Abstract: For two-phase polymer blending systems, the development of theoretical models on the deformation of Newtonian(or viscoelastical)droplet suspended in another Newtonian(viscoelastical)medium is discussed. The dominating factors which influence the droplet deformation include composition, viscosity and elasticity ratios, dynamic interfacial tension, critical capillary number, and flow field type and its intensity. For the systems in which both of the two phases are Newtonian liquids, the theoretical prediction...