Abstract
The fluidity of a molten polymer plasticized by ultrasonic vibration was characterized by spiral flow testing based on an Archimedes spiral mold with microchannels. Mold inserts with various channel depths from 250 to 750 µm were designed and fabricated to represent the size effect under micro-scale. The effect of ultrasonic plasticizing parameters and the mold temperature on the flow length was studied to determine the rheological nature of polymers and control parameters. The results showed that the flow length decreased with reduced channel depth due to the size effect. By increasing ultrasonic amplitude, ultrasonic action time, plasticizing pressure, and mold temperature, the flow length could be significantly increased for both the amorphous polymer polymethyl methacrylate (PMMA) and the semi-crystalline polymers polypropylene (PP) and polyamide 66 (PA66). The enhanced fluidity of the ultrasonic plasticized polymer melt could be attributed to the significantly reduced shear viscosity.
Highlights
Ultrasonic microinjection molding has become an attractive alternative molding technology for polymeric micro components
That means the ultrasonic wave with amplitude of 32 μm was enough to plasticize polymethyl methacrylate (PMMA), but not enough to plasticize PP and
The flow properties of polymer melt were investigated for ultrasonic microinjection molding, using spiral flow testing under micro-scale
Summary
Ultrasonic microinjection molding has become an attractive alternative molding technology for polymeric micro components. Instead of traditional heater band and screw pressing and shearing, high-frequency periodic mechanical vibration energy works as a plasticizing agent in ultrasonic microinjection molding [1]. This vibration-induced inside-out heat generation plasticizing is much more energy efficient than the traditional outside-in heat conduction. The plasticized molten material is further influenced by the ultrasonic agitation effect, leading to a reduced melt viscosity and enhanced cavity filling performance. Ultrasonic microinjection molding has gained extensive attention in recent years due to its great potential to reduce energy consumption, increase materials utilization, and enhance molding performance [2,3,4,5,6,7,8,9,10,11,12,13,14]. This study focused on the influence of the ultrasonic agitation effect on the plasticized molten material
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