Mechanical Performance of Polystyrene-Based Nanocomposites Filled with Carbon Allotropes

Numerous studies have been performed on different aspects of the mechanical behavior of polymer nanocomposites; however, the results obtained still lack a comprehensive comparative analysis of the mechanical properties of composites containing nanofillers of different shapes and concentrations and subjected to different static and dynamic loads. Carbon nanofillers were shown to provide the most significant improvement in the elastic properties of polymer composites. In this paper, we present a comparative analysis of the mechanical properties of polystyrene-based nanocomposites filled with carbon allotropes of different shapes: spherical fullerene particles, filamentary multi-walled nanotubes, and graphene platelets, fabricated by the same technology. The influence of shape and concentration of dispersed carbon fillers on mechanical and viscoelastic properties of composites in different stress–strain states was evaluated based on the results of tensile and three-point bending tests, and ultrasonic and dynamic mechanical analysis. Comparison of the static and dynamic elastic properties of nanocomposites allowed us to analyze their variations with frequency. At low concentrations of 0.1 wt% and 0.5 wt% all nanofillers did not provide significant improvement of elastic characteristics of composites. More efficient reinforcement was observed at the concentration of 5 wt%. Among the filler types, some increase in composite rigidity was observed with the addition of filamentary particles. The introduction of the layered filler provided the most pronounced rise in the composite rigidity. The weak frequency dependence of the mechanical loss tangent, which is characteristic of amorphous thermoplastics, was demonstrated for all the samples.