The Laboratory 3SR is looking for a pos-doc researcher as part of the European project Celluwiz, to work on the wet lamination and drying of cellulose nanofibrils hygrogels on paper boards for renewable and biodegradable packaging: microstructures and hygromechanical couplings.
The objective of Celluwiz is to produce multilayered biobased structures made of paper boards onto which cellulose nanofibrils (CNF) films are deposited via the wet lamination process. These new bio-based fibrous materials exhibit valuable specific mechanical properties and excellent permeability to gases and even to water (if CNF films are properly treated, e.g., with chromatogeny). However, during the wet lamination, many complex mechanisms occur such as the high anisotropic shrinkage of the CNF hydrgogels during their drying, as well as their adhesion to the paper board substrates. These mechanisms are not well understdood and induce important defects on the produced materials: development of internal stresses and high residual strains leading to undesirable curling (see figure), clocking and delamination phenomena.
The main objective to the postdoc is to characterize these defects, by investigating the hygro-mechanical behaviors of (i) the CNF hydrogels during their drying, (ii) the paper boards, (iii) the multilayered systems.
For that purpose, various experimental analyses will be carried out:
- Mechanical tests with various mechanical loadings (uniaxial, plane strain and bi-axial tensions), controlled environment (temperature, relative humidity) and kinematical field measurements (SDIC),
- 3D imaging using laboratory (3SR Lab) and synchrotron (ESRF) X-ray micro tomography for multiscale 3D in situ observations of drying phenomena for the CNF hydrogels and the multi-layered systems.
The post-doc fellowship is for 18 months starting from March 2020 and will be located at the Laboratory 3SR.