Morphology development under shear flow of a cross-linked dispersed phase
philippe Cassagnau, Yves Deyrail
Laboratoire des Matériaux Polymères et Biomatériaux
France

Keywords: morphology , cross-linking, optical shear device

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Deformation under shear of a dispersed polyethylene-vinyl acetate copolymer (EVA) phase in a polystyrene matrix or PDMS matrix was investigated using a hot optical shear device. First , deformation of EVA droplets and its modeling at isothermal temperatures was studied for comprehension purpose. Overall agreement with literature models was found and main influence of the viscosity ratio was brought to the fore. Second, morphology control through cross-linking of the EVA dispersed phase was experimented. It consists in one hand to deform a cross-linked phase (nodules or fibrils) at different extents of cross-linking and on the other hand to cross-link the dispersed phase under shear flow. Deformation and break-up times of EVA fibers were taken into account. Dependence of shear rate and extent of cross-linking on final morphology was demonstrated. The deformation of a cross-linked nodules depends on the cross-link network density. Furthermore, during the dynamic cross-linking, rapid cross-linking reaction enables stable fibrillar morphology. Long cross-linking reactions allow nodular morphology, whose size depends on the shear rate used