(227c) Mechanical Properties of Nanocomposite Systems

Particulate fillers, such as silica, carbon black and calcium carbonate, are widely used in polymer industry to improve material properties.Because of the increasing technological applications a large extent of research has been focusing on nanocomposite properties. The interaction zone and the bridge formation hypotheses are often used to explain the changes in mechanical properties that accompany the addition of nanoparticles to a polymer matrix. In the melt regime we employ a formalism that relies on a rouse mode analysis to study the local mechanical properties of nanocomposites. In the glass regime the elastic constants are calculated through local stress fluctuations and the non affine displacement field is determined. Advanced Monte Carlo techniques involving chain connectivity altering algorithms are used to create statistically independent configurations. Attractive polymer particle interactions are considered for different chain lengths. An increase of the mechanical properties is found which exhibits a dependence on chain length. The formation of a stiffer glassy layer is apparent in the vicinity of the nanoparticles validating the interaction zone theory. Calculation of chain bridges between the particles is compared to the chain length to examine the bridge formation hypotheses. The distribution of local moduli and the correlation of the non affine displacements give interesting results on the inhomogeneity and the fragility of the nanocomposite and the unfilled polymer systems.