Main factors affecting plasticizing quality
Main factors affecting plasticizing quality The main factors affecting plasticizing quality are: length-to-diameter ratio, compression ratio, back pressure, screw speed, and barrel heating temperature, etc. Length-to-diameter ratio: the ratio of the effective working length of the screw to the diameter of the screw. a.A larger length-to-diameter ratio makes feeding more uniform; b.Plastics with better thermal stability can use longer screws to improve compounding without burning, while plastics with poor thermal stability can use shorter screws or screws without threads at the end. Considering the plastic characteristics, the length-to-diameter ratio is generally as follows: 14-16 for thermosetting plastics, 17-18 for rigid PVC, high viscosity PU and other thermosensitive plastics, 18-22 for general plastics, and 22-24 for high-temperature stable plastics such as PC and POM. Compression Ratio: the ratio of the last depth of the screw in the feeding section to the first depth of the screw in the metering section. a. Considering the compressibility of the material, filling degree, backflow and other factors, the product should be compact, with good heat transfer and ventilation. b. Appropriate compression ratio can increase the density of plastic, make the binding between molecules more tight, help reduce the absorption of air, lower the temperature rise caused by pressure, and affect the difference in output. Improper compression ratio will destroy the physical properties of plastic. c. The higher the compression ratio, the higher the temperature rise of the plastic during the plasticization process in the barrel, and the better the mixing uniformity of the plastic in
