49Applied RheologyVolume 15 · Issue 1

ConferenceReport III

39th Meeting of the French Rheology Group (GFR)

13.-15.10.2004Mulhouse, France

The 39th meeting of the French Rheology Group(GFR) has been held in Mulhouse from October13th to 15th 2004. The topic of the meeting was“Rheology and Interfaces”. Members of the Lab-oratoire de Physique et Mécanique Textiles andof the Institut de Chimie des Surfaces et Inter-faces have been associated in the organizingcommittee. One of their objectives was to pro-mote exchanges and discussions between spe-cialists of rheology and of physical-chemistry ofsurfaces and interfaces. More than 130 scientistsfrom academic and industrial laboratories haveattended the meeting. The presence of exhibi-tion stands of nine companies allowed every-body to discover the last developments of mea-surement techniques both in rheology (AntonPaar, Malvern, MTS Systèmes, Sodexim, Swan-tech, TA Instruments, Thermo Electron) andinterfacial measurements (Krüss, GBX Instru-ments).

Each day was introduced by a plenarylecture. The first, given by Pierre Attané from theLaboratoire de Rheologie of Grenoble University,concerned the influence of the rheology of inksin the continuous printing ink jet process. Heshowed the importance of characterization ofthe inks at high frequencies and of the measure-ment of the transient elongational viscosity.Then, it is necessary to use non-conventionalrheometers specially designed for this purpose.David Quéré (Collège de France) presented thesecond lecture entitled: The liquid-liquid impact:the art of samovar. He discussed the air drawingwhen the velocity exceeds a critical value and hepresented very fascinating experiments. Thethird lecture was proposed by Guy Nemoz (Insti-tut Français du Textile et de l’Habillement, Lyon).He gave a large synthesis on the rheology in tex-tile processes including spinning of polymermelts, coating, impregnation of textiles, ageingof materials such as geotextiles or membranesfor architecture.

The general topics of the conference“Rheology and Interfaces” covers a wide varietyof problems and opens research fields as it hasbeen shown through the 33 oral communicationsand the 35 posters which have been presented.An analyze of the contents of the papers showsthat different kinds of interfaces have been con-sidered: liquid-gas, liquid-liquid, liquid-solid,solid-solid. Then, several families of materials are

explored: foams, emulsions, eventually filledwith solid particles, dispersions, and granularmedia. The study can be done at different scalesfrom macro-, micro- to nano- and molecular one.Experimental research in that field often com-bines conventional rheometry and other mea-surement techniques, especially spectroscopy orimaging. Instruments are also specially designedfor the rheology of thin films or materials in aconfined space and some papers were at theinterface between rheology and tribology ornano-tribology.

The knowledge of the mechanical prop-erties of thin films and of membranes has a greatimportance in a lot of applications such as, forinstance, lubrication or design of adhesives. Sev-eral contributions concerned the measurementof the rheological properties of materials in con-fined geometries by means of a piezorheometeror a surface force apparatus. Experimental dataon interfacial rheology measurements have beenreported. It mainly concerns the thin layer of sur-factants adsorbed at the interface between twoliquids or air and a liquid. The main technique isbased on the bi-cone geometry. Other devicesuse the oscillating magnetic needle and the oscil-lating pendent drop to get the shear surface andthe dilational surface rheological properties.

Granular media and powders involvesolid-solid interfaces. Rheometry of powdersrequires specific instruments and a new powderrheometer has been presented. Phenomena suchas particle segregation and migration are oftenimportant in the flow of such materials as wellas in concentrated suspensions and the localstructure is studied through imaging techniques(fluorescence, NMR, flow visualization with trac-ers) or spectroscopy. For very turbid media, a lotof information could be obtained by multiplepolarized light scattering. IR thermography asso-ciated with speckle correlation gives an approachof the thermomechanical behavior of a polymer.The rheological properties of complex materialssuch as suspensions of solid particles in polymersolutions or in emulsions depend on the parti-cle/fluid interfaces in the bulk. Several papersconcern these problems, for instance, in the caseof ceramic pastes, bentonite suspensions in poly-mer solutions, cements, self-compacting con-crete pastes, suspensions of fibers with adhesivecontacts.

Applied Rheology Vol.15-1.qxd 18.03.2005 13:22 Uhr Seite 49

This is an extract of the complete reprint-pdf, available at the Applied Rheology websitehttp://www.appliedrheology.org

This is an extract of the complete reprint-pdf, available at the Applied Rheology websitehttp://www.appliedrheology.org

50 Applied RheologyVolume 15 · Issue 1

Rheological measurements are oftencoupled with rheo-optical ones. It is the case forthe study of shear banding or of shear-inducedstructures in micellar solutions but also to inves-tigate the coalescence, deformation and break-up of droplets in compatibilized polymer blends.Problems occurring in polymer melt processinghave been treated either from experimentalapproach or numerical simulation such as forinterfacial instabilities during the co-extrusion ofcompatible polymers. What happens at thematerial/flow device interface? This topics hasalso been considered by several participants inthe case of granular media, of emulsions but alsofor simple liquids on smooth model surface forwhich experiments based on Near field LaserVelocimetry show that the assumption of no slip-ping at the wall is not so evident.

Posters owners and companies weregiven a short time to present their work or mate-rial during a special session. This certainly con-tributes to promote busy discussions. On Wednes-day evening, an official welcome reception wasoffered at the Columns Hall of Mulhouse Town

Hall. It was the opportunity to discover a part ofMulhouse history. The Swiss cantons coats-of-arms are represented on the frescoes of the wallsof the town hall. It is a memory of the time whenMulhouse was a small republic allied with Switzer-land (until the beginning of 19th century). For his-torical reasons, this situation promoted the widedevelopment of textile manufactories, especiallyfor textile printing. Thursday afternoon, a visit ofthe National Automobile Museum-Schlumpf col-lection was organized, followed by a drink in theenvironment of sumptuous cars (Bugatti Royale,…) and by the conference dinner during whichthree awards have been conferred.

On Friday morning, the next GFR meet-ing has been presented by P. Navard (Sophia-Antipolis) and rendezvous is given to the rheolo-gists at Nice in October 2005.

Dominique DupuisENSITM/LPMT11 rue A. Werner68093 Mulhouse cedexd.dupuis@uha.fr

Applied Rheology Vol.15-1.qxd 18.03.2005 13:22 Uhr Seite 50

This is an extract of the complete reprint-pdf, available at the Applied Rheology websitehttp://www.appliedrheology.org

This is an extract of the complete reprint-pdf, available at the Applied Rheology websitehttp://www.appliedrheology.org