Rheological behavior of POM polymer melt flowing through micro-channels

Determination of the rheological behavior of the polymer melt within micro-structured geometry is vital for accurate simulation modeling of micro-molding. The lack of commercial equipment is one of main hurdles in the investigation of micro-melt rheology. In this study, a melt viscosity measurement system for POM melt flowing through micro-channels was established. For measured pressure drop and volumetric flow rate, both capillary and slit flow models were used for the calculation of viscosity. The calculated results were also compared with those of PS resin to discuss the effect of morphology structure on the viscosity characteristics of polymer within micro-channels. It was found that the measured POM viscosity values in the test ranges are significantly lower (about 29-35% for a channel size of 150 μm) than those obtained with a traditional capillary rheometer. Meanwhile, the percentage reduction in the viscosity value and the ratio of slip velocity relative to mean velocity all increase with decreasing micro-channel size, but less significantly when compared with PS resin. In the present study we emphasize that the rheological behavior of the POM resin in microscopic scale is also different from that of macroscopic scale as PS resin but displays a less significant lower. It also revealed that the wall slip occurs more easily for the PS resin within micro-channels than POM resin due to enlarge the effect of molecular weight.