Ultrasound-assisted-pressure-induced-flow leading to superior polymer/carbon nanotube composites and foams

Abstract

In the presented work, nano-sized carbon particles were coated onto the surface of semicrystalline polymer pellets and molded into an intermediate preform, with a honeycomb-like structure, at elevated temperatures and pressures. The preforms were further processed through pressure induced flow (PIF) at higher pressures or ultrasound assisted pressure induced flow (UAPIF) at lower pressures to achieve polymer nanocomposites with a co-continuous and ‘brick and mud’ structure. The particle-coated polymer pellets, preforms, and composites can be saturated or partially saturated with a blowing agent, so foaming may occur during or after molding to fabricate polymer nanocomposite foams with a layer-by-layer bimodal cell structure. Using polypropylene and carbon nanotubes as an example, and carbon dioxide as the blowing agent, we show that these new materials can provide superior mechanical and physical properties with good electrical conductivity and foam expansion ratio, not achievable by conventional nanocomposites and foams with the same composition.