homogeneous liquid phase transfer method that affords uniform distribution, and fully exfoliated condition of GO in the polymer matrix. The most pronounced alteration of properties of the cured composites is registered at the 0.10%-0.15% GO content. Addition of as little as 0.10% GO leads to the increase of the Young's modulus by 48%. Moreover, we demonstrate successful introduction of GO into the epoxy matrix containing an active diluent-modifier; this opens new venues for fabrication of improved GO-epoxy-modifier composites with a broad range of predesigned properties. The experiments done on reproducing the two literature methods, using alternative GO introduction techniques, lead to either decrease or insignificant increase of the Young's modulus of the resulting GO-epoxy composites