THE EFFECT OF A NEW-TYPE OF PIN MIXING SECTION ON THE PERFORMANCE OF A SINGLE-SCREW EXTRUDER

The effect of a holed-pin mixing section on the performance of a singl e screw extruder was investigated and compared with a free flight and a normal pin mixing section, using a practical single-screw extruder. The effect of axial distance between two pins in a holed-pin mixing se ction on performance was also studied. Mixing ability was quantified u sing the statistical approach of carbon black concentration distributi on in the extruded film mixed with a carbon black masterbatch. The res ults indicate that a free flight gives the lowest melt temperature ris e, pressure drop, and driver power, but the worst mixing; a holed-pin mixing section has better mixing ability, lower melt temperature rise, and lower driver power than a normal pin mixing section does; the val ue of the pressure drop of the two types of pin mixing sections is app roximately identical. A longer axial distance between the two pins in a holed-pin mixing section gives better mixing and lower melt temperat ure rise than a shorter one; however, when the distance is longer than a critical value, the improvement of mixing is not so outstanding; fo r different axial distances between two pins, no great change in press ure drop was found and the extrusion throughput has almost no great re lation to the axial distance.