Polymers sheared morphologies

Rusu D (1997) In-situ study of immiscible polymer blends morphology under simple shear PhD thesis Ecole des Mines de Paris, Sophia Antipolis... 

Drop deformation and breakup plays a decisive role in the evolution of polymer blend morphology. The breakup mechanism during polymer blending is very complex and is influenced by many variables, such as shear stress, viscosity ratio, stress ratio, Deborah numbo-and first normal force difference [1-3]. Visualization was used to get realtime information during the drop deformation and breakup process [1-5]. It is shown that drops can break up in simple shear flow via different modes such as breakup in the flow axis, erosion, parallel breakup, tip streaming and breakup along the vorticity axis [1-7]. 

In manufacturing and processing polymer blends, it is thus important that the viscosity ratio be within the optimal range in the actual processing conditions. Not only the polymers to be blended but also the temperature and processing conditions (shear, elongation) should be carefully selected. Other factors, such as interfacial tension [46,47] and elasticity of the blended polymers, may also influence the blend morphology. 

Rotations around torsional barriers induce changes in chain conformation. For conjugated systems like polydiacetylenes, flow-induced changes in chain conformation can have a profound influence on the photon absorption and electronic conductivity properties of the material [73]. Flow-induced changes in molecular conformation form the basis for several technically important processes, the best known examples are the production of oriented fibers by gel spinning [74], the compatibility enhancement [75] and the shear-induced modification of polymer morphology [76]. 

By special processes, like polymerization under shear conditions or flash-spinning of polymer solutions, it is furthermore possible to obtain materials which do not only have this new shish-kebab micro-morphology, but also a new macro-morphology, namely the polymer fibrids.35... 

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