双螺杆挤出过程中分散质量的动态研究

Study on Dynamic Mixing Quality During Twin-screw Extrusion

对双螺杆挤出过程计量段PP／炭黑混合物的分散质量进行了动态研究。采取在线取样的方式取样，并将样品压制成薄片，进行显微照相，通过分析图像量化了物料的分散质量。探讨了螺杆转速对挤出机计量段PP／炭黑混合物分散质量的影响。结果表明，对于单一形式的螺杆构型，在螺杆转速为40～240r／min的范围内，随着螺杆转速的增加，计量段处PP／炭黑混合物的分散质量呈下降趋势；螺杆转速为80～120r／min时，计量段处PP／炭黑混合物的分散质量相对于40r／min下降程度较大。螺杆转速影响着PP／炭黑混合物在挤出机内停留时间和流变性质，两者的共同作用是产生这一变化的原因。

An empirical method using a ＂transparent＂ extruder was developed to study the dynamic mixing characteristics of twin-screw extrusion. The specimens collected from the metering section of the extruder during the process were pressed into flakes which were then photographically captured under a microscope for subsequent staffstically analysis （largely variance）. The analysis was made on the measurement of the pixeI intensity of the digitized films which enabled quantification of mixing quality possible. The focus of this investigation was on the effects of screw speed. For the selected single-flighted conventional screw, it was found that when the screw speed was in the range of 40 - 240 r/min, the higher the screw speed, the poorer mixing quality. The results suggested that a criti- cal screw speed for optimized mixing might have been present. For the equipment used in the current project, this critical screw speed lied between 80- 120 rpm.