Nadine Allanic

Temperature mapping in a two-phase water-steam horizontal flow

ABSTRACT This experimental study focuses on the investigation of a flow boiling that occurs during the cooling process of a high temperature heated horizontal channel. Unpressurized water is used as working fluid. An intrusive thermally instrumented cell enables the phase change to be detected at different positions inside the channel. Alongside, welded thermocouples on the external wall of the channel give information about the influence of the phase change. Several cooling flowrates are tested in order to study their influence on the phase change duration. Finally, experimental results are compared to numerical simulations to determine some characteristic parameters as bulk temperature and heat transfer coefficient.

Study of the rheological behavior of polypropylene/polyethylene extruded mixture using an instrumented die

During the recycling of polypropylene (PP), some pollutants are likely to be present in the polymer. Most of these pollutants are polyethylene (PE) which tends to form a heterogeneous blend with PP due to their incompatible nature. In the present study, PP and PE were extruded with different volume fractions of PE. The pressure drop and the temperature variation within the flow in a cylindrical die were studied. A finite element model was used in order to predict the rheological behaviors of the studied polymer mixture ratios. The results obtained in this work show that the rheological response of the blend is very sensitive to the viscosity of the minor polymer when it is lower than the viscosity of the major polymer.

Choline chloride vs choline ionic liquids for starch thermoplasticization

Native starch containing 12% water was melt processed in presence of 23% of various plasticizers at 120°C, either by simple compression molding or by extrusion using a laboratory scale microcompounder. Glycerol, a typical starch plasticizer, was used as a reference and compared to three choline salts: raw choline chloride (which is a solid in dry state with a melting point above 300°C), and two ionic liquids synthesized from this precursor (choline acetate and choline lactate, liquids below 100°C). These ionic plasticizers were shown to allow a more efficient melting of native starch in both processes. The investigation of macromolecular structure changes during processing shows that this efficiency can be ascribed to a starch chain scission mechanism, resulting in lower specific mechanical energy input need for starch thermoplasticization compared to glycerol plasticized starch. Compared to the synthesized ionic liquids, raw commercial choline chloride leads to a good compromise between limited chain scission, and final water uptake and thermomechanical properties.

Prediction of thickness distribution of thermoformed multilayer ABS/PMMA sheets

In thermoforming, one of the main difficulties is to avoid the presence of weak thickness in the most deformed zones. After the heating stage, a bubbling step, leading to a first rate of deformation, is often used. In this work, we assess how the initial bubbling deformation can be controlled in order to obtain a homogeneous final thickness of the product. Experiments are performed on a multilayer sheet product. An industrial mould, corresponding to a casing of a non-licensed car, was adapted on a lab thermoformer. After presenting experimental thermal profiles of the multilayer sheets measured during the heating stage, a first geometric model is investigated to predict the thickness distribution. Numerical results are compared with measurements.

Thermo-Kinetic Analysis of Liquid Silicone Rubber

Modeling and optimization of LSR parts require an accurate kinetic modeling of the material crosslinking. Calorimetric and mechanical measurements for different temperature ramps are used in order to calculate the crosslinking extent as a function of time and temperature. These measurements are numerically treated in order to determine the parameters of a representative model. The chosen model will be used to simulate a LSR molded parts and design a LSR controlled molding setup.