Single wall carbon nanotubes (SWNTs) have attractive inherent mechanical properties with measured tensile strength and modulus up to 45 GPa and 750 GPa, respectively. Furthermore, the low density of SWNTs (1.3 - 1.6 g/cm3) makes them an excellent candidate to be used as filler in polymer composites for structural and reinforcement applications. SWNTs also have exceptional optical, thermal and electrical properties that would allow production of multifunctional composites. However, most studies show that macroscopic continuous CNT-based composites have relatively low mechanical properties. The main challenges to produce high-performance polymer nanocomposites relate to achieving; (a) high CNT individualization, (b) high CNT orientation, and (c) high polymer-CNT interfacial shear strength (IFSS), while attaining high CNT loading in the polymer. In this contribution, the above-mentioned challenges will be discussed, along with the use of poly(methyl methacrylate) (PMMA) as a non-covalent method to reach CNT individualization in solution and in solid CNT films and fibers, as well as in their composites. PMMA creates an ordered helical wrap that stabilizes dispersions of individual SWNTs. This behavior contradicts previous modeling predictions that indicated: i) flexible chains with bulky side-groups such as PMMA adsorb by inter-chain coiling on the SWNT surface and, ii) ordered wrapping behavior is mostly observed from rigid polymers with aromatic moieties. Following the PMMA helical wrapping approach on SWNTs, poly(acrylonitrile-co-methacrylic acid) fibers with 1 and 5 wt.% SWNT were processed by dry-jet wet spinning, while also varying the molecular weight of the PMMA. Processing, structure, and properties of these fibers were studied and compared to similar nanocomposite fibers processed without PMMA wrapping. Nanocomposite fibers with PMMA-wrapped SWNT had IFSS 47% larger (up to 47.5 ± 3.2 MPa) as compared to the corresponding fibers with SWNTs that were not wrapped with PMMA. Further strategies to improve reinforcement efficiency of composite polymer fibers using this non-covalent dispersion method will also be discussed.

Noncovalent ordered wrapping of poly(methyl methacrylate) on single-wall carbon nanotubes and its effect on macroscopic-continuous polymer composite fibers

2019 Fall National Meeting

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