Soutenance de thèse : Robins KUMAR

Multi-scale structuration and dynamic mechanical response of multi-phasic elastomer systems

Doctorant :  Robins KUMAR

Laboratoire INSA : MATEIS

Ecole doctorale : ED034 Matériaux de Lyon

In this study, new types of elastomer systems - seen as an alternative for conventional nanocomposites widely used in tire industry - were prepared and investigated  thoroughly. They are made of an SBR (Styrene-Butadiene Rubber) matrix, blended with one resin among three resins with low molecular weight resins, with a higher Tg than the polymer, and different miscibilities. Such materials raise different questions: How does the resin incorporation influence the elastomer network structure? Depending on the miscibility and the resin content, what is the resulting morphology? How does the morphology evolve with the temperature, the processing conditions and the crosslinking protocol? And of course, how this morphology impacts the macroscopic mechanical properties?
Two of the studied resins showed good miscibility, with the absence of phase separation, and no strong influence on the chemical crosslinking reactions of the polymer. Their impact on the viscoelastic behavior is the consequence (i) of a modification of the polymer glass transition, which is broadened due to the presence of resin concentration fluctuations, and shifted towards higher temperature, and (ii) of the dilution of the polymer during its crosslinking, which results in a decrease of the modulus above the glass transition temperature. The third resin has a lower miscibility. In addition to a modification of the glass transition and to a dilution effect, it leads to a phase separation, and therefore the existence of a resin rich phase. This phase is rigid at ambient temperature and reinforces the polymer rich phase, i.e the elastomer matrix. Interestingly, this phase separation slightly depends on the temperature, with a kinetics which may provide a new way to pilot the viscoelastic response of the material.
Key-words: Elastomer, Polymer/resin blends, phase separation, dynamic mechanical analysis.