Rheological behavior of nanofillers enclosed multilayer systems under elongational flows: From microlayers to nanolayers

Abstract

Abstract. The present work dedicated in the elongational behavior of multilayer polymer nanocomposites. CNTs were enclosed in a polypropylene with linear chain structure (PPC) and then co-extruded with another polypropylene (PPH) with long chain branching (LCB). By forced assembly, multilayer films with layer thickness from micro to nano were fabricated and the elongational rheology test was then conducted with the extension vertical to the film extrusion direction. Due to the LCB inside PPH, all multilayer films showed obvious strain hardening behavior despite linear PPC is a strain softening polymer. When the layer numbers were fewer, namely, the layer thickness was higher than the length of the CNTs, the strain hardening behavior of nanocomposite films was close to the multilayer system with neat polymers. With the layer numbers increasing, the layer thickness became lower than the length of the CNTs and the strain hardening behavior of nanocomposite films increased dramatically compared to the multilayer system with neat polymers. The reason for this kind behavior was because of the better orientation of CNTs via layer confinement when layer numbers increased, which thus making the strain hardening more significant.