JEC COMPOSITES MAGAZINE - Issue #41 - June 2008 - 67

KNOW-HOW Control Visiovis: monitoring nanofiller dispersion/ distribution in molten polymers The intimate mixture of nanofillers and polymers leads to an extraordinarily extended interface. However, the greatest advantage of nanocomposites becomes the main driving force for filler aggregation. This is unfortunate, as the ability to disperse nanofillers in polymers is a strict requisite for any profitable commercialization of nanocomposites. Filler aggregation depends on the physico-chemical interactions between the particles, i.e. on particle dimensions (specific surface) and surface treatment. Filler dispersion and distribution into the matrix depend on processing efficiency. Dispersion is related to the physical separation (isolation) of the elementary particles, and distribution deals with the ability of the particles (whether isolated or aggregated) to occupy the Fig.2: Possible aggregation and/or distribution whole space of the outcomes in composite materials. Good distribution but poor dispersion (a), matrix in a homopoor distribution and poor dispersion (b), geneous manner poor distribution but good dispersion (c), good distribution and good dispersion (d) (figure 2). 1- ANTONELLA ESPOSITO, PH.D. STUDENT 2- JEAN BALCAEN, TECHNICIAN 3- JANNICK DUCHET-RUMEAU , ASSOCIATED PROFESSOR 3- JEAN-YVES CHARMEAU, PROFESSOR UNIVERSITÉ DE LYON, LABORATOIRE DES MATÉRIAUX MACROMOLÉCULAIRES (LMM/IMP) UMR CNRS 5223, INSTITUT NATIONAL DES SCIENCES APPLIQUÉES INSA LYON dding fillers to polymers greatly improves their properties [1]. The revolution of nanofillers starts with the intimate mixture of their elementary particles with matrix macromolecular chains, which produces an extraordinarily extended organic-inorganic interface [2]. The greatest advantage of nanocomposites becomes the main driving force for filler aggregation, however: the higher the specific surface, the stronger the interactions between filler moieties and the more favoured their aggregation will be. Aggregates in composite materials can cause premature failure (figure 1) and modify the micromechanical behaviour in an unpredictable manner. Polymer-clay nanocomposites Clays were originally supposed to reinforce polymers in the form of micro-sized clusters. However, the results were not much better than those obtained for traditional composites, because clusters do not have the same properties as a single platelet [4]. Clay layers interact weakly with each other, diminishing the mechanical resistance locally and contributing to the formation and propagation of cracks. Polymer-clay nanocomposites only became marketable some time after the registration of the first industrial patents [4]; the ability to properly and reproducibly Fig.1: Influence of nanofiller distribution on the micromechanical behaviour of composite materials [3] Fig.3: Clay multiscale structure [5] No41 June 2008 / JEC Composites Magazine

JEC COMPOSITES MAGAZINE - Issue #41 - June 2008

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #41 - June 2008