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The function of the rubber extruder machine is to use heat, pressure and shear to transform solid plastics into a uniform melt and send the melt to the next process. Melt production involves the mixing of additives such as color masterbatches, resin blending, and repulverization. The finished melt must be uniform in concentration and temperature. The pressure must be large enough to squeeze out the viscous polymer.
The rubber extruder performs all the above processes through a barrel with a screw and a spiral. The plastic pellets enter the barrel through a real hopper of the barrel, and then are transferred to the other end of the barrel through the screw. In order to have sufficient pressure, the depth of the thread on the screw decreases as the interval to the hopper increases. External heating and internal heat generated by friction between the plastic and the screw soften and melt the plastic. Different polymers and different applications often have different requirements for the design of the extruder. Many options involve discharge ports, multiple feed ports, special mixing devices along the screw, cooling and heating of the melt, or no external heat source (heating extruder). The gap between the screw and barrel changes relatively. Size, and the number of screws. For example, a twin-screw extruder allows the melt to be more thoroughly mixed than a single-screw extruder. Tandem extrusion is the melt extruded by the first rubber extruder and used as the raw material for the second rubber extruder. It is usually used to produce extruded polyethylene foam.
The characteristic dimensions of a rubber extruder are the diameter (D) of the screw and the ratio (L / D) of the length (L) to the diameter (D) of the screw. The extruder usually consists of at least three stages. The first section, near the feeding hopper, is the feeding section. Its function allows the material to enter the rubber extruder at a relatively stable rate. In general, in order to avoid blockage of the feeding channel, this part will be kept at a relatively low temperature. The second part is the compression section, where a melt is formed and the pressure increases. The transition from the feeding section to the compression section can be sudden or gradual (gradual). The last part of the metering section is next to the rubber extruder exit. The main function is that the material flowing out of the rubber extruder is uniform. In this part, to ensure the uniformity of composition and temperature, the material should have sufficient residence time.
At the end of the barrel of the rubber extruder, the plastic melt exits the rubber extruder through a head. This rubber extruder head is designed to the ideal shape, and the extruded melt flow passes here. Another important part is the driving mechanism of the rubber extruder. It controls the rotation speed of the screw, which determines the output of the rubber extruder. The required power is determined by the viscosity (resistance to movement) of the polymer. The viscosity of the polymer depends on the temperature and the rate of activity, and it decreases with the increase of temperature and shear force.
The rubber extruder is equipped with a screen, which can block impurities on the screen. To avoid downtime, the filters should be able to be replaced automatically. This is especially important when processing resins with impurities, such as recycled materials. The screw of the extruder is divided into the feeding section, the plasticizing and melting section, and the temperature is based on the plastic particle process parameters. The model is divided into 20, 36, 52, 65, 75, 95, 120, and 135 according to the screw diameter. After the plastic particles are heated, the original state is changed by the movement of the screw. There are many types, depending on the specific application. The capacity of the frequency conversion is proportional to the diameter of the screw, and then adjusted according to the different raw materials.