REINFORCEMENT OF SILOXANE ELASTOMER WITH POSS BASED FILLERS
Inorganic-organic hybrid materials can provide excellent combined properties. And when the length scale of the component phase approaches nanometers, the expected global properties will be more strongly affected by interfacial interactions rather than bulk phase properties. Polyhedral oligomeric silsesquioxane (POSS) is an entirely new inorganic component that has defined structure and functional groups; thus POSS opens the possibility of preparing nanocomposites with controlled morphology and tailored interfaces. POSS systems can be developed to elucidate the effect of the structure and interfacial bonding on polymer microstructure and the resulting effects on macroscopic properties. The first section of this thesis reports the use of monovinyl POSS as a building block to make controlled-structure materials. Four POSS cages with vinyl groups were linked to a central siloxane core using a hydrosilylation reaction. The hydrosilylation reaction was monitored using fourier-transform infrared spectroscopy (FT-IR) and proton nuclear magnetic resonance (1H-NMR). The resulting structure was confirmed by mass spectroscopy (MALDI-MS). In the second section, POSS was incorporated into poly(dimethylsiloxane) (PDMS) physically and chemically to investigate the effect of polymer-filler bonding. For physically blended composites, single POSS molecules and the molecules with up to four connected POSS (tetraPOSS) were used. The goal was to investigate the size effect on the reinforcement. In the chemically-bonding system, vinyl terminated PDMS was used; therefore, some POSS molecules were attached to the network through the hydrosilylation reaction. Both tensile tests and dynamic mechanical analysis showed that simply blending these POSS-based fillers into silanol-terminated PDMS had little effect on its mechanical properties, but bonding them to the PDMS provided considerable reinforcement. Based on these results, it seems that the reinforcement results not from direct bonding, but rather from the improved dispersion that indirectly results from bonding.
School:University of Cincinnati
School Location:USA - Ohio
Source Type:Master's Thesis
Keywords:polyhedral oligomeric silsesquioxane siloxane elastomer nanocomposites mechanical properties reinforcement
Date of Publication:01/01/2003