Abstract: For viscous dissipation effect of the polymer melts flowing in micro-scale channel on their flow performance. The micro-injection molding experimental system with temperature sensors and ultrasonic field are designed. The temperature rises at the outlet of the rectangular cross-section micro-channel caused by viscous dissipation at different process parameters and ultrasonic power changes are investigated, using polypropylene(PP) and high-density polyethylene(HDPE) two polymer melts by the single factor molding experiments. The results show that the viscous dissipation effect of the polymer melts flowing in micro-scale channels is enhanced with the increase of injection rate, while it can be weakened by the rise of inlet melts temperature and mold temperature and the outlet temperature rise of the two materials with ultrasonic vibration can be significantly higher than that without ultrasonic vibration. However, their temperature increases vary greatly for microscopic molecular structures of different materials and their thermo-physical properties. PP melt temperature increase applying ultrasonic vibration is 34.7% higher than that without ultrasonic vibration at the set injection speed, while it is 71.7% for HDPE. But the under a certain ultrasonic frequency and process parameter，increasing the ultrasonic power make PP melt temperature increase by 24.8%, while it is 83.6% for HDPE. It’s obvious that the viscous dissipation effects of polymer melts flowing the micro channel can be enhanced by applying ultrasonic field.

Key words: experimental measurement, micro-scale channel, polymer melts, ultrasonic field, viscous dissipation