FOAMING POLYMERS WITH SUPERCRITICAL CO2 : IMPACT OF RHEOLOGICAL PROPERTIES ON DYNAMICS OF FOAMING PROCESS
Research context :
Polymer foams are porous solid materials that are heavily used in many industrial sectors (sport, packaging,
building, automotive, aerospace, ...) owning to their low weight and other functional properties (high
mechanical performance, high heat/sound insulation, ...). In particular, foaming polymer with supercritical CO2
(scCO2) is a vibrant and ongoing research field, since scCO2 is a ‘green’ and cheap solvent with mild
supercritical conditions. Using scCO2 renders foaming processes more ecofriendly, by reducing the carbon
imprint and improving the recyclability of their end products.
The rule of thumb for a ‘desirable’ polymer foams – having low cell size, high cell density, and high expansion
ratio – are difficult to attain. One reason behind this difficulty is interference of the multiple mechanisms in
foaming process, e.g. CO2 sorption causing plasticization-swelling effect, diffusion of CO2 during gas saturation
and cell growth, and local stress caused by growing CO2 pores; all of them depend strongly on the rheology of
polymer under supercritical conditions. Hence, a clear understanding of rheological properties of polymer
during foaming play a crucial role in predicting foamability and quality of polymer foams.
Project description :
As a first PhD within the framework of the ‘Chaire de Professeur Junior’ project MATPRODEFI, this thesis aims
to understand the effect of scCO2 and related parameters on macro-to-microscopic characteristics of typical
polymers, like PMMA, during and after foaming process.
The candidate will be in charge of the following experimental approaches :
- Develop new device to quantify the sorption of CO2 in supercritical state into polymer (melt/solid) as a function of saturation pressure/temperature/duration and of sample size, and to estimate the swelling and the coefficient of diffusion of polymer-CO2 system ;
- Characterize the effects of CO2 sorption on extensional rheology and viscoelasticity of polymer;
- Visualize the pore distribution/growth present in polymer-CO2 system and analyze their dynamics, by imaging or light scattering techniques.
The final goal is to provide precise experimental data about the properties of polymer-CO2 system during manufacturing, in order to model the relation between composition, rheology at multiple scales, and microstructure of polymer foam. This work will lead to a direct optimization of foaming process in industrial
setting.
Expected profile :
The candidate must be highly motivated by experimental work and instrument development, and have a
background in Physical-Chemistry or Polymer Science at Master/Engineer (or equivalent) level.
Prior experiences in Image acquisition and processing techniques are beneficial but not required.
Excellent communication skills are desirable.
How to apply :
Please send your application (CV, cover letter, and references) to Anh Vu Nguyen Le, Yvan Chalamet, and Jean-
Charles Majesté.
Supervisors :
Anh Vu NGUYEN LE, anh.vu.nguyen.le @ univ-st-etienne.fr
Informal enquiries are welcome and should be directed to Anh Vu Nguyen Le.
Yvan CHALAMET, yvan.chalamet @ univ-st-etienne.fr
Jean-Charles MAJESTE, jean.charles.majeste @ univ-st-etienne.fr
Laboratory :
Ingénierie des Matériaux Polymères (IMP, UMR CNRS 5223), Saint-Etienne, France
Contract :
3 years, fully-funded (~25 k€/year in gross salary)
Starting date :
Fall 2023 (no later than November 2023)
Deadline :
30th May 2023
Model and Robust Greener soft Colloids : Tunable materials for advancing polymer science and new applicationsOffre de thèse
Research project :
In the rich landscape of soft colloids, fundamental understanding required to synthetize well defined “model” systems that are homogenous at different scales. For microgel, a free-defect structure corresponds to a homogenous crosslink density, without “loop” and free dandling
chain, and a narrow distribution in size. In industrial application, costs, performance and straightforward production lead to complex soft colloid systems with heterogeneous size and microstructure. Their different architectures offer many possibilities to tailor flow properties and performance of the complex
fluid. This balance between heterogeneity and homogeneity is also observed in other scientific field, like in biology for plant classification. In colloid science, we can associate to the balance between heterogeneity and homogeneity the concept of model and robust system.
Within the framework of the ANR project MrGreco, the objective of this PhD project is to design “Model” and “robust” Greener soft colloids, to investigate the impact of their homogeneous/heterogeneous internal structures on properties. To achieve this objective, the greener soft colloids will be fashioned from a bio-based polymer, the chitosan. Comparison between “Model” and “robust” greener soft colloids will be discussed in term of fundamental approach, performances and biodegradability, to finally explore specific applications, such as the 3D printing of bio-inks and the formulation for hair care cosmetics.
This project will be integrated within the laboratory IMP (UMR CNRS 5223) between Saint-Etienne (Université Jean Monnet, main location), and Lyon (Université Claude Bernard Lyon 1). The IMP team is renowned for his research activities in polymer science, with important facilities. Its main research aim is to establish and to control relationships between chemistry, structure, rheology and processing.
Candidate profile :
Highly motivated students with a Master/Ingénieur degree, or equivalent, in the field of polymer science (chemistry and physical-chemistry) are encouraged to apply. A prior knowledge on process (twin-screw extruders), rheology and scattering techniques will be also appreciate. Excellent writing and oral communication skills.
Application :
Send to the contact below your CV, cover letter, grades and qualification (achieved and/or expected), and two references for recommendation letter.
Deadline for application : 20th April 2023.
Duration : 36-months contract, from September 2023.
Location : France, Saint-Etienne, with regular secondment at Lyon.
Contacts : Dr. Fabien Dutertre, IMP (fabien.dutertre @ univ-st-etienne.fr).
