Re-Examination of the Effect of the Stretch/Orientation-Induced Reduction of Friction under Equi-Biaxial Elongational Flow via Primitive Chain Network Simulation Using Two Definitions of Orientation Anisotropy

抄録

In this study, we examined the effect of the stretch/orientation-induced reduction of friction (SORF) between under uniaxial and equi-biaxial elongational flows using the primitive chain network (PCN) simulation with two definitions of orientation anisotropy under equi-biaxial elongational flow. We used two types of the orientation parameter S (S₁ and S_1/2) under equi-biaxial elongational flow, giving rise to different values 1 and 1/2 of S, as the limiting values for S₁ and S_1/2 along the elongational direction, respectively. We calculated the steady-state elongational viscosity of monodisperse polystyrene melts to observe the SORF, which should be effected at large strain rate by PCN simulation. Furthermore, we attempted molecular level analysis utilizing decoupling approximation. The difference between S₁ and S_1/2 was the critical strain rate of the SORF effect when using S_1/2. The friction decreased at the critical strain rate, which was comparable with the inverse of the Rouse relaxation time under uniaxial and equi-biaxial elongational viscosities. On the other hand, the friction under equi-biaxial elongational flow using S₁ decreased at earlier than that.