Characterization Formula for Shear Stress of Polymer Melt Dynamic Extruding through Capillary

Abstract

The mathematical model for the shear stress in a polymer melt within a capillary was set up by superimposing a sine vibration of small amplitude in parallel with the extruding direction of the polymer melt. By making use of experimental equipment of the constant velocity type dynamic rheometer of capillary (CVDRC), designed by the authors, the steps required to calculate the shear stress in the polymer melt at the inside wall of the capillary under a vibration force field were also established. By measuring the instantaneous data of capillary entry pressure, capillary volume rate and their phase-difference under a superimposed vibration, the shear stress of the polymer melt at the wall of the capillary can be calculated.

A Model for Primary Normal Stress Difference of Dynamic Extrusion of a Polymer Melt through a Capillary

“…Knowing the shear stress at the capillary wall under a preset frequency f and amplitude A of vibration [7][8][9][10] , we get DYNAMIC EXTRUSION OF A POLYMER MELT THROUGH A CAPILLARY s w ðtÞ ¼ a Á Dp Á ½1 þ e p cosðx p t þ uÞ…”

“…The Constant Velocity Dynamic Capillary Rheometer superimposes a sinusoidal displacement vibration in parallel on the extruded direction of polymer melt through the capillary [7][8][9][10] . Assume that the length of capillary is L, the radius R, and the length of the entire development region L In this study, for convenience sake.…”

“…This was done by taking a polymer melt that flows through a capillary under a superimposed vibration as the studied object, and using a Constant Velocity Dynamic Capillary Rheometer, which was designed by the authors [7][8][9][10] .…”

Study on Self-Reinforcement of High-Density Polyethylene Extruded with Vibration in Low Temperature

“…Thus the vibration effect is very limited because the polymer vibration just presented in a local section; on the other hand, it is difficult to extend to practical manufacture because each kind of the die for producing products needs specialized design. In contrast, in an electromagnetic dynamic plasticating extruder (EMDP) for plastics, invented by Qu [5][6][7][8], there is a reciprocating vibration force field introduced into the whole plasticating and extrusion process, including solid transfer, melting and melt flow, resulting in positive effects on the material transportation and plasticizing. Because of the vibration of the screw, an additional stress is added to the shear flow of the polymer melt.…”

“…As a result, the inner microstructure of the products is also changed during forming and solidifying of the extrudate, which could greatly enhance product properties [5]. It had been verified that the EMPD had multiple advantages over traditional extruder, such as low energy consumption, high output, low melt die swell ratio, and superior mechanical and surface quality of the extruded products [6][7][8]. There are also investigations have been done on its effect on the relationship between microstructures and properties by Qin et al [9][10].…”