Small-angle neutron scattering, dielectric spectroscopy, and dynamic mechanical analysis data are reported for composites of isotactic polypropylene (IPP) with graphene nanoparticles (GNP) and nanographite. In various samples, the volume of the IPP matrix with a high degree of crystallinity contains GNP with concentrations of 0.7 and 1.8 wt

The results of a comprehensive investigation into the structure and properties of nanodiamond soot (NDS), obtained from the detonation of various explosive precursors (trinitrotoluene, a trinitrotoluene/hexogen mixture, and tetryl), are presented. The colloidal behavior of the NDS particles in different liquid media was studied. The results of the scanning electron microscopy, dynamic light scattering, zeta potential measurements, and laser diffraction analysis suggested a similarity in the morphology of the NDS particle aggregates and agglomerates. The phase composition of the NDS nanoparticles was studied using X-ray diffraction, Raman spectroscopy, electron diffraction, transmission electron microscopy, atomic force microscopy, and scanning tunneling microscopy. The NDS particles were found to comprise both diamond and graphite phases. The ratio of diamond to graphite phase content varied depending on the NDS explosive precursor, while the graphite phase content had a significant impact on the electrical conductivity of NDS. The study of the mechanical and tribological characteristics of polymer nanocomposites, modified with the selected NDS particles, indicated that NDS of various types can serve as a viable set of model nanofillers.

Aspects of solid-state processing of nascent disentangled ultra-high-molecular-weight polyethylene (UHMWPE) powders of different syntheses mixed with electrically conductive carbon nanoparticles (NPs) of various types are studied. Effect of multiple parameters of the processing procedures on the electrophysical characteristics of the composite samples is investigated. Such parameters include time of preliminary ultrasonication (US) of NPs, time of US of UHMWPE/NPs mixtures, molding time, temperature, and pressure, deformation degree, etc. It is observed that by selecting optimal values of such parameters it is possible to obtain samples of composites with an extremely segregated structure made of the NPs, with NPs distributed evenly on the surfaces of the compacted UHMWPE powder particles. This ensures high levels of conductivity at very low values of NPs content. The segregated structure is retained when the composites are strengthened using the solid-state uniaxial shear deformation process. While conductivity of most of the composites filled with various types of NPs monotonously decreases with the deformation ratio, conductivity of the composites filled with exceptionally long double-walled carbon nanotubes is maintained. The processed oriented composites are also characterized by high EMR shielding properties, as well as interesting temperature dependencies of the electrical conductivity.

Basing on the data of small-angle neutron scattering for the nanocomposite composed of fullerene C60 (16.5 wt. %) in the matrix of isotactic polypropylene, we received information on clusterization of nanoparticles and defined their geometric parameters and dimensionality. In this paper, we propose interpretation of particle aggregation possessing the properties of surface fractal in the size range up to 80 nm observed using small-angle neutron scattering method. Basing on the well-known theories of defect structures of a fullerene molecule C60 in non-Euclidean metrics, in particular, of disclinations and monopole in two-dimensional spherical Gödel space—time, we formulate a lattice version for the action of monopole gas, in which with the lattice Monte Carlo method, using abelian projection, we estimate the energy of monopole currents at different monopole concentrations. In frames of the proposed model, it is possible to calculate fractal properties of the fullerene C60 in a polymer composite and also to interpret evolution of disclinations.

The stages of solid-state processing of nanocomposites, based on nascent disentangled ultra-high-molecular-weight polyethylene (d-UHMWPE) reactor powders (RPs) and carbon nanoparticles (NPs) of various types, were meticulously investigated. The potential for optimizing the filler distribution through variation of the processing parameters, and the impact of the d-UHMWPE RP and nanofiller type on the electrical conductivity of the resulting composites were discussed. The specifics of the dependences of conductivity and tensile strength on the deformation ratio for the composites, oriented under homogeneous shear conditions, were investigated. The obtained results and the results on piezoresistivity and temperature dependency of conductivity in the oriented and compacted composites demonstrated the independence of the UHMWPE matrix orientational strengthening on the filling. The interchangeability of high-temperature uniaxial deformation and deformation under homogeneous conditions for orientational strengthening and electrical conductivity changes in the preliminary oriented composite samples was confirmed. The potential for simultaneously achieving high strength and conductivity in composite tapes and the possibility of directly processing d-UHMWPE RP and NPs mixtures into oriented composite tapes were demonstrated. The overall results suggest that the studied composites may serve as a viable model system for investigating the deformational behavior of conductive networks comprising NPs of varying types and contents.

Based on small angle neutron-scattering data from a nanocomposite composed of fullerene C60 (16.5 wt

Structural studies were carried out and physicomechanical characteristics of samples of ultrahigh molecular weight polyethylene (UHMWPE) were determined for successive stages (compacting/monolithization—orientational stretching) of the continuous solid-state processing of nascent reactor powders of UHMWPE (RP UHMWPE) into high-strength tapes. The use of nascent RP UHMWPE with the morphology, molecular weight, and bulk density optimal for solid-state processing makes it possible to obtain high-strength (∼3 GPa) and high-modulus (120–130 GPa) tapes. The conditions for both compacting/monolithization and the orientational stretching have a significant effect on the structure and properties of highly oriented tapes and can be optimized in order to prepare materials with a complex of the highest elastic-strength characteristics.

