Abstract: The mechanism of micro-scale effect contributing to the change of polymer melt viscosity is proposed on the basis of the measurement principle of capillary rheometer. Based on Kelvin-Voigt constitutive equation, a mathematical model of micro-scale viscosity is built. The micro channel dies of 1 000μm, 500 μm and 355 μm diameter are developed and with several polymers, including PP, PS and HDPE, the measurement experiments of polymer melt viscosity are carried out at various shear rate. The results show that the melt viscosity reduces with the decrease of micro-channel size at the same shear rate and that the difference of viscosities in different micro channels reduces with the increase of shear rate. Test data are incorporated into the mathematical model for theoretical calculation. Results show that theoretical curves are consistent with experimental curves and the maximum difference is less than 8%, which verifies the rationality of the mathematical model. This finding provides the theoretical and experimental references for accurate simulation of filling flow and design of micro mold in micro injection molding and micro extrusion.

Key words: Micro channel, Micro injection molding, Micro-scale effect, Micro-scale viscosity model, Micro-scale viscosity test, Polymer melt