TWIN SCREW

สกรู บาร์เรลและอะไหล่ สำหรับงาน Extrusion

a. twin screw barrel สำหรับงานเป่า

b. conical twin screw สำหรับงานท่อ

Twin Screw Extruders for the compounding of engineering thermoplastics

1-Introduction Polymers are blended with their compounding ingredients in extruders. The blending of basic components such as antioxidants and light stabilisers is done either during the last stages of the polymerisation process or soon after in an extrusion step which is followed by granulation. In fact most if not all plastic granules sold in bags, have been subjected to the effects of heat as well as shear, once after their production and another time at the compounders who produce special grades and colours. Compounding extruders are classified in single screw and twin screw extruders. The mixing effect of single screw extruders relies on the shear generated between the walls of the barrel and the screw. The shear mixing of twin screw extruders is more efficient and as a result the polymer is subjected to less thermal history.

Twin screw extruders, are used for bulk polymerisation, processing (pipes, sheet..) or compounding. Bulk polymerisation twin screw extruders are used in the manufacture of TPU, POM etc. Twin screw extruders are also used, like single screw extruders in the manufacture of finished products such as pipes and sheet. This short article will be confined to giving an account on twin screw extruders used in the compounding of engineering thermoplastics. In this case the extrudate takes the form of thin rods which are pelletised. The pellets are injection moulded.

2-Twin screw extruders-a classification