The Role of Elongational Flow in Morphology Modification of Polyethylene/OMMt Nanocomposite System

Abstract

The formulation of high-performance polymer based nanocomposites depend on many factors, such as polymeric matrix type, nanoparticle type, loading and morphology, affinity between the polymeric matrix and nanoparticles, presence of compatibilizer and processing conditions [1-4]. During the industrial processing the polymer based systems are subjected to two different processing flows, i.e. the shear and elongational flow. The shear flow plays a significant role in polyethylene/OMMt manufacture processing but it is not able to change the system morphology, while, the elongational flow, involved in spinning and film-blowing processing operations, can induce considerably clay morphology variations [5-13]. In order to evaluate the effect of the elongational flow on the polyethylene/OMMt system morphology, the affinity between the matrix and the OMMt particles can be considered. In particular, the presence of some compatibilizer, as maleic anhydride grafted polyethylene can modify the system affinity and subsequently, the clay morphology changes are different than the uncompatibilized system also upon the extensional flow. Nevertheless, the obtained morphology changes upon the elongational flow in the polyethylene/OMMt system, without and with good system affinity, lead to significant mechanical improvements than the unfilled systems, more larger than the simple macromolecular orientation [10, 12]. If considering, from “flow point of view”, the polyethylene/OMMt system as a biphasic incompatible mixture, composed by an inorganic phase dispersed in a polymeric matrix, the applied extensional flow can be able to change strongly the clay morphology. In particular, the clay nanoparticles can be broken and/or fragmentized, dispersed and oriented along the flow direction, giving rise to flow induced intercalation/exfoliation morphology transition. Indeed, the OMMt particles can be considered as hard but breakable particles, i.e. polymeric particles in a polymeric blends, while, the conventional filler particles are elastic but unbreakable. The elongational flow leads to exfoliation of intercalated OMMt tactoids and/or to some more intercalation of the same tactoids. For the systems with good affinity