In this work, a multi-scale and multi-physics model taking into account structure-property relationships that are interconnected across the length scales is developed to predict electrical conductance deformational behavior for glass fiber reinforced electroconductive nanocomposites (GFRNCs). To verify numerical model predictions, composites with polypropylene (PP) matrix filled with nanoparticles and reinforced with woven glass fibers were manufactured. As nanosized electroconductive fillers multi-walled carbon nanotubes and carbon black particles were used. Uniaxial deformation of the obtained GFRNCs with simultaneous continuous electrical conductance measurements was performed. Results of the numerical modeling were compared with experimental data obtained for modified PP and for GFRNCs. It was concluded that introduction of woven glass fiber in the electrically conductive matrix noticeably affects electrical conductivity changes with deformation for the material, which can be adequately predicted numerically using proposed multi-scale modeling approach for correct composite structure representation.

The highly conductive composite based on graphite nanobelts/ultra-high-molecular-weight polyethylene (UHMWPE) was developed using hot calendering at temperatures below the polymer melting point. The fabricated material exhibits excellent electrical conductivity (up to 40 S cm−1), high efficiency of electromagnetic interference shielding (near 35 dB for 100 μm thick samples) and good mechanical properties (flexibility and mechanical strength). These superior characteristics are the result of synergistic combination involving superior mechanical properties of the polymer, perfect transport characteristics of the filler and the specific method of fabrication allowing for formation of a segregated anisotropic conductive network with a low percolation threshold (0.42 vol %).

A correlation was established between, on the one hand, the values of the molecular weight of UHMWPE synthesized using postmetallocene bis-phenoxyimine catalysts and the bulk density of synthesized nascent reactor powders of UHMWPE, and, on the other hand, the values of the elastic modulus, breaking strength and breaking elongation of oriented tapes obtained from reactor powders of UHMWPE by the method of solid-state processing below the melting temperature of the polymer without the use of solvents. It has been established that the application of UHMWPE reactor powders with a bulk density of no higher than 0.09 g/cm3 and, at the same time, a polymer molecular weight of not less than 4.5 × 106 g/mol allows one to obtain on their basis by a solid-state method, simultaneously, high-strength (breaking strength up to 3.6 GPa) and high-modulus (modulus of elasticity up to 150 GPa) materials, that is, having the maximum value of the deformation energy to break, which is important for practical applications. Reactor powders of UHMWPE with optimal for solid-state processing values of MM and bulk density, at the level of structural subunits of the nanometer size range had a morphology of the “stack of lamellas” type.

A phenomenon of change in the frequency of a mechanically activated current was detected for the first time. This phenomenon consists in the fact that electric current pulses produced by a rheological explosion differ in frequency characteristics between a polypropylene‑graphene nanoplates composite and the matrix polymer (polypropylene). It was shown that the Fourier transforms of the current signals from the composite according to the Havriliak–Negami model for the experimental frequency dependence of conductivity agree well with the results of the calculation using the Drude model for multilayer graphene.

In this work, the results of a complex investigation of structure and properties of nanodiamond soot (NDS) of detonation synthesis are presented. Size distribution of NDS particles, dispersed in different liquid media, was investigated using dynamic light scattering and laser diffraction analysis methods. The results of the investigation, as well as the results of zeta-potential measurements, allowed us to characterize the agglomeration process of the NDS particles as independent of the medium, making NDS a good model filler for research of composite-modified nanosized particles. Additional data obtained using scanning electron microscopy, scanning tunneling microscopy, atomic force microscopy, X-ray diffraction, and Raman spectroscopy, demonstrated that in NDS the spherical nanodiamond (ND) particles with diameter ~5 nm are densely packed into strong-coupled aggregates with diameter ~300 nm, surrounded by graphite nanoribbons. X-ray diffraction analysis estimated the volume fraction of NDs in NDS as ~45 vol.%, simultaneously showing that the graphite is not defective, which was confirmed with the electron diffraction method. It was demonstrated that this structure of NDS allows to efficiently use NDS as a filler for polymer composites to increase polymer characteristics such as electrical conductivity or tribological characteristics, similarly to conventionally applied fillers such as carbon black.

Conducting polymers have wide technological applications in sensors, actuators, electric and optical devices, solar cells etc. To improve their operational performance, mechanical, thermal, electrical and optical properties, such polymers are doped with carbon allotrope nanofillers. Functionality of the novel nanocomposite polymers may be stipulated by size characteristics of nanoparticles and the polymer, different physical effects like charge transfer in such objects etc. We characterize and analyze structure, elastic, electric properties and of novel polymer nanocomposites, isotactic polypropylene (iPP) with high crystallinity, doped with graphene nanoplates (GNP) and nanographite particles at different concentrations and sizes about 100 nm, basing on the results of dynamic mechanical analysis (DMA), dielectric spectroscopy, small-angle neutron scattering (SANS) and theoretical modeling. Carbon NPs aggregated in fractal objects in the bulk of iPP change its mechanical plastic, elastic and electric properties comparing with pristine polymer. We study modification of nanofiller morphology with the concept of Cosserat elasticity which involves description of the behavior of linear topological defects caused aggregation of nanographite and GNPs. We supply our experimental data with numerical simulations on the lattice in frames of the model of Cosserat elasticity to estimate some mechanical characteristics of the whole composite iPP.

