Temperature index and control method of the hottes

2022-08-03
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According to the melting theory of plastics, the extruder screw of blown film is divided into three sections: feeding section, melting section and homogenizing section. At the end of feeding section and at the beginning of melting section, according to melting theory, its temperature should be viscous flow temperature. The viscous flow temperature of various blowing resins is PP: Celsius, PE: Celsius, PA: Celsius

at the inlet of the feeding section, the temperature should be lower to prevent the resin viscous flow from blocking the feeding port. In addition, in the feeding section, the resin is continuously compressed, and the air should be discharged from the feeding port upside down. According to different equipment structures, although the feeding port is not electrically heated by various means, the temperature of the feeding port is about degrees through the heat transfer of the barrel. In this way, the temperature of the feeding section is determined. The temperature at the entrance is equal to the melting point or viscous flow temperature at the end. In this section, the temperature can be determined as the proportional linear temperature rise

at the beginning of the melting section, the temperature reaches the viscous flow temperature before melting. For crystalline resin, the viscous flow temperature is equal to the melting point temperature. Then the continuous compression and increase of the melting layer requires the continuous increase of the temperature, so that the length of the resin molecular chain is different, and the polymers with different thermal motion energy are melted successively. Therefore, the vertical universal tensile testing machine and the horizontal tensile testing machine at the end of the melting section are divided into vertical universal tensile testing machine and horizontal tensile testing machine. After the temperature is established, it can be determined that other parts of the section are heated linearly

in the homogenization section, it is mainly remelting homogenization and quantitative constant pressure constant temperature output melt. The temperature in this section can be kept constant, or the temperature at the end of the melting section increases slightly (about degrees)

for film blowing, it is required that the temperature of the head section should be lower, but not lower than the viscous flow temperature, so as to facilitate film lifting and normal film blowing. The melt must have a certain viscosity when coming out of the die mouth, so as not to break or collapse the film. In general, it is about lower than the end of the homogenization section, and the temperature from the homogenization section to the nozzle can also be regarded as the differential temperature drop

the key points to control the extrusion temperature are as follows:

different resins have different blowing film process temperatures

the resin is the same as the latest data of the Institute of high technology industry. The model and melt index are different, and the process temperature of film blowing is different. The resin with large index has good fluidity and low temperature

for the same resin, the process temperature is also different for blowing films with different thickness. For processing thick films, the process temperature can be higher, and the temperature of the die can also be higher, which is conducive to reducing viscosity and improving productivity

Author: chenmatashan

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