화학공학소재연구정보센터
Journal of Rheology, Vol.45, No.3, 627-639, 2001
Application of large double-step shear strains to analyze deformation and shape recovery of a polymer droplet in an immiscible polymer matrix
The deformation and shape recovery of a soft polymer droplet in an immiscible polymer matrix with higher viscosity were directly observed from two directions after application of large double-step shear strains. After application of the first-step strain gamma (1) (\ gamma (1)\ = 5), the deformed droplet changes its shape, starting from a Rat ellipsoid to a rodlike shape then to a dumbbell, an ellipsoid of revolution, and finally back to a sphere. When a large second-step strain gamma (2) is applied in the same or opposite direction to the first strain during the recovery, the shape of the droplet and the orientation angle depend on both gamma (2) and the shape during the recovery. Just after application of gamma (2)(0 < gamma (2) less than or equal to5) in the opposite direction to the first strain gamma (1)( = -5), the droplet having a rod-like or dumbbell shape significantly deforms at both ends and stretches more than expected from the assumption of affine deformation. Tile deformed droplet under strain gamma (2) has two orientation angles, theta (1) and theta (2), to the shear direction. The main angle theta (1) of the inclined droplet is equal to the angle given by the total strain gamma (1) + gamma (2), i.e., cot 2 theta (1) = (gamma (1) + gamma (2))/2. On the other hand, another angle theta (2) observed at both ends of the deformed droplet. is close to the angle given only by gamma (2), i.e., cot 2 theta (2) = gamma (2)/2. This difference in the orientation angle suggests a faster recovery at both ends and a slower recovery (remaining effects of the first strain) in the central part.