Process of nanoscale carbon filler migration in polymer composite melts is studied. Monotonous decrease of electrical resistance is observed for composite materials during their stay in a melted state. This is especially pronounced for composites with concentration of filler much lower than percolation threshold determined for a specific matrix/filler/mixing method combination. This phenomenon can be observed for composites based on different polymer matrices. Also, it is demonstrated that the type and geometry of the electrically conductive filler does not affect presence of the phenomena. A setup for measurement of conductance for volume and surface layer components is used. The results of electrical conductance measurements of the polymer composite melt using this setup allows to attribute the increase of composite material conductance to formation of filler enriched surface layer. To obtain information on the processes occurring at the microscopic level, molecular dynamics simulations are conducted. Variation of several simulation parameters with comparison of the results to experimental data allows to understand the macroscopic composite material conductance behavior.

Data on the morphology of carbon allotrope nanoparticles in an isotactic polypropylene (IPP) matrix are analyzed. They are obtained using the small-angle neutron scattering method and a YuMO spectrometer at the IBR2 reactor of the Frank Laboratory for Neutron Physics, Joint Institute for Nuclear Physics (Dubna, Russian Federation). The fractal dimensionality is calculated, the form is reconstructed, and the geometric dimensions of the obtained particles and aggregates of single-wall carbon nanotubes (SWCNTs) in the IPP volume taken in concentrations of 1.2, 2.6, and 8 wt % are determined using ATSAS software. It is established that nanotubes form fractal nanoobjects with a rough surface in the IPP volume. Composite IPP/SWCNT systems are polydisperse to a significant degree; nanotubes twist into coils and knots and become more densely packed; in the polymer volume, the dimensions of the formed nanoparticles and their aggregates are several times larger than the initial ones used during synthesis. A model of knot formation in polymer materials based on calculating the asymptotic Hopf invariant and the lattice fractal dimensionality is used in this paper to interpret the results and predictions of the possible morphology forming in samples of such a type. The energies and probabilities of knot formation are estimated qualitatively using the Monte Carlo method.

Appearance of the rheological explosion in PE pellets with different molecular weights is investigated. The duration of the first and second stages of the rheological explosion is almost independent of MW. The moment of irreversible destruction of the sample and the value of rheological explosion threshold linearly decrease with an increase in the length of the polymer chain. As a result of the explosion, the heat of melting of polymers with MW values equal to 3 × 105 and 1 × 106 decreases, while for PE with M = 3.5 × 104 the heat of melting remains almost unchanged. Electric current pulses are recorded. Their Fourier images are in the form of band spectra described by the Lorentz models for a damped harmonic oscillator and the Havriliak–Negami model for dielectric relaxation. Experimental data suggest that the rheological explosion is associated with the accumulation of elastic energy in the amorphous phase of PE and, during the rheological explosion, polymer chains are broken to generate radicals •RO2.

We study the aggregation of carbon allotrope nanofillers in the matrix of isotactic polypropylene with direct small-angle neutron scattering measurements. With the ATSAS software, we analyzed the data and determined the fractal shape, dimension, and sizes of nanofiller aggregation in the bulk of isotactic polypropylene over the range of the scattering angles. We estimated the volume distributions and aggregation of different types of carbon nanofillers at different concentrations: nanographite, graphene nanoplatelets (GNP), fullerenes, single-walled carbon nanotubes (SWCNT), multi-walled carbon nanotubes (MWCNT) and binary fillers MWCNT/GNP. We reconstructed the shape of nanoscale particles and aggregates of a few nanofillers SWCNT, MWCNT and MWCNT/GNP and found that the systems are polydisperse; nanofillers associate in the volume of isotactic polypropylene as fractal dense aggregates with rugged surface, their sizes exceeding original dimensions of nanofillers several times.

In this work, the results of investigation of the effect of polymer composite melts electrical conductance increase with time are presented. The conductance time dependencies were obtained for composites based on polypropylene filled with carbon nanoparticles of different types. The dependencies were analyzed to demonstrate the possibility of correlation of the conductance kinetics with different composite parameters, such as the filler geometry. Additional studies were carried out, such as electron microscopy study, conductance measurements after consecutive surface layer removal, and composite melt conductance measurements using a three-electrode scheme. The results showed that the increased electrical conductance of the composite materials can be attributed to the formation of an enriched with the filler particles surface layer, which happens during the stay of the composite in a melt state. Analysis of the experimental data, along with the results of numerical modeling, allowed to suggest a possible filler distribution transformation scheme. The physical premises behind the investigated effect are discussed.