The feeding section of the barrel is mostly water-cooled, which is locked with the second section (heating) with a flange, and the heat can be continuously conducted from the high-temperature barrel to the cold barrel. As a result, the second-stage barrel cannot maintain a sufficient temperature.
Usually, the operator sets a temperature of 180°C in the second-stage barrel, but due to heat loss in the feeding section, the stable temperature usually does not exceed 135°C.
The simplest solution is to add one or two 1mm thick insulation gaskets between the feeding section and the second section of the barrel flange and replace the insulation gaskets every few years because the insulation gaskets tend to age, degrade and shrink.
As you probably know, turbulent flow in a dual screw extruder water pump can result in more wall heat exchange than laminar flow. Turbulent flow in high-pressure transport has a high degree of lateral momentum exchange, which breaks the boundary layer. As a result, the vigorous fluid motion causes a large amount of heat exchange between the tube wall and the fluid.
The extruder cooling circulation system generally provides a pressure of 20 to 6OPSI. To achieve turbulent flow, a pressure of 120 PSI is best achieved. Almost all cooling system components (hoses and valves) of the extruder have to be upgraded to 150PSI to meet the 120PSI safety factor. After the transformation is completed, the cooling system can discharge a large amount of heat in time during processing.
Side feeders are commonly used to feed filler material into dual screw extruders. Many processors require very high loadings of fillers, which tend to have very low bulk densities. The final fill volume is governed by the following factors:
(1) The volume feeding capacity of the side feeder and the volume feeding capacity of the main screw of the extruder. The volumetric feeding capacity depends on the free volume of the side feeder and main screw, and the rotational speed of these two screws.
If a material can flow into the storage bag without being resisted by the main screw in the test, the material feeding rate can be achieved very well. If the side feeder is attached directly next to the main screw, the amount of material that the main screw can accept will be limited. Therefore, the main screw should preferably have a long-pitch threaded element extending 2D to 4D length downstream of the side feeding port. This will allow the melt to pass quickly through the side feeding ports, maximizing the intake of filler materials by the main screw. If the screw of the main motor causes any build-up of the side-feed material, it will severely limit the feeding capacity of the filler.
(2) The exhaust capability to allow gas to be discharged from the twin screw extruder. The purpose of the exhaust is to allow the air to escape easily, while also protecting the filler from escaping a lot from the exhaust port. The best configuration is to open an upwardly vented exhaust port upstream of the side feeding port. Sometimes a small half-slit vent is opened in the upper part of the side feeder.
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