Soft PVC pipe production process: extrusion molding process

The screw of the extruder is divided into 3 sections: feeding section (feeding section), melting section (compression section), metering section (homogenization section), these three sections correspond to the material to form 3 functional areas: solid conveying area, Material plasticizing area, melt conveying area.

     The barrel temperature in the solid conveying area is generally controlled at 100-1400C. If the feeding temperature is too low, the solid conveying area will be extended, reducing the length of the plasticizing zone and the melt conveying zone, which will cause poor plasticization and affect product quality.

     The temperature in the material plasticizing zone is controlled at 170-1900C. Controlling the vacuum degree of this section is an important process index. If the vacuum degree is low, the exhaust effect will be affected, resulting in air bubbles in the pipe, which seriously reduces the mechanical properties of the pipe. In order to make the gas inside the material escape easily, the degree of plasticization of the material in this section should be controlled not to be too high, and the exhaust pipe should be cleaned frequently to avoid blockage. The vacuum degree of barrel is generally 0.08-0.09MPa.

      The temperature in the melt conveying area should be slightly lower, generally 160-1800C. Increasing the screw speed in this section, reducing the resistance of the machine head and increasing the pressure in the plasticizing zone are all conducive to the improvement of the conveying rate. For heat-sensitive plastics such as PVC, the residence time in this section should not be too long. The screw speed is generally 20 —30r/min.

The head is an important part of extrusion molding, and its function is to generate high melt pressure and shape the melt into the desired shape. The process parameters of each part are: die connector temperature 1650C, die temperature 1700C, 1700C, 1650C, 1800C, 1900C.