Rheological Properties And Their Coupling Effects In Micro Extrusion Process

Lightweight and precision have gradually become important standards to measure the quality of industrial products.In micro extrusion process,the rheological properties of polymer melt are affected by velocity,pressure and temperature.At the macro scale,some rheological properties have little effect on the melt flow behavior.At the micro scale,due to the decrease of channel characteristic size and the increase of melt surface area and volume ratio,the influence of these rheological properties on melt flow behavior cannot be ignored.Different rheological properties have the same influence factors,so different rheological properties will influence each other through the same influence factors,that is,there are coupling effects.In this paper,the rheological properties and their coupling effects of polymer micro extrusion in several typical cross-section channels are studied.(1)The rheological properties and their coupling effects of polymer micro extrusion in circular cross-section channel are studied.The shear viscosity model and viscous dissipation model considering wall slip are established at micro scale,the distributions of velocity and pressure considering wall slip are calculated,and the effects of velocity and pressure on shear viscosity and viscous dissipation are analyzed.It is found that the responses of shear viscosity and viscous dissipation to velocity and pressure change significantly due to wall slip,the specific performance are as follows: With the increase of wall slip,the response of shear viscosity to velocity increases,the response of shear viscosity to pressure increases,the response of viscous dissipation to velocity decreases,the response of viscous dissipation to pressure decreases.The shear viscosity model considering viscous dissipation is established at micro scale,the coupled model of viscous dissipation and convective heat transfer is established,and the temperature distribution of polymer melt considering viscous dissipation is calculated.The influence of temperature on shear viscosity is analyzed,the coupling effect of viscous dissipation and convective heat transfer is analyzed.It is found that the change trend of response of shear viscosity to temperature of melt considering viscous dissipation is more obvious than that without considering viscous dissipation,however,the shear viscosity of melt considering viscous dissipation is lower;The coupling effect of viscous dissipation and convective heat transfer is as follows: Viscous dissipation enhances convective heat transfer through temperature,while convective heat transfer weakens viscous dissipation through temperature.(2)The rheological properties and their coupling effects of polymer micro extrusion in slit die are studied.The similarities and differences between the coupling effects of slit die micro extrusion and circular cross-section channel micro extrusion are analyzed.It is considered that the inlet pressure of channel plays an important role in coupling effects of rheological properties.The higher the inlet pressure,the stronger the coupling effects.On the contrast,the weaker the coupling effects are.(3)The micro extrusion of polymer in annular cross-section channel and co-extrusion of double polymer in circular cross-section channel and their rheological properties are studied.The distributions of velocity and pressure considering wall slip are analyzed,and the shear viscosity models and viscous dissipation models considering wall slip are established;The temperature distributions considering viscous dissipation are analyzed,and the viscous dissipation models considering coupling effect are established.