The most commonly used extruders for the processing of PVC plastics are equidistant unequal-deep-graded and equal-depth unequal-distance gradient single-screw extruders, and counter-rotating parallel twin-screw and conical twin-screw extruders.
Screw design principle a. Strict temperature control, screw design as low as possible to prevent overheating. b. Screws and barrels must be protected against corrosion. c. Injection molding process must be strictly controlled. In general, the screw parameters are L/D=16-20, h3=0.07D, ε=1.6-2, L1=40%, and L2=40%. In order to prevent the storage of materials, no negative ring, head taper 20 ° ~ 30 °, more suitable for soft rubber, such as product requirements are higher, can be used non-metering, separate screw, this screw is more suitable for rigid PVC And, in order to match the temperature control, add the cooling water or oil hole inside the screw section of the feeding section, add the cold water or oil tank to the barrel, and the temperature control precision is about ±2°C.
When soft PVC granulation adopts co-rotating twin-screw extruder, the Luogan conveying compression section should use high-transport efficiency, and it is a structural design that is gradually compressed. Mixing and conveying the dispersion section should reduce the temperature difference and fluctuation, and ensure high mixing efficiency and quality. The exhaust section ensures that the vapors are fully volatilized and discharged, the compression section has an appropriate length-diameter ratio, and the metering section ensures that the material is uniformly extruded. In general, for a screw with a length-to-diameter ratio of 32, the general compression section L/D=11~12; the mixing and conveying section L/D=8~9; the exhaust section L/D=3~3.5 The compression section L/D=5~8; the measurement section L/D=3~4.
For the formation of rigid PVC products such as PVC profiles/pipes, the conical twin-screw extruder has outstanding advantages and is also a mainstream machining model. In the same helical structure, although the length of the parallel twin screw is 60% longer in the feed section than in the conical twin screw, the heat transfer area is 45% smaller. When the conical twin screw is transported, the relative movement speed between the materials is greater than that of the parallel twin screw. The screw, ie, the conical screw, generates more shear heat than the parallel screw. Therefore, the conical double screw in the feed section is superior to the parallel screw in plasticizing the material. In addition, the conical twin-screws have reduced their screw groove volume in the conveying process, and the extrusion effect is enhanced, so that the material and the screw are in full contact, so that the conical screw can provide a higher energy conversion, so that the pre-plastic effect better. In the metering section, because of the smaller diameter of the screw, the conical twin-screw attenuates the shearing action of the material and produces a smaller shear heat, which just meets the UPVC plastic extrusion requirements.
Screw design principle a. Strict temperature control, screw design as low as possible to prevent overheating. b. Screws and barrels must be protected against corrosion. c. Injection molding process must be strictly controlled. In general, the screw parameters are L/D=16-20, h3=0.07D, ε=1.6-2, L1=40%, and L2=40%. In order to prevent the storage of materials, no negative ring, head taper 20 ° ~ 30 °, more suitable for soft rubber, such as product requirements are higher, can be used non-metering, separate screw, this screw is more suitable for rigid PVC And, in order to match the temperature control, add the cooling water or oil hole inside the screw section of the feeding section, add the cold water or oil tank to the barrel, and the temperature control precision is about ±2°C.
When soft PVC granulation adopts co-rotating twin-screw extruder, the Luogan conveying compression section should use high-transport efficiency, and it is a structural design that is gradually compressed. Mixing and conveying the dispersion section should reduce the temperature difference and fluctuation, and ensure high mixing efficiency and quality. The exhaust section ensures that the vapors are fully volatilized and discharged, the compression section has an appropriate length-diameter ratio, and the metering section ensures that the material is uniformly extruded. In general, for a screw with a length-to-diameter ratio of 32, the general compression section L/D=11~12; the mixing and conveying section L/D=8~9; the exhaust section L/D=3~3.5 The compression section L/D=5~8; the measurement section L/D=3~4.
For the formation of rigid PVC products such as PVC profiles/pipes, the conical twin-screw extruder has outstanding advantages and is also a mainstream machining model. In the same helical structure, although the length of the parallel twin screw is 60% longer in the feed section than in the conical twin screw, the heat transfer area is 45% smaller. When the conical twin screw is transported, the relative movement speed between the materials is greater than that of the parallel twin screw. The screw, ie, the conical screw, generates more shear heat than the parallel screw. Therefore, the conical double screw in the feed section is superior to the parallel screw in plasticizing the material. In addition, the conical twin-screws have reduced their screw groove volume in the conveying process, and the extrusion effect is enhanced, so that the material and the screw are in full contact, so that the conical screw can provide a higher energy conversion, so that the pre-plastic effect better. In the metering section, because of the smaller diameter of the screw, the conical twin-screw attenuates the shearing action of the material and produces a smaller shear heat, which just meets the UPVC plastic extrusion requirements.
99.99% Nitrogen Generator,High Purity Nitrogen Generator,Nitrogen Generator Industrial,Nitrogen Generator Equipment
Jiangsu Minnuo Group Co.,Ltd , https://www.mingngroupcn.com