This paper sums the study results on wall slip of polymer melt in shear flow

which leads to the physical meaning of the developed Z-W model. In the model

it was realized that there was interfacial layer at the wall

real wall slip occurred at the wall interface through adsorbing-desorbing; apparent slip occurred in interfacial layer through disentanglement-reentanglement. On the other hand

the interfacial molecules were confined with different dynamics with that of internal melt; there is elastic tension between bulk chains and interfacial ones. Z-W model reduces to one second order differential equation in simple shear flow. This model first quantitatively shows general wall slip contains adhesive slip and cohesive slip as well as elastic deformation slip. The self-oscillation in capillary extrusion was reviewed. It was frist time to propose the definitions of multiple internal self-oscillation and multiple external self-oscillation. The simplified Z-W model qualitativedly explained such nonlinear flow phenomena as the non-linearity of shear stress

the transient self-oscillation in pressure

the stick-slip transtition and sharkskin features in capillary rheometry. The Z-W model was reduced to a

Duffing

equation to show linearity in small amplitude oscillatory shear and complex nonlinearity at large amplitude. The complexity changes with viscoelaticty of polymer melt and vibration amplitude or frequency. The Z-W model also reduces to the published Josh'is model

dynamical network model or the model by Hatzikirizkos and the model by Graham under special conditions. In all

Z-W model was abundant in usage with certain rationality.