Modeling annular structures of carbon nanotubes as macromolecular coils - a possibility of gel formation

Carbon nanotubes (nanofibers) form folded ring-like structures in the polymer nanocomposite that look like macromolecular tangles. This behavior of these nanofillers is due to their high degree of anisotropy and low transverse stiffness. In this case, the ring-like structures of the nanotubes are considered as a macromolecular tangle, and the polymer matrix is considered as a solvent. This interpretation of nanocomposites polymer/carbon nanotubes makes it necessary to study the possibility of implementing the gelation process in them, which is understood as the transition of liquid (easily mobile and viscous) microheterogenic or homogeneous systems to the solid-phase state of gel or jelly. Gel formation is caused by the appearance of a spatial phase or molecular grid (frame) in the volume of the liquid system, which deprives the system of fluidity and gives it some properties of a solid body (elasticity, plasticity, brittleness, strength), which is of particular interest in studying the properties of polymer nanocomposites. The purpose of this work is to study the properties of polymer/carbon nanotubes (nanofibers) nanocomposites in the framework of the percolation theory and the possibility of implementing the gelation process in them. The possibility of gel formation by carbon nanotubes (nanofilaments), which are simulated as macromolecular coils, in nanocomposites based on polypropylene, is studied within the framework of the fractal analysis and the percolation theory. The paper shows that for achieving the point of gel formation the specific (straight-line) configuration of the indicated nanofillers is necessary and realization of this effect can lead to a sharp discrete change of nanocomposites in consideration. The authors find out that the effective elastic modulus of nanofillers in the polymer matrix is defined not by their stiffness, but by the efficiency of transfer of the applied mechanical stress from the polymer matrix to the nanofiller.