First of all, the extrusion principle of the single screw extruder is possessed by the double screw extruder: solid delivery, melting, pressurization, gas mixing and devolatilization are pumped together. However, it is not solely like that. The research of the double screw extrusion theory started late, and coupled with its various types, complex screw geometry, and complex extrusion process, this brings many difficulties to the research.
On the whole, the research of the extrusion theory of the double screw extruder is still in its initial stage, which is referred to as "more skilled than scientific".
In terms of the study of the extrusion process of the double screw extruder, it can be divided into three stages:
The mathematical and physical models are established to guide the design and optimization of the extrusion process of the double screw extruder by studying the law of the change of state of polymers in the extrusion process, the solid-to-melt delivery principle, the exhaust truth and law.
The process of the changes in the state, the mixing form, the structural changes, and the relationship between the post-mixed material and the performance of two or more polymers and materials in the extrusion process, respectively should be clarified.
As a double screw extruder, the intrinsic relationship between the reaction process, speed, performance and screw configuration, and operating conditions at the time of extrusion reaction molding, establishes a model to guide reaction molding extrusion.
It was first developed in Italy in the 1930s and developed rapidly from the late 1960s to the early 1970s. The meshing type and the hetero-directional twin screw were developed with the development of RPVC products, and the same direction twin screw extruder was developed with the development of polymer modification. The research of double screw extrusion theory cannot adapt to the application development, which has formed a consensus worldwide and has become a research hotspot.
Heat double screw extruder to ensure that the temperature of the fuselage, head, die head, and control points are within the specified range.
If it has not been used for a long time and is restarted, after the temperature at each point reaches the target range, it needs to be kept at the constant temperature for 10-30 minutes. If it is restarted within half an hour, it does not need to be kept at the constant temperature.
Start the air compressor and stop when the storage cylinder pressure reaches 6-8kg/cm.
According to the requirements of the film folding diameter and thickness, the processing capacity of the double screw extruder is operated, and the traction speed and steady bubble diameter are estimated.
After the temperature at all points reaches the specified range, wear safety equipment in order, and start the traction machine, blower, and extruder.
Check the thickness and width of the film at all parts of the plastic blown film machine and adjust them to meet the requirements.
When the material is evenly discharged from the die mouth, slowly lift the pipe blank while closing the end of the pipe blank, and blow a small amount of compressed air from the center hole of the mandrel.
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