Material Science

The incorporation of mineral particles into an elastomer in order to obtain a homogeneous composite material requires a lot of energy. Moreover, the homogeneity of the mixture at a mesoscopic scale, a feature that controls the mechanical properties of the composite material, is not guaranteed. This issue is of course crucial during the fabrication of the main component of tires. A homogeneous mixture can be obtained at the colloidal scale by working in aqueous phase. We have recently demonstrated that the control of the sol-gel transition at the colloidal scale of a suspension of natural rubber, an elastomer which is extracted from Hevea trees in the form of emulsion droplets (latex), and carbon black can lead to a homogeneous composite material. One of the major fundamental questions to be addressed is to understand the origin of the high reactivity between the two classes of particles and thus the underlying interactions that are involved in this remarkable irreversible heteroaggreation.

Industrial partnership: Michelin

We have developed a process for making liquid core capsules having a thin hydrogel membrane. The capsules result from the gelling of an alginate solution that encapsulates a liquid drop (oils or aqueous solutions) formed by the coextrusion of the various liquid phases. For instance, these capsules can be used for encapsulating actives in cosmetics or act as bioreactors for cell culture. We are investigating the diffusion of molecules through the hydrogel membrane as well as its mechanical properties. Moreover, we are able to add an intermediate liquid or solid layer between the core and the shell that allow de modify their permeability.

Industrial partnership: Capsum

The stabilization of emulsion drops having a millimeter size is extremely difficult to achieve. This observation principally results from a large contact area between drops that favors coalescence. Moreover, creaming or sedimentation of drips under gravity are enhanced. In the Lab, we are developing fabrication processes of such emulsions by stabilizing the interfaces with a thin layer of polymers. We are investigating the stability properties of these drops  towards coalescence and breakup. Moreover, this material offers an aesthetic that should lead to new visuals and applications in cosmetics and fragrance domains.

Industrial partnership : Capsum