Co-extrusion process control

日期:2021/10/9 8:39:51 / 阅读: / 来源:本站

Co-extrusion process control

     Co-extrusion method Co-extrusion method allows multiple melts to be laminated together (usually multiple extruders are used to feed through the same die). This method uses melt heat to stick various plastics on the block. The co-extrusion method is very economical because it reduces the cost of material processing, raw material cost and machine time cost. Using an extruder to squeeze the melt into a two-layer structure can also achieve good results.

       For the co-extrusion method, how to control the thickness of each layer is often the most difficult problem for the operator to solve. This problem involves the performance of the raw materials of each layer, the design of the die head and the processing quality, and the yield rate, etc., which requires the operator Negotiate with engineering and technical personnel to find out its adjustment rules. When there are two or more extruders feeding at the same time, the extruder should be calibrated according to the ratio of production rate and rotation speed (a gear pump can be used), and then the width, thickness, and stretching speed of the product should be determined, and respectively Calculate the yield of each raw material. Use its yield result together with the calibration curve to determine the screw speed. When the design of the common material die is improper, there will be excessive pressure drop, excessive shear rate, and long residence time. These factors will affect the quality of each layer of the product. Multiple extruders transfer the melt to the die at the same time. The transfer device such as the extruder connector pipe may be designed to be short or long, but in any case, the inner diameter of the pipe should be large enough to avoid excessive Large pressure drop, but not too large, otherwise it will increase the melt retention time. The temperature is required to be uniform, to avoid uneven temperature distribution caused by the use of heating coils, such as local overheating or overcooling. It is recommended to use a low-pressure heater. In addition, the location of the thermometer is also very important. If a certain area is overheated, it may degrade the material into gas and generate high pressure.

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