ABSTRACT
ABSTRACT: Several mechanisms have been proposed to explain the remarkable mechanical properties of elastomers filled with sub-micrometric particles. The complexity of their structure and dynamics has been evidenced through many experimental techniques. Understanding and discriminating the various reinforcement mechanisms is a key issue in the field. We shall present an approach in which the response of the elastomer matrix in a filled elastomer material is selectively observed. Different, complementary techniques are combined, namely measurements of the mechanical response in conjunction with measurements of chain segment orientation by X-ray scattering, in which the response of the elastomer matrix is selectively obtained. Crosslink densities are measured independently by multiple-quantum proton NMR. In unfilled materials, all measurements are nicely correlated, in full agreement with rubber elasticity theory. In filled materials, analyzing the deviations with respect to the behavior of the pure unfilled elastomer matrix allows discriminating chain over-stretching (entropic contribution to reinforcement) and rigid network effects (non-entropic contribution to reinforcement). The relative contributions of each mechanism are discussed, as a function of temperature, filler fraction and strain amplitude, in various elastomer materials filled with precipitated silica.
