The filler–rubber interface in styrene butadiene nanocomposites with anisotropic silica particles: morphology and dynamic properties

Abstract

Silica-styrene butadiene rubber (SBR) nanocomposites were prepared by using shape-controlled spherical and rod-like silica nanoparticles (NPs) with different aspect ratios (AR = 1-5), obtained by a sol-gel route assisted by a structure directing agent. The nanocomposites were used as models to study the influence of the particle shape on the formation of nanoscale immobilized rubber at the silica-rubber interface and its effect on the dynamic-mechanical behavior. TEM and AFM tapping mode analyses of nanocomposites demonstrated that the silica particles are surrounded by a rubber layer immobilized at the particle surface. The spherical filler showed small contact zones between neighboring particles in contact with thin rubber layers, while anisotropic particles (AR > 2) formed domains of rods preferentially aligned along the main axis. A detailed analysis of the polymer chain mobility by different time domain nuclear magnetic resonance (TD-NMR) techniques evidenced a population of rigid rubber chains surrounding particles, whose amount increases with the particle anisotropy, even in the absence of significant differences in terms of chemical crosslinking. Dynamic measurements demonstrate that rod-like particles induce stronger reinforcement of rubber, increasing with the AR. This was related to the self-alignment of the anisotropic silica particles in domains able to immobilize rubber.

Effects of modified silica on the co‐vulcanization kinetics and mechanical performances of natural rubber/styrene–butadiene rubber blends

“…From Figure (a), large SiO 2 agglomerates are found in rubber matrix. After being modified by silane and vulcanization accelerator CZ, the filler‐filler interaction was dramatically weakened and the compatibility between filler and rubber was improved . Hence, m‐SiO 2 and SiO 2 ‐s‐CZ can be uniformly dispersed in rubber blends as shown in Figure (b,c), respectively.…”

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

“…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.…”

Local and Global Dynamics in Polypropylene Glycol/Silica Composites

“…Addition of silica nanoparticles was reported to reduce the intensity of the glass transition of poly-2-vinylpyridine due to restricted segmental mobility of polymer segments at the interface [40]; on the other hand, for silica nanocomposites of polyvinylacetate no change was observed in the magnitude of the property changes at Tg, beyond that due to the replacement of polymer by the filler [41]. Atomic Force Microscopy showed restricted mobility for styrene-butadiene copolymer at the interface with silica particles [42].…”