The Structure and Working Characteristic of Twin Screw Extruder

01 Apr.,2024

 

Ⅰ. Structural characteristics of twin screw extruder


The twin screw extruder has the advantages of low heat generated by friction, uniform material shearing, large screw conveying capacity, stable extrusion molding, long barrel retention time, and uniform mixing.


The twin screw extruder has the characteristics of forced extrusion, high quality, considerable adaptability, long service life, low shear rate, difficult material decomposition, good mixing and plasticization performance, direct powder molding. It has the advantages of automatic temperature control and vacuums exhaust. It is suitable for producing silicone pipes, plates, profiles, and other products.


The screw and barrel of the twin screw extruder adopt an advanced "building block" design, and the screw is composed of various forms of screw blocks set on the mandrel. The inner liner in the cylinder can be adjusted according to the different screw blocks to flexibly combine the ideal threaded element structure according to the material variety and other technological requirements. Various processes such as material transportation, plasticization, refinement, shearing, exhaust, decompression, and extrusion are realized to solve the contradiction between the versatility and stability of the screw, which is generally difficult to balance and achieve the purpose of multi-purpose machine and multi-function of one machine.


Another advantage of the "building block" design is that the worn screw and barrel components can be partially replaced, avoiding a scrap of the entire screw or barrel and greatly reducing maintenance costs.


Ⅱ. Working characteristics of twin screw extruder


1. The twin screw extruder is mainly used to produce pipes, plates, pellets, and guide profiles. The output of extrusion molding is twice or higher than that of a single screw extruder, and the energy consumption is also lower than that of a single screw extruder.


2. Single-screw extruded plastic products need to be produced with pellets. At the same time, the dual screw extruder can directly add powder for extrusion because of its strong conveying capacity, eliminating the need for pelletizing procedures and reducing the processing cost of plastic products.


3. The dual screw extruder has a small shearing calorific value and does not require the high thermal stability of the material. It can reduce the amount of some stabilizers, and the toxic effect of the stabilizers is relatively reduced, and the cost is also reduced.


4. Compared with general batch or continuous reactors, the dual screw extruder has a thinner dispersion layer of molten materials and a larger melt surface area. The extremely thin, constantly renewing surface layer is conducive to chemical reactions' material transfer and heat exchange. The twin screw extruder can quickly and accurately complete the predetermined chemical changes during the transportation of the material.


The modified polymer that is not easy to prepare in a large stirred reactor can also be completed in a twin screw reaction extruder. The twin screw extruder is used for reaction processing. All have the characteristics of greater choice, simple operation, etc.