Vol 42, No 11 (2023)

Polymer-matrix composites based on ethylene vinyl acetate (EVA) and KxCoyTi8 – yO16 solid solution
with a hollandite-like structure (KCoTO(H)) are obtained and studied as promising materials for components
of electronic devices. The filler is synthesized by modifying X-ray amorphous potassium polytitanate
(PPT) K2O·nTiO2 (n = 4.3) in a CoSO4·7H2O solution under alkaline conditions, followed by thermal treatment
at 900°C. The structure of the synthesized material and the morphology of particles are studied by X-ray
phase analysis (XPA) and scanning electron microscopy (SEM), respectively. KCoTO(H) is introduced in the
EVA polymer matrix by mixing a preliminarily prepared polymer solution and a dispersion of filler powder in
an appropriate solvent in amounts of 10, 20, 30, 40, and 50 vol %. The frequency behavior of the permittivity,
dielectric loss tangent, and conductivity of the obtained composites is studied by impedance spectroscopy. It
is established that an increase in the KCoTO(H) content in the composite contributes to the growth of all the
studied dielectric characteristics of a relatively pure EVA polymer matrix in the entire frequency range of
0.1 kHz–1 MHz (the maximum values are noted at a 50 vol % of the filler and f = 102 Hz: ε = 518, tanδ = 4,
and σ = 1.35 S/cm).

Изучено становление сдвиговой адгезионной прочности систем эпоксиангидридная матрица – волокно при разных режимах отверждения. Показано, что становление прочности происходит в несколько этапов. Также исследовано изменение степени отверждения и температуры стеклования матрицы в процессе отверждения.

Polymer composites with nanoparticles localized on the surface of polytetrafluoroethylene microgranules
are synthesized by the method of thermal decomposition of metal-containing nickel salts. The synthesized
nanoparticles are characterized by transmission electron microscopy (TEM) and X-ray diffraction
analysis. The size of the nanoparticles ranged from 3.5 to 8 nm, depending on the precursor. It follows from
the data obtained that the particles have a complex composition. The study of magnetic properties shows that
the system of magnetic nickel-containing nanoparticles in the samples at room temperature is in a ferromagnetic
or superparamagnetic state. The blocking temperature and coercive force are calculated for each sample.

The results of a study of water absorption processes by samples of polymer composite materials
(PCMs) based on fiberglass, subjected to low-speed impact with controlled impact energy and alternating
temperature cycling are presented. Using magnetic resonance imaging (MRI), the distribution of absorbed
water in the fiberglass structure is visualized and the dynamics of its accumulation in various areas of the sample
are studied. It is found that mechanical impact leads to a nonuniform distribution of the absorbed water
in the samples and a significant accumulation of free water in the areas of destruction and adjacent layers in
the event of a violation of the integrity of the outer layer of the material. It is shown that cyclic alternating
temperature effects do not lead to a noticeable change in the water absorption processes and are comparable
in effect to mechanical nondestructive effects. The results obtained using MRI are in close agreement with
the data of traditional weight measurements, which shows the effectiveness of the method in diagnosing
defects and mechanical damage to PCMs exposed to the aquatic environment.

Filled nanocomposites of polylactide with graphite nanoplates (GNPs) and reduced graphene
oxide (RGO) are prepared by liquid-phase synthesis. A comparative study of the mechanical, electric, and
thermophysical characteristics of the compositions depending on the nature of the nanofillers is carried out.
An insignificant difference in the mechanical parameters of the compositions containing GNPs and RGO as
fillers is established. At the same time, when studying the electrical properties, it is found that the use of RGO
as a filler leads to the production of composites with a lower percolation threshold of the flow than in the case
of GNPs and increased conductivity. The differential scanning calorimetry (DSC) method shows that compositions
containing GNPs as a filler have a higher degree of crystallinity in comparison with similar compositions
containing RGO. This is caused by the structure of the filled compositions, which influences the
nucleation rate of polylactide (PLA) crystallites on the surface of ordered planar nanoparticles of the GNPs
and imperfect RGO particles. Thus, the use of different carbon nanofillers may promote the production of
compositions that differ in their characteristics.