In-line steady shear flow characteristics of polymer melt in rectangular slit cavities during thin-wall/micro injection molding

Abstract

Both scale and temperature field effects have a considerable impact on polymer melt viscosity during thin-wall/micro injection molding. In this work, an in-line rheological test with similar dynamic test conditions to thin-wall/micro injection molding was adopted to further analyze the rheological properties and improve the simulation accuracy. An injection mold with rectangular slit cavity and storage region was designed to obtain a steady flow. The effects of factors such as the cavity size, viscous dissipation and melt temperature on polymer melt viscosity were studied. The results demonstrate that the injection molding conditions have a significant influence on the in-line rheological properties. When the cavity thickness (h) was 0.5 mm, the average percentage reductions of viscosity were 8.86 % (200 to 220 °C) and 4.07 % (220 to 240 °C) as the melt temperature rose. They were 57.13 % (200 to 220 °C) and 38.86 % (220 to 240 °C) when the cavity thickness was reduced to 0.2 mm. The test results show that the average prediction errors of pressure drop based on the capillary rheometer viscosity and in-line viscosity are 29.78 % (die: 5/0.2 mm) and 16.61 % (slit:h = 0.2 mm), respectively. In-line rheological viscosity shows potential for application in mold flow simulation.

Keywords

• In-line metrology
• Thin-wall/micro injection molding
• Steady flow
• Shear viscosity
• Non-isothermal effect