The Systems Polyamides-Carbon Nanofillers: Quantum-Chemical Modeling and Experimental Characteristics

It has been experimentally shown that thermomechanical processing of polyamides in an oxidizing environment (in air) leads to structural degradation and loss of mechanical characteristics of the polymer. Reinforcement of polyamides PA6, PA6.6, PA12 with a nanosized carbon filler (carbon nanotubes (CNTs) and graphene nanoparticles) in small quantities (up to 0.5%wt) ensures sufficient distribution and interaction of individual particles, not their agglomerates, with the polymer matrix. This increases the heat resistance of nanocomposites but does not completely compensate for the effect of degradation during thermomechanical processing, although it brings the characteristics of the composite closer to the initial state of the polymer. Reinforcement with CNTs significantly increases the mechanical characteristics, the work of destruction of the nanocomposite (by 3–4 times) compared to the unfilled polymer that underwent the same thermomechanical treatment. Addition of 0.25%wt. CNTs up to PA6, which is used as a binder in three-layer fiberglass, increases the tensile strength by almost two times. Quantum chemical calculations carried out using DFT method with the B3LYP exchange-correlation functional, the 6-31G(d,p) basis set and the Grimme dispersion correction showed that the calculated values of the intermolecular interaction energy in the polyamide nanocomposite cluster—graphene-like plane for all the studied models increases compared to similar values for two fragments of pure polyamide due to the strengthening of hydrogen bonds in the polymer matrix. Such an effect can led to an increase in thermal resistance and mechanical properties of nanocomposite. Therefore, the experimental data are qualitatively consistent with the results of quantum chemical calculations.