Rheology is science which treats the deformation and flow of materials. The science of
rheology is applied to the physics, chemistry, engineering, medicine, dentistry, pharmacy,
biology and so on. Classical theory of elasticity treats the elastic solid which is accordant to
Hooke’s law [1]. The stress is directly proportional to strain in deformations and is not
dependent of the rate of strain. On the other hand, that of hydrodynamics treats the viscous
liquid which is accordant to Newton’s law [1]. The stress is directly proportional to rate of
strain and is not dependent of the strain. However, most of materials have both of elasticity
and viscosity, that is, viscoelastic properties. Mainly viscoelastic properties of the polymers are
analyzed in rheology. Rheology would have two purposes scientifically. One is to determine
relationship among deformation, stress and time, and the other is to determine structure of
molecule and relationship between viscoelastic properties and structure of the materials.