In situ sol–gel obtained silica–rubber nanocomposites: influence of the filler precursors on the improvement of the mechanical properties

Abstract

Silica-rubber nanocomposites were obtained by in situ sol-gel synthesis, using trialkoxysilanes with different functional groups as precursors. The functionalities were selected in order to favor the formation of differently shaped silica particles and/or to modulate the filler-filler and the filler-rubber interactions. The functional groups included (a) alkyl and alkenyl groups: triethoxy(vinyl) (VTEOS), triethoxy(propyl) (PTEOS), triethoxy (octyl) (OCTEOS); (b) N-containing alkyl groups: triethoxy(3-aminopropyl) (APTEOS), triethoxy(3-cyanopropyl) (CPTEOS), triethoxy(3-propylisocyanate) (ICPTEOS); (c) S-containing alkyl groups: trimethoxy(3-mercaptopropyl) (TMSPM), bis(3-triethoxysilylpropyl) disulfide (TESPD), bis(3-triethoxysilylpropyl) tetrasulfide (TESPT); triethoxy(3-octanoylthio-1-propyl) (NXT). Transmission electron microscopy(TEM) investigation suggested a relationship between the morphology of the filler network and the used trialkoxysilanes, as a function of the particle shape and of the interaction of the particle surface groups between them and with the matrix. The dynamic-mechanical properties of nanocomposites, both uncured and vulcanized, were discussed in relation to the network morphology, suggesting a connection between the used silica precursors and the functional properties. The filler-rubber interaction due to substituents which chemically interact with the polymer, promotes the homogeneous distribution of the silica particles in the matrix, while the filler-filler interaction, favored by the shape induced physical interactions or by the chemical interaction among surface groups, mainly contribute to the filler networking and to the dynamicmechanical properties of the composites.

Silica nanoparticles reinforced natural rubber latex composites: The effects of silica dimension and polydispersity on performance

“…After modification with TESPT, the decreased surface polarity of silica will be the major contribution factor to both the higher bound rubber contents and stronger interaction between the filler and nonpolar rubber. Considering all the experiment results above, it is consistent with the theory that spherical silica particles with homogenous size and continuous networks strengthen rubber reinforcement …”

“…For silica/NR compound prepared by latex compounding technique, several attempts have been made to explore the feasible and advantageous process. First, the in situ silica particles prepared by in situ sol–gel method with silica precursor, and then co‐flocculated with rubber latex has been reported . Meanwhile, many efforts have been carried out focusing on the silica reinforce rubber in latex system by sol–gel method as well .…”

Effect of silane integrated sol–gel derived in situ silica on the properties of nitrile rubber

“…The amount of organosilane has been varied to assess its influence on the properties of the composites. Similar approaches of in situ silica generation along with different organosilanes in NR latex and aminopropylsilane in epoxidized SBR solution were reported . Properties of all the synthesized composites were evaluated in terms of curing characteristics, morphology, mechanical and dynamic mechanical properties.…”

Hybrid SiO2@POSS nanofiller: a promising reinforcing system for rubber nanocomposites

“…[1][2][3][4][5][6] In this context, we reported that the fine tuning of size and shape in silica nanoparticles (NPs), along with their surface organic functionalization, favors filler interaction with the polymer and allows the formation of a homogeneous and continuous percolative filler network which enhances the mechanical properties of the ensuing composites. 7,8 Recently, we also demonstrated that particles having an anisotropic shape are able to self-assemble in nanostructures inside the rubber matrix, providing an increase of the rubber immobilized at the filler/rubber interface and a consequent improvement of the mechanical properties. 9 These results suggest that the utilization of fillers with tailored structures and functionalities, able to simultaneously improve the filler networking and the filler-rubber interaction, increasing the amount of immobilized rubber, is a promising approach to obtain better mechanical properties of the composite and to limit the silica amount during compounding.…”