Polymer based nanocomposites: Effect of filler-filler and filler-matrix interactions

Nanocomposite materials present specific features, mainly due to their very high interfacial area, and a very short distance between reinforcing parti cles surface. For polymer based nanocomposites, reinforcing particles are m ost of the time much stiffer than the matrix. In that case, the percolation of those particles which occurs at a threshold fraction which depends on t heir shape factor (and on their dispersion characteristics) is shown to pla y a drastic role, especially if they form a rigid network. Stich a network may result from strong interactions between the surface of the dispersed pa rticles, but softer network may appear if the particles are bound together through the interactions of their surface with polymer chains. In order to analyze and to predict the behavior of nanocomposite materials, a modeling of this type of interactions is proposed, and allows to better understand t he oric,,in of the high reinforcing effect, generally observed. However, th e complete prediction of composite materials with percolating dispersed fil lers is still a difficult problem and requires further developments, It exe mplifies for the special case of composites a general problem of two phase materials: the effect of scaling down the reinforcement and the properties of entangled structures.