Nanoparticle Alignment and Repulsion During Failure of Glassy Polymer Nanocomposites

ORAL

Abstract

We investigate crazing and failure in a model nanocomposite of surface modified nanoparticles (cadmium selenide, diameter is 5 nm) blended into polystyrene. We demonstrate that nanoparticles undergo three stages of rearrangement during craze formation and propagation in glassy polymer nanocomposites: 1) Alignment along the precraze, 2) Expulsion from craze fibrils, and 3) Assembly into clusters entrapped between craze fibrils. At an optimal volume fraction of nanoparticles, the failure strain of the nanocomposite is increased by nearly 100{\%} relative to unfilled polystyrene. This optimal volume fraction is related to the balance of two mechanisms: 1) the decrease in cross-tie fibril density for craze structures, and 2) the decrease in the probability of craze widening at higher tensile strain by decreasing the number of polymer entanglements at small interparticle lengths. These results offer a clear and detailed understanding of failure mechanism of glassy polymer-nanoparticle composites, and provide predictions for the future design of nanoparticle-based materials.

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Authors

  • Alfred Crosby

    Polymer Science and Engineering Department, University of Massachusetts, Amherst, University of Massachusetts Amherst, University of Massachusetts-Amherst

  • Jong-Young Lee

    University of Massachusetts Amherst

  • Qingling Zhang

    Polymer Science and Engineering Department, University of Massachusetts Amherst, University of Massachusetts, Amherst, University of Massachusetts Amherst, Department of Polymer Science \& Engineering, University of Massachusetts, Amherst, MA 01003, USA

  • Todd Emrick

    Polymer Science and Engineering Department, University of Massachusetts Amherst, Department of Polymer Science \& Engineering, University of Massachusetts, Amherst, MA 01003, USA, University of Massachusetts, Amherst, University of Massachusetts Amherst, University of Massachuestts Amherst, Polymer Science and Engineering, University of Massachusetts, Amherst