Kyriaki Kalaitzidou

A Route for Polymer Nanocomposites with Engineered Electrical Conductivity and Percolation Threshold

Polymer nanocomposites with engineered electrical properties can be made by tuning the fabrication method, processing conditions and filler’s geometric and physical properties. This work focuses on investigating the effect of filler’s geometry (aspect ratio and shape), intrinsic electrical conductivity, alignment and dispersion within the polymer, and polymer crystallinity, on the percolation threshold and electrical conductivity of polypropylene based nanocomposites. The conductive reinforcements used are exfoliated graphite nanoplatelets, carbon black, vapor grown carbon fibers and polyacrylonitrile carbon fibers. The composites are made using melt mixing followed by injection molding. A coating method is also employed to improve the nanofiller’s dispersion within the polymer and compression molding is used to alter the nanofiller’s alignment.

Adaptive polymer particles

Adaptable polymer particles that can change geometry, flow characteristics, and adsorption properties upon the stimulation of an environmental change, such as temperature, are fabricated by utilizing the residual stress developed at the interface of a bilayer. We propose a phase diagram that can be used to predict the shape and size of the adaptive polymer particles as a function of the material modulus, thickness ratio, and the bilayer’s lateral dimensions. The materials used are gold/titanium and polydimethylsiloxane, but the method is applicable to a wide range of material combinations. Initial demonstrations of this responsive control and its impact on properties of the adaptive polymer particles are also presented.