SYNOPSISThe transesterification reaction in the molten state of ester groups of ethylene vinyl acetate (EVA) copolymers and ethylene acrylic ester (EMA) copolymers has been used to crosslink the chains of this polymeric system. The relative EVA copolymers (or EMA copolymers) concentration dependence of the network formation by co-crosslinking of EVA/EMA miscible blends has been assessed. EVA/EMA networks were characterized by swelling experiments, rheological measurements, and determination of the extent of the reaction through a chromatographic technique. All results can be compared in a master curve. The influence of the polydispersity and the microstructure of EVA and EMA samples was put in evidence. On the other hand, a scaling law ( u Z -M , -~'~) was observed in agreement with predictions of the Flory-Rhener expression.
SYNPOSISThermorheological properties of an incompatible polymer blend of polypropylene inclusions dispersed in a ethylene copolymer matrix were discussed from the emulsion model developed by Palierne. Due to the different rheological behaviors with temperature of the two phases, such a system proved to be a judicious blend in order to consider the special cases of the model applications: (1) the two phases are viscoelastic liquids, (2) the dispersed phase is a solid elastic assimilated to rigid spheres in comparison with viscoelastic liquid behavior of the matrix, and ( 3 ) the two phases are elastic solids. At low frequencies, the rheological behavior of the blend was not correctly predicted by the model. So interactions other than hydrodynamics can exist in the intrafacial region, and physical entanglements between the chains of the two constituents leading to topological interactions may be assumed at the interphase. 0 1995 John Wiley & Sons, Inc.
I NTRO DUCT10 NMechanical measurements are known to be very useful for the characterization of incompatible polymer blends. The rheological behavior of polymer blends is generally complex, particulary in the case of immiscible blends where the rheological properties depend strongly on composition and viscoelastic properties of the constituents. The linear viscoelastic behavior of incompatible polymer blends has been extensively treated in the literature from experimental and theoretical points of view. One of these models, which has been commonly used in recent publications, is Palierne's model. Starting from the concepts of emulsion rheology, Palierne' studied the linear viscoelastic behavior of a dispersion of incompressible viscoelastic materials with interfacial tension. A linear viscoelastic modulus at any concentration and polydispersity of spherical inclusions was derived. The resulting expression of the average modulus includes several results of the literature as special cases: the Kerner2 formula for blends of incompressible elastic materials, and Dickie's model3
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