Nano-Modeling Structure and Micromechanical Properties of Mesoscopic Composite Systems

Abstract

We discuss the results of molecular modeling (quantum mechanics and molecular dynamics methods) of mesoscopic composite systems based on thermoplastic (polyethylene, polypropylene, etc.) and elastomeric (polybutadiene, polyisoprene, etc.) polymer matrices and active nanofillers (commercial carbon in different structural modifications, silicate, fullerens, nanotubes). Consideration is given to the structure, energy and micromechanical properties of model particles of commercial carbon, including those with surfaces terminated with various chemical compounds, and to the adsorption of various polymer chains on them. Shear strain and uniaxial tension in different adsorption complexes as well as molecular friction are calculated. The reinforcement effect, i.e. the change of most important physico-mechanical characteristics, and energy parameters are analyzed. We make important inferences about the influence of filler properties on its activity during interaction with polymer matrix particles. It is noticed that the best adhesion of polymer chain fragments (largest force of microscopic molecular friction) is observed for the isoprene elastomer — silicate filler system. Such nanoparticles as fulleiene and carbon nanotubes exhibit weak (almost equal) molecular adhesion, which makes it impossible to consider them as promising reinforcing fillers without proper modification. Carbon fillers are found to exert a different effect on the structure of thermoplastics and elastomers. In the first case, the structure becomes amorphous, while in the second one it stabilizes. This explains the known effect of elastomer reinforcement with carbon fillers. Thus, we have developed molecular simulation algorithms and methods, which employ parallel computing technologies on a supercomputer, to study the structure and micromechanical characteristics of large molecular systems, namely, clusters of representative elements of polymer composites. Based on the investigation by quantum mechanics and molecular dynamics methods, conclusions have been made concerning the effect of the filler nature on its interaction with polymer molecules comprising the polymer composite matrix.