A collection of problems in the production process of PVC pipesA collection of problems in the production process of PVC pipes
Every new operator must have encountered a lot of big and small questions when operating PVC pipe equipment.Here are some solutions to the conventional questions.
Main points of PVC pipe production process control
1. Process temperature: During start-up and normal production, temperature is one of the main factors affecting plasticization and product quality. Polyvinyl chloride plastic has poor thermal stability and is easy to decompose at high temperature. The temperature of each section must be strictly controlled; if the temperature is too low, the plasticization is not good, and the quality of the pipe is poor; if the temperature is too high, the material is easy to decompose. The specific operating temperature should depend on the raw material formula, extruder and head structure and screw speed.
2. Screw cooling: Hard polyvinyl chloride has a high melt viscosity and poor fluidity. In order to prevent the temperature of the screw from rising due to excessive friction heat and decomposing the screw sticky material, the screw must be cooled.
3. Screw speed: The choice of screw speed has a direct impact on output and quality. The screw speed should be determined according to the size of the extruder and pipe diameter. The screw speed for extruding rigid PVC pipe is 7-30 rpm. Increasing the rotation speed can increase the output, but if simply increasing the rotation speed, the material will be poorly plasticized, the inner wall will be rough, and the strength of the pipe will decrease. Therefore, the screw speed should be matched with other extrusion conditions.
4. Traction speed: In normal production, the traction speed is 1% to 10% faster than the extrusion speed of the pipe to overcome the film expansion of the pipe. The traction speed should not be too fast or too slow. If it is too fast, the pipe is easy to bend and deform. Too slow, due to the expansion of the membrane, the pipe wall will be thickened.
5. Compressed air: Compressed air can shape the tube and maintain a certain roundness. Compressed air pressure usually needs to be stable to ensure that the pipe has a certain roundness; the pressure is suddenly large and small, and the pipe is prone to slub shape. The pressure is generally 0.02 to 0.05 MPa.