ABSTRACT
The spurt phenomenon for nearly monodisperse, high-molecular-weight, polymer melts and concentrated solutions is of critical importance to the plastics processing industry. These melts and solutions exhibit an abrupt increase in flow rate when the wall shear stress exceeds a critical value in pressure driven shear flow. Up to the present, melts and solutions have been modeled by differential constitutive equations for the “extra stress” tensor. This chapter investigates single history integral equation constitutive models as an alternative for modeling spurt. It shows how to obtain asymptotics, demonstrating that the four dynamic phases of supercritical startup of pressure driven shear flow are ubiquitous. The chapter shows that the dynamic features for the spurt phenomenon predicted by the single integral constitutive equations are the same as those predicted by differential constitutive equations. This suggests that the differential models do capture the essential underlying molecular physics heretofore solely attributed to the single integral models.
