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The Effect of Nanoparticle Shape on Polymer-Nanocomposite Rheology and Tensile Strength

Published

Author(s)

Scott Knauert, Jack F. Douglas, Francis W. Starr

Abstract

Nanoparticles can influence the properties of polymer materials by a variety of mechanisms. The molecular dynamics simulations in the present work focus on the case where the modification of the melt structure by glass-formation and entanglement interactions should not be an issue. Since many applications require good particle dispersion, we also focus on the case where the polymer-particle interactions are highly favorable so that relatively good particle dispersion can be achieved. With fullerene, carbon nanotube, and clay or graphene sheet nanocomposites in mind, we investigate how particle shape influences the melt shear viscosity and the tensile strength. Our simulations of model nanoparticle dispersions of compact (icosahedral), tube or rod-like, and sheet- like nanoparticles at a volume fraction 0.05 indicate an order of magnitude increase in the viscosityrelative to the pure melt.This finding evidently can not be explained by continuum hydrodynamics and we provide evidence that the viscosity increase has its origin in chain bridging between the nanoparticles. This increase is the largest for the rod- like nanoparticles and least for the sheet-like nanoparticles. Curiously, the enhancements of viscosity and tensile strength exhibit opposite trends} with increasing chain length N and with particle shape anisotropy. Evidently, the concept of bridging chains alone cannot account for the increase in tensile strength and we suggest that the deformability of the sheet nanoparticles contribute to nanocomposite toughness by reducing the poisson ratio of the composite. Our simulations point to a substantial contribution of nanoparticle shape to both mechanical and processing properties of polymer nanocomposites.
Citation
Journal of Polymer Science Part B-Polymer Physics
Volume
45

Keywords

clay, fullerene, nanoparticles, nanotube, particle shape, poisson ratio, rheology, tensile strength, viscosity

Citation

Knauert, S. , Douglas, J. and Starr, F. (2007), The Effect of Nanoparticle Shape on Polymer-Nanocomposite Rheology and Tensile Strength, Journal of Polymer Science Part B-Polymer Physics, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=852679 (Accessed April 21, 2024)
Created February 22, 2007, Updated October 12, 2021