Study On Mixing Properties Of Rotating Mixer In RIM

The Kenics rotary system mixer is a kind of new highly effective mixer, its mixing performance goes far beyond the Kenics static state mixer. In recent years it is widely used in the low pressure reaction injection molding. But the structure on its mixing performances is not studied thoroughly. The Kenics element leads to high equipment investment and the run cost in the use process.Based on the Kenics rotary system, two more simply elements are proposed. One is named as interrupted-screw element, another is plane-plate element. Using the FLUENT finite element software simulates the mixing of interrupted-screw element, the Kenics element and plane-plate element, which have the natural size (considering sleeve and mixer gap). It turns out that average strain rate and mixing efficiency increase with throughput, rotating speed, element numbers, but decrease with gap and long diameter ratio. At same conditions, the screw element can achieve highest mixing efficiency.By the experiments on mixing performance, three kinds of rotating mixing elements used for RIM are studied from two aspects of product quality and reaction of temperature field. It turns out that interrupted-screw element can establish the biggest injection pressure, product quality is the best, the Kenics element is better than plane-plate element. The screw element can achieve same mixing efficiency as the Kenics element, which made two material mixing intensively, react fiercely, solidify the velocity quickly. While the slowly reaction and long time need to solidify are the characteristics for using crossing plane-plate element. That is to say, compare to cross structure, screwy structure plays primary role for rotating mixing in RIM.The paper also studies the influence of primary structure parameter to the effect of Kenics rotary system mixer. By simulating average strain rate and section density of tracing granule, using high speed photograph to record flowing mixing ,it tests two aspects from the theory to analyze long diameter ratio and the angle of torsion to the Kenics rotary system mixer mixing effect influence, mixing efficiency increases with the angle of torsion, but decreases with long diameter ratio.Finally, the paper studies the pressure drop of interrupted-screw element and the Kenics element under the different operating condition and primary structure parameter. The pressure drop of two kind of elements increase with throughput and rotating speed .In high rotating speed, it has gentler change and small scope grows; it aslo increases with angle of torsion, decreases with the long diameter ratio.