The role and selection of melt pumps for plastic film extruders
Plastic extrusion melt pumps are mainly used for stabilizing, pressurizing and conveying polymer flow layers in medium or high viscosity media. The use of melt pumps is more effective when extruding films and thin-walled profiles. This is because the use of melt pumps homogenizes the plastic melt and reduces fluctuations in the pressure and flow rate of the melt conveyed by the extruder, which plays a decisive role in obtaining high quality products, especially those of uniform thickness. In particular, the production of film or ultra-thin films such as PET, PS, PP and to high directional film when the melt pressure and flow instability is particularly sensitive to the existence of excessive pulsation amplitude or raw materials are contaminated by impurities or the formation of gel glumes, it is easy to melt mixing and homogenization quality is reduced, it is virtually impossible to produce high-quality directional film in a stable process state, and the melt pump can solve this problem.
Although the plastic film extruder melt pump in the plastic extrusion system has been widely used, but in the processing of plastics containing fillers or special modifiers in the application is still limited, it is the dispersion of the components, and plastic compatibility and abrasiveness have strict requirements. Containing large particles, abrasive filler or enhancer materials can not be processed with extruders equipped with melt pumps, because the contained filler cis-grain easy to form a material plug, and the material plug can not pass through the gap between the teeth of the melt pump meshing gear, and the plug and abrasive wear of the teeth will make the melt pump quickly damaged. In addition, the fine mineral filler can also cause the above results, because this filler and plastic compatibility is not good, in the high-speed shear zone can not be sheared and gradually formed to damage the melt pump plugs.
High temperature melt pump in the plastic extrusion has been quite widely used. Along with the rapid development of the plastics industry, especially the proportion of blended materials increase, as well as the use of melt pump technology in the extrusion system continues to improve, the application of melt pumps for plastic extrusion will continue to broaden and develop the city. The polymer extrusion melt pump provides pressure between the extruder and the die, and can match the parameters of the extruder to provide a uniform melt in the case of increased output and tight tolerance requirements. It is generally installed between the extruder outlet and the head and is widely used in polymer extrusion molding such as pelletizing, film, pipe, sheet, and sheet, etc. It can also be installed in the pipeline to convey high viscosity pure materials. ZB-B, ZB-C and ZB-H series melt gear pumps are made of high temperature alloy steel and powder alloy steel. After a series of thermal processing and surface treatment, such as high temperature quenching, tempering, tempering, nitriding, carburizing, carbo-nitriding and polishing, the products have the characteristics of high temperature resistance, high pressure, high wear resistance and corrosion resistance, etc. The hardness of the products can reach 62-68HRC, which can greatly meet the requirements of customers for different working conditions.
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