e-Polymers 2003, no. 040. ISSN 1618-7229 http://www.e-polymers.org Phase inversion and co-continuity domain in immiscible polyethylene/polystyrene blends Frédéric Prochazka 1 *, Romulus Dima 2 , Jean-Charles Majesté 1 , Christian Carrot 1 1 Laboratoire de Rhéologie des Matières Plastiques, FRE CNRS 2396, Université de Saint Etienne, 23 rue du Dr Michelon, 42023 Saint Etienne Cedex, France; Fax (33)477485126; frederic.prochazka@univ-st-etienne.fr 2 University ‘Politehnica’ of Bucharest, Faculty of Industrial Chemistry, Romania (Received: June 12, 2003; published: August 12, 2003) Abstract: Blends of polystyrene and high-density or linear low-density polyethylene have been prepared in an internal mixer and studied in a wide range of compo- sitions. Phase inversion compositions have been determined using selective extraction and scanning electron microscopy. It appears that phase inversion can occur in a domain of compositions rather than at a single point. The existing models of phase inversion are not complete enough to explain the entire pheno- menon, and percolation of each component may be considered to describe the formation of co-continuity. Introduction On the basis of a simple technology of processing, much more flexible and acces- sible than chemical synthesis, polymer blends offer a good alternative to create new materials. In this kind of materials, the ultimate mechanical properties are greatly influenced by their phase morphology. Controlling this morphology is critical for the performances of the final material [1-2]. In order to be able to predict the morphology, it is important to understand the mechanisms controlling structure evolution under mixing. In the recent years, a lot of experimental and theoretical papers have been published on the fundamental aspects of immiscible blends and their morphology and some of them especially regard the phase inversion phenomenon [3-32]. This critical point corresponds to a region where the two immiscible phases are fully co-continuous and where it becomes impossible to differentiate the matrix from the dispersed phase. Continuity may occur at low volume fractions; it only depends on the shape of the dispersed inclusions. For example, partial continuity, i.e., percolation is possible from 16% (v/v) in the case of spherical droplets but the fraction is much lower for elongated particles. In this case, volume fraction is minimum to obtain percolation, but not the whole material belongs to the percolating structure. Full continuity appears when the entire component becomes part of a single percolating structure. In the last years, many models based on the viscosity ratio of the polymers have been developed to describe the phase inversion process [3-8]. More recently, authors have developed new models considering interfacial tension [9] or elasticity [10]. Anyway, the condition of 1 Unauthenticated Download Date | 11/25/18 7:23 PM