A study on the interactions between silica modified with different coupling agents and elastomers used for tyre treads

In the present contribution we present the results of a study aimed to investigate the influence of different modifying agents on the interactions between silica and elastomers and, then, on the dispersibility of the filler in the elastomeric compounds. A precipitated silica was treated with TESPT, octadecyltriethoxysilane (ODTES) and mixtures of TESPT/ODTES of different compositions; the degree of modification was determined by elemental analysis. Inverse gas chromatography (IGC) at infinite dilution was used to evaluate surface characteristics of the silica (stationary phase) and to calculate the adsorption free energy and enthalpy of low molecular weight hydrocarbons, analogues of elastomers (eluates). Vulcanized SBR based compounds loaded with different amounts of silica both unmodified and modified were investigated by transmission electron microscopy (TEM) and automated image analysis (AIA) to determine the dispersion of the filler within the matrix as well as to achieve quantitative information on aggregate size and shape distribution of silica and, consequently, on the polymer-filler interactions. A satisfactory agreement between thermodynamic predictions and the preliminary results from morphological analysis has been obtained.