“structured” multi-filler nanocomposites with novel dielectric properties

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Author:
Li, Bo
Graduate Program:
Materials Science and Engineering
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
February 29, 2016
Committee Members:
  • Evangelos Manias, Dissertation Advisor
  • Evangelos Manias, Committee Chair
  • Clive A Randall, Committee Member
  • Michael Anthony Hickner, Committee Member
  • Michael T Lanagan, Committee Member
  • Suzanne E Mohney, Special Member
Keywords:
  • dielectric constant and loss
  • polymer clay composites
  • dielectric breakdown
  • structured composites
  • barrier properties
Abstract:
The focus of the research depicted in this thesis is on how “structuring” polymer-matrix composites can affect, primarily, the dielectric and barrier properties of these composite materials. Structuring is defined as the extra filler distribution or extra composite morphology manipulation, beyond the thermodynamically-dictated filler dispersion. Specifically, polymer-matrix composites with one or more fillers were investigated, and structuring was realized as: high-aspect ratio dielectric nanofiller with high orientation in films; dielectric nanofiller/dielectric microfiller preferential association; dielectric nanofiller/conducting nanofiller preferential association; and sequestration of nanofillers in one phase of an immiscible polymer blend, among others. Both thermoplastic olefin and elastomeric olefin matrices were studied, and in all cases presented here, highly-enhanced materials properties and non-trivial composite performances were designed to originate from the structuring of the composites, i.e., structuring of the composites qualitatively and quantitatively improves the composite properties far beyond what is achievable through the simple dispersion of the same fillers in the same matrix. The origins of this behavior are traced to filler-cluster mechanisms, or synergies between fillers, or filler-cluster effects on the matrix response, specific to each system/structure/property. Given that the volume of current research in these materials is focuses almost exclusively on the dispersion of fillers in a matrix as the route to improve composite performance (primarily by adjusting loading and interfacial parameters), the new knowledge created here on how the composite structuring can yield excess enhancements, extra improvements, or even new properties, opens new directions in the design of, and bears high promise for progress in, these and similar (nano)composite materials, including multi-filler polymer composite and polymer hybrid systems.