AGASSANT , Jean-François

Drawing instabilities and rupture are a serious limitation in polymer fibre and film processing. Draw resonance and fibre or film rupture depend on the processing conditions, heat transfer and on the rheology of the polymer and some of these defects may also be encountered for Newtonian fluids. This paper reviews the different instabilities...

Drawing instabilities and rupture are a serious limitation in polymer fibre and film processing. Draw resonance and fibre or film rupture depend on the processing conditions, heat transfer and on the rheology of the polymer and some of these defects may also be encountered for Newtonian fluids. This paper reviews the different instabilities...

Health regulations are becoming increasingly restrictive which leads to develop solvent free laminating processes. Hot melt adhesives represent an interesting solution to bond two pre-printed substrates of polymer for packaging applications for example, but their high viscosities require extruding the polymer formulation through important die...

The film casting process is widely used to produce polymer film: a molten polymer is extruded through a flat die, then stretched in air and cooled on a chill roll. This study is devoted to the extensional flow between the die and the chill roll. The film shows a lateral neck-in as well as an inhomogeneous decrease of the thickness. An...

Film casting process is widely used to produce polymer film: a molten polymer is extruded through a flat die, then stretched in air and cooled on a chill roll. This study is devoted to the extensional flow between the die and the chill roll. The film shows a lateral neck-in as well as a inhomogenous decrease of the thickness. Thickness as well...

An important problem arising in the cast film process is the socalled neck-in phenomenon, which may induce a drastic film width reduction as well as an inhomogeneous film thickness distribution (with the so called "dog-bone" defect on each side of the film). This neck-in phenomenon is highly influenced by the polymer rheology (increasing...

Interfacial instabilities occurring in the coextrusion process of molten polymers have been widely studied. The theoretical work based on the stability of 2D Poiseuille multilayer flows (invariant along the flow motion) have pointed out the convective nature of this instability (it is either amplified or damped in the flow direction). This...

Film blowing, as other elongational polymer forming processes, may present marked drawing instabilities leading to unacceptable products. But in film blowing, these instabilities are much more complex than for example in fibre spinning: there is no stabilizing effect of the polymer cooling, and the symmetry of the process may be broken, leading...

Polyurethane (PU) foams are widely used in construction, automotive industry, household appliances and other fields. Their low weight and excellent mechanical and thermal insulation properties result from their internal structure. They are sometimes associated to other components to get new polyurethane composites. Structures made from...

A key problem in the modeling of polyurethane (PU) foaming is the determination of relevant physical parameters for the viscosity, the gas expansion, and the curing rate. Indeed, it is difficult to measure the chemical kinetics parameters as well as the viscosity of industrial PU formulations (polyol–isocyanate–water mixture) because the time...

The interface instability of the coextrusion flow of a polyethylene and a polystyrene is studied both experimentally and theoretically in a slit geometry. For prototype industrial conditions, we have found a stable/unstable transition which bounds the occurrence of stable/unstable sheets at die exit. By investigating a large range of processing...

A new coating process involving a short stretching distance (1 mm) and a high draw ratio (around 200) is considered. The resulting thin molten polymer film (around 10 micrometers) is set down on a solid primary film and then covered by another solid secondary film. In experimental studies, periodical fluctuation in the thickness of the coated...

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The stability of two-layer flow of polyethylene and polystyrene is experimentally studied in different flow geometries and for various flow rate ratios. A first coextrusion device allows to stop the coextrusion flow in a very long slit channel, to cool down the polymer sample and to dismantle the die in order to extract extrudate which is then...

Despite the fast growth of co-extruded film production, little research work has been devoted to this process. Films of LDPE, ULDPE, LDPE/ULDPE and ULDPE/LDPE were produced at various processing conditions. A continuous experimental set up was used to evaluate the in-plane birefringence during bubble formation. The data collected were used to...

The interface instability of the coextrusion flow of a polyethylene and a polystyrene is experimentally studied with industrial and laboratory equipments for various flow rates and temperature. Stable and unstable coextrusion conditions are identified as a function of flow rate ratio, shear rate and temperature. It is found that temperature and...

International audience

The polymer cast film process consists of stretching a molten polymer film between a flat die and a drawing roll. Drawing instabilities are often encountered and represent a drastic limitation to the process. Newtonian fluid film stretching stability is investigated using two numerical strategies. The first one is a 'tracking' method, which...

The polymer coextrusion process is a new method of sheet metal lining. It allows to substitute lacquers for steel protection in food packaging industry. The coextrusion process may exhibit flow instabilities at the interface between the two polymer layers. The objective of this study is to check the influence of processing and rheology...

La fabrication d'un film multicouche peut être réalisée de manière économique par l'utilisation de la technique de coextrusion. Des instabilités peuvent apparaître à l'interface entre les deux polymères ce qui rend le produit inexploitable. L'objectif de cette étude est d'étudier numériquement l'influence du procédé et des paramètres...

A key problem in the modeling of polyurethane foaming is the determination of relevant physical parameters for the viscosity, the gas expansion and the curing rate. Indeed, it is difficult to measure the chemical kinetics parameters as well as the viscosity of industrial polyurethane formulations (polyol-isocyanate-water mixture) because the...

A key problem in the modeling of polyurethane foaming is the determination of relevant physical parameters for the viscosity, the gas expansion and the curing rate. Indeed, it is difficult to measure the chemical kinetics parameters as well as the viscosity of industrial polyurethane formulations (polyol-isocyanate-water mixture) because ...

International audience

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The knife-over-roll coating process of plastisol formulations for flooring applications has been investigated. The coexistence of smooth spherical PVC particles and rough calcium carbonate aggregates in a Newtonian plasticizer makes this suspension a more complex system than those encountered in the literature. The shear viscosity has been...