Innovative Mesoporous Nanosilicas: SBR Nanocomposite for Low Environmental Impact Tread Tyre.

Silica nanoparticles with different aspect ratios (A.R.) were tested as reinforcing fillers of styrenebutadiene copolymer (s-SBR) for "green tyres," i.e., tires with lower rolling resistance. A commercial nanosilica with A.R. = 1 (Aerosil® 200) was compared with two nanosilica samples with A.R. = 2 and 4, synthesized by means of an innovative process, to ascertain if the filler shape was significant to improve the composite properties. In addition, bis-triethoxysilylpropyltetrasulfide was grafted onto the particles surface, in order to obtain more hydrophobic materials and to enhance their dispersion in the elastomeric composites: pristine and modified silicas were then compared. Grafting extent was evaluated by thermogravimetric analysis. The surface properties of silicas were investigated by Fourier transform infrared spectroscopy and inverse gas chromatography. s-SBR/silica nanocomposites were then prepared and characterized assessing their dynamic-mechanical properties and carrying out morphological observations by transmission electron microscopy.

Influence of the silane modifiers on the surface thermodynamic characteristics and dispersion of the silica into elastomer compounds.

A good dispersion of silica into elastomers, typically used in tire tread production, is obtained by grafting of the silica with multifunctional organosilanes. In this study, the influence of the chemical structure of a triethoxysilane (TES), octadecyltriethoxysilane (ODTES), and ODTES/bistriethoxysilylpropyltetrasulfane (TESPT) mixture was investigated by inverse gas chromatography (IGC) at infinite dilution. Thermodynamic results indicate a higher polarity of the silica surface modified with TES as compared to that of the unmodified silica due to new OH groups deriving from the hydrolysis of ethoxy groups of the silane; the long hydrocarbon substituent of the ODTES lies on the surface of silica and reduces the dispersive component of the silica surface tension. A comparison with silica modified with TESPT is discussed. An accurate morphological investigation by transmission electron microscopy (TEM) and automated image analysis (AIA) was carried out on aggregates of silica dispersed into a SBR compound loaded with 35 phr (per hundred rubber) of untreated and TESPT-treated silica. Morphological descriptors such as the projected area/perimeter ratio (A/P) and roundness (P2/4piA) provided direct and quantitative indications about the distribution of the filler into the rubber matrix.