Depercolation of aggregates upon polymer grafting in simplified industrial nanocomposites studied with dielectric spectroscopy
The dynamics of polymer and filler in simplified industrial silica-styrene-butadiene nanocomposites (silica Zeosil 1165 MP, volume fraction 0-21%v) have been studied with broadband dielectric spectroscopy (BDS) and nuclear magnetic resonance (NMR). The fraction of graftable matrix chains was varied...
| Autores: | , , , , , |
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| Tipo de recurso: | artículo |
| Fecha de publicación: | 2015 |
| País: | España |
| Institución: | Consejo Superior de Investigaciones Científicas (CSIC) |
| Repositorio: | DIGITAL.CSIC. Repositorio Institucional del CSIC |
| OAI Identifier: | oai:digital.csic.es:10261/136347 |
| Acceso en línea: | http://hdl.handle.net/10261/136347 |
| Access Level: | acceso abierto |
| Palabra clave: | Percolation Polymer grafting Nanocomposites Dynamics |
| Sumario: | The dynamics of polymer and filler in simplified industrial silica-styrene-butadiene nanocomposites (silica Zeosil 1165 MP, volume fraction 0-21%v) have been studied with broadband dielectric spectroscopy (BDS) and nuclear magnetic resonance (NMR). The fraction of graftable matrix chains was varied from 0 to 100%D3. The introduction of silica nanoparticles is shown to leave the segmental relaxation unaffected, an observation confirmed by the measurement of only a thin (some Angstroms thick) immobilized layer by NMR. The low-frequency measurements are resolved in two distinct dielectric Maxwell-Wagner-Sillars (MWS) processes of different behavior with respect to changes of large-scale silica structures induced by variations of filler fraction and grafting. It is found that increasing grafting leaves the first MWS-process unaffected, while it decreases the strength of the (slower) second MWS by about a decade. At constant silica volume fraction, this indicates depercolation of the filler, thereby providing a microscopic explanation of the evolution of rheological reinforcement. The sensitivity to large-scale reorganizations together with a characterization of local polymer dynamics provides insight over many length- and time-scales into structure and dynamics of nanocomposites, and thus the physical origin of the reinforcement effect. |
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