Date of Award

Summer 8-2012

Degree Type

Masters Thesis

Degree Name

Master of Science (MS)

Department

Polymers and High Performance Materials

Committee Chair

Sarah Morgan

Committee Chair Department

Polymers and High Performance Materials

Committee Member 2

Robson Storey

Committee Member 2 Department

Polymers and High Performance Materials

Committee Member 3

Robert Lochhead

Committee Member 3 Department

Polymers and High Performance Materials

Abstract

The goal of this thesis was to define the structural factors that determine performance in clay/rubber nanocomposites when polyhedral oligomeric silsesquioxane (POSS) is used as a dispersant. POSS has been shown previously to enhance clay, metal oxides, and carbon nanotube dispersion in thermoplastics matrices, but their performance in rubber systems has not yet been explored. There is little fundamental understanding of how POSS interacts with clay and how these modified fillers react with rubber matrices. This thesis aims to develop a greater understanding of the mechanisms of POSS-clay modification through the examination of two different POSS-clay systems and their effect on rubber matrices with varying functional groups. In this thesis, an amino-based, closed cage POSS and an open-caged trisilanol POSS were used as modifiers of montmorillonite clay. A commercially avai lable, organically modified clay was used as a control. These fillers were studied as a function of loading level in a hydrogenated nitri le butadiene rubber and a styrene butadiene rubber matrix. Both POSS systems successfully grafted onto the clay particles; however, the closed cage POSS produced an expanded interlayer spacing. The open cage POSS produced small particles with an increased surface area. When introduced into rubber matrices, both POSS-modified clay systems produced nanocomposites with improved properties. The trisilanolphenyl POSS-clay filler provided a 7°C increase in degradation temperature, 136% increase in tensile modulus and an 800% improvement in storage modulus. Differences in performance are attributed to the cage structure, functional groups, and chemical and physical interactions of POSS with the rubber molecules.

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