Analysis of the total rheological model of the polymer melt flow
Keywords:non-Newtonian fluid, rheology, flow model, relaxation, polymer melt, viscosity, flow rate, "sharkskin"
Plastics processing is regulated by the shear strain rate, so developing the flow models in a wide range of shear rates is an urgent task.
A comparative analysis of the total rheological curves of the polymer melt flows using two flow models was performed. The Levanichev "slug" flow model is based on a physical model and assumes that the non-Newtonian flow area occurs when the melt flow rate approximates to the relaxation rate. The Carreau model is semi-empirical, viscosity limit values and relaxation time are taken into account, non-Newtonian flow area is described by the flow index.
As a result of the analysis, the viscosity prediction errors were identified, and advantages of the "slug" flow model were shown. The method for calculating the flow of non-Newtonian fluid, where viscosity is understood as a change in the interaction area, resistance to the melt compression and overcoming melt adhesion to the channel walls was given, a new viscosity dimension was proposed.
A number of effects that arise during the plastics processing and engineering methods based on the physical model, describing the total rheological curve ("sharkskin", "diedroop", "discopurgeprocedure") was qualitatively considered.
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