Deformation of Matrix-Free, Glassy Single Component Polymer NanoComposite at Extreme High Strain Rates

Very thin, freestanding glassy polystyrene (PS) films show unexpectedly large energy absorption under rapid axisymmetric tensile loading at ballistic strain rates (~ 10⁷/s). For supersonic microprojectile (3.7 μm diameter) impact (350~800 m/s), the more mobile and less entangled near-surface regions of the PS facilitate crazing and dramatically increase craze multiplication and subsequent growth with accompanying large adiabatic temperature rise of the highly deforming film. Here, we investigate the influence on the high rate deformation of grafting of the PS chains to nanoparticle (NP) surfaces. The covalent anchoring of several hundred polymer chains to individual silica NPs and the well-entangled coronal regions between NPs improve the stress transfer through the composite, yielding polymer nanocomposites with excellent energy absorption. The single component nanocomposite PS grafted nanoparticle (PSgNP) films (~ 1% v/v, 16nm diameter SiO₂ NPs) show 25% enhanced high kinetic energy absorption per unit mass of the target film over the previous record specific energy absorption of the thin, freestanding homopolymer PS films.