Search

Polymer nanocomposites are widely used in various high-tech industries. Due to the combination of the elasticity of the matrix and the strength of the inorganic filler, they have improved functional characteristics compared to unfilled polymers. The article is devoted to determining the effect of carbon nanotubes (CNT) on the microstructure and properties of polymeric nanocomposite materials for 3D printing based on polycarbonate. As a result of this work, a series of composite materials was manufactured using a piston extruder. Their microstructure and functional characteristics were investigated using methods of optical microscopy, thermophysical, electrical and mechanical analysis. It was found that CNTs form clusters in the polymer matrix, which form a percolation network at a content of 0.5–0.8%. This feature of the structure formation of CNTs provided an abrupt increase in the functional characteristics of the materials obtained. It is shown that with an increase in the filler content in the system to 3%, the thermal conductivity rapidly increases to 1.22W/(m∙K). A similar effect is observed for the electrical conductivity, which increases by seven orders of magnitude from 10-12to 10-5S/cm at 3% CNT content in the system, exhibiting percolation behavior. With the introduction of CNTs, the crystallinity degree of the polymer matrix decreases by almost 15%, due to the fact that the developed surface of the nanotubes creates steric hindrances for polycarbonate macromolecules. This effect almost negates the reinforcing effect of nanotubes; therefore, the mechanical tensile strength with the introduction of 3% CNTs increases by only 21% compared to the unfilled matrix. In terms of their functional characteristics, the obtained materials are promising for the creation of filaments for 3D printing on their basis.

Polymeric materials that contain inorganic fillers demonstrate a unique set of physical properties due to the combination of matrix elasticity and filler strength. This paper reports determining the effect of dispersed aluminum particles on the properties of polyvinylidene fluoride-based materials. This study result is the fabrication of a series of composite materials using a piston extruder. Their functional characteristics have been explored using the methods of thermophysical and mechanical analysis, dilatometry, and acoustic spectroscopy. It was established that the introduction of dispersed aluminum particles leads to the loosening of the matrix, which may indicate the transition of macro macromolecules from the crystalline phase to the boundary layer around the filler. This feature of structure formation and the uniform distribution of filler particles ensured the improvement of the functional characteristics of the materials obtained. It has been shown that with an increase in the content of filler in the system to 5% the thermal conductivity increases from 0.17W/(m·K) to 1.55W/(m·K). The introduction of the filler leads to an improvement in the heat resistance of the materials obtained, by 17K. The increase in both melting point and destructiveness is explained by the formation of a more perfect polymer structure with a higher degree of crystallinity. An increase in the speed of ultrasound propagation was identified, by 67%, as well as in the tensile strength, by 36%, in the materials obtained, which can be explained by contributions from the filler, which has greater sound conductivity and mechanical strength than the polymer matrix. Such systems show the reinforcing effect of aluminum particles on the polymer matrix, so they could be used as structural materials with improved functional characteristics

The ionic association in nanocomposite polymer electrolytes based on polyether, lithium perchlorate and nanosized laponite was studied using the data of ionic conductivity and Fuoss-Kraus formalism. It was established that with increasing salt content, the conductivity of the electrolyte initially increases, reaching a maximum at 1-1.3 mol/kg with a subsequent decrease, which is associated with ionic association. It is found that increasing the temperature and the introduction of the filler increases the number of free ions, which leads to an increase in conductivity. The introduction of nanoclay into the polymer electrolytes leads to an increase in their electrical conductivity. This method of modification is can be used for the development of polymer electrolytes with improved functional characteristics for lithium current sources.

The structure features and intercalation processes in oligoethylene glycol (OEG)-based systems and organoclay were studied using X-ray diffraction analysis. It is established that after the introduction of surfactants, the interlayer distance in montmorillonite (MMT) increased. This indicates the intercalation process of surfactant molecules into the interlayer space of the MMT. After introduction to polymer matrix the increase in the interlayer distance is observed. This indicates the intercalation of two monolayers of OEG and the formation of quasibilayer structures. It is shown that the structure of OEG-based systems significantly depends on the content of the nanofiller. Partial processes of intercalation are observed in OEG-organoclay nanocomposites.

