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With China Plastic Machinery
With China Plastic Machinery
A melt extruder refers to a screw extruder whose feed material is a melt (or polymer solution). This type of extruder is widely used in the polymer processing industry.
The function is to pump, pressurize and mix the melt. From these functions, the melt extruder can also be considered as a special form of screw pump.
According to the functional requirements of the melt extruder, compared with the plasticizing extruder, it has the following characteristics:
(1) The screw diameter can be selected to be larger. This is because the quality of the melt being transported is less affected by the screw diameter and the depth of the screw groove. For example, the maximum diameter can reach 300mm.
(2) The screw length-diameter ratio is relatively small, generally not exceeding 22. Obviously, this is because the melt extrusion screw is not responsible for solid conveying and molten materials.
(3) The screw structure does not necessarily adopt a three-stage segmentation, such as a long-zone gradient full-cone structure. Generally, only mixing elements are required, and shearing elements are only installed when there is a special need.
(4) To prevent shear overheating, the screw speed can be taken as a lower value. At the same time, the required driving power is also small. According to the principle of self-heating extrusion, if the screw speed is high, the heating power must be very low.
(5) The main function of the barrel heater is to maintain the melt temperature. Therefore, the required heating power is relatively low. Generally, there is no cooling device in the feeding area. For the extruder responsible for conveying delicate materials, a cold air system can be installed along the barrel to prevent overheating. The temperature control system is relatively simple.
(6) Generally, no feeding hopper or silo is configured, and the melt is directly fed into the melt through a melt pipe.
In the polymer processing industry, melt extruders are used for melt conveying, batching, etc.
Melt extruders are used in the discharge of polyester continuous polycondensation reactors. The interior of the polyester continuous polycondensation reactor is in a vacuum state. In order to discharge the high-humidity melt smoothly, a discharge screw with a feed spiral belt is installed at the discharge port of the polycondensation reactor.
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