Preliminary study of polymer melt rheological behavior flowing through micro-channels

Determination of melt rheological behavior within micro-structured geometry is very important for the accurate simulation modeling of micro-molding. Yet investigation of micro-melt rheology is difficult due to the lack of commercial equipment. In this study, melt viscosity measurement system for polymer melt flowing through micro-channel was established using a micro-channel mold operated at a mold temperature as high as the melt temperature. Form measured pressures and volumetric flow rate both capillary flow model and slit flow model were used for the calculation of viscosity utilizing Rabinowitsch and Walters corrections. It was found that the measured viscosity values in the test ranges are significantly lower (about 30% to 80% lower) than those obtained from traditional capillary rheometer no matter what capillary flow model or slit model are used for analysis. As micro-channel size decreases, the percentage reduction in viscosity also increases. This indicates microscopic scale melt rheological behavior is different from that of macroscopic scale and that current simulation packages are not suitable for micro-molding simulation without considering this difference.