Asia Rubber Expo & Rubber Tech India 2020" is co-sponsored by AAKAR Exhibition Company and Zhonglian Rubber Co., Ltd. The exhibition will be held in the Chennai Trade Center (CTC) of India from 8 ...Read More
The function of the rubber extruder machine is to use heating, pressure and shearing methods to transform solid plastic into a uniform melt and send the melt to the next process. The production of the melt involves the process of mixing additives such as color masterbatch, blending resin and pulverizing. The finished melt must be uniform in concentration and temperature. The pressure must be large enough to extrude the viscous polymer.
The rubber extruder completes all the above processes through a barrel with a screw and a spiral channel. Plastic pellets are fed into the barrel through a hopper, and then conveyed to the other end of the barrel through a 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 cause the plastic to soften and melt. Different polymers and different applications often have different design requirements for extruders. Many options involve discharge ports, multiple feeding ports, special mixing devices along the screw, cooling and heating of the melt, or no external heat source (exhaust heat extruder), the gap between the screw and the barrel changes relatively Size, and the number of screws, etc. For example, a twin-screw extruder can mix the melt more fully than a single-screw extruder. Tandem extrusion is to use the melt extruded by the first rubber extruder as a raw material to supply the second rubber extruder, usually used to produce extruded polyethylene foam.
The characteristic size of a rubber extruder is the diameter (D) of the screw and the ratio (L/D) of the length (L) of the screw to the diameter (D). 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 steady rate. In general, in order to avoid blockage of the feeding channel, this part will maintain a relatively low temperature. The second part is the compression section where the 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 close to the exit of the rubber extruder. The main function is that the material flowing out of the rubber extruder is uniform. In this part, in order to ensure the uniformity of composition and temperature, the material should have enough residence time.
At the end of the barrel of the rubber extruder, the plastic melt leaves the rubber extruder through a die. The die of the rubber extruder is designed with an ideal shape, and the extruded melt flows through here. Another important part is the drive 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 (movement resistance) of the polymer. The viscosity of a polymer depends on temperature and activity rate, and decreases as temperature and shear force increase.
The rubber extruder is equipped with a filter screen, which can block impurities on the filter screen. To avoid downtime, the filter screen 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 feeding section, plasticizing and melting section. The temperature is based on the process parameters of the plastic particles, and the model is divided into 20, 36, 52, 65, 75, 95, 120, 135 according to the screw diameter. After the plastic particles are heated, the original state is changed by the movement of the screw, and 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.
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