The research of features of electrical conductivity of polyurethane nanocomposite materials, filled with multiwalled carbon nanotubes depending on pressure is done using the impedance spectroscopy method. The conductivity dependences of the systems based on polyurethane and multiwalled carbon nanotubes from the applied external pressure are received, and these dependences are also modelled in the frame of the scaling approach and the percolating theory. It is shown that the probed systems are perspective and can be used as piezoresistive materials for sensors of pressure. It was shown, that sensor, which contains 3 % nanotubes, demonstrates the greatest speed of reacting and sensitiveness.

In this work, we used impedance spectroscopy to study the electrical conductivity of the systems based on polyethylene oxide and multiwalled carbon nanotubes at different temperatures. The concentration dependence of the electrical conductivity exhibits percolation behavior. Its value increases more than 40 times in the temperature range from 273 K to 343 K. We propose that the studied systems are perspective thermoresistive materials for temperature sensor applications.

A modified theoretical model of the electrical conductivity of polymer nanocomposites is proposed, which describes the experimental results for polyether-carbon nanotubes (CNTs). This model takes into account the contributions to the total electrical conductivity from the polymer matrix, interfacial layers at the polymer-CNTs interface, and direct contacts between CNTs. It describes the experiment in a wide range of CNTs concentrations and allows to obtain comprehensive information about the processes of charge transfer in the system.

The relaxation processes in nanocomposite polymer electrolytes based on polyethylene glycol was studied using the method of dielectric relaxation spectroscopy. The relaxation times and the activation energy was calculated using the Arrenius equation. The extreme behavior of relaxation parameters at the maximal nanofiller content in polymer electrolytes was observed.

The frequency dependences of the electrical and dielectric characteristics of systems based on polyethers and carbon nanotubes (CNTs) are modelled, using the theoretical models. The frequency dependences of electrical and dielectric characteristics in the field of percolation transition can be described within the framework of percolation theory using universal scaling laws. The results of the frequency dependence modelling of electrical and dielectric characteristics are analysed in the framework of the intercluster polarization model and the anomalous diffusion model. The model of intercluster polarization is better suited to describe the percolation behavior of polyether _ CNT systems.

We investigated the features of conductivity of polymer electrolytes based on polyethylene glycol, LiClO 4 and organomodified laponite using the method of impedance spectroscopy. It is shown that the electrical conductivity of PEG-based systems is significantly dependent on the salt content. It is found that the conductivity has an extreme dependence on the LiClO 4 content. At a salt concentration of Li/O = 1/4, the conductivity of the system is independent of temperature, indicating the formation of ionic aggregates. The introduction of laponite nanoparticles (1%) into the polymer electrolyte leads to an increase in electrical conductivity by reducing the crystallinity and destruction of ionic aggregates. Further increase in the content of the filler reduces the electrical conductivity.

The effect of carbon black (CB) nanopowder on the electrical properties of polymer composite systems based on the epoxy resin is investigated using the method of impedance spectroscopy. It is established that the electrical and dielectric properties of the studied systems significantly depend on the nanofiller content. It is found that electrical conductivity and dielectric constant exhibit percolation behavior when the filler’s content increases. In this case, the electrical conductivity increases exponentially, indicating the formation of filler electrically conductive mesh inside the polymer matrix. A small jump in electrical conductivity when reaching the percolation threshold indicates the formation of indirect contacts between the particles. The value of the percolation threshold of conductivity is 8%. It is shown that the dielectric constant of epoxy nanosystems is almost unchanged in the frequency range of 102–105 Hz. It is related to the structural features of the filler particles, which ensure the existence of a minimal dielectric gradient between the matrix and the filler. It is found that the dielectric constant of the studied systems also shows percolation behavior. The obtained material based on the epoxy matrix is characterized by a high value of dielectric constant, which at a carbon black nanopowder content of 29% is 4680. This material is characterized by relative frequency invariance and a high value of dielectric constant, so it has great potential for practical application.