The screw combination is generally divided into five parts, conveying section, melting section, mixing section, exhaust section, and homogenizing section.
1.1 Conveying section is to convey materials and prevent overflow. A conventional large-lead screw element is suitable.
1.2 Melting section is to make the material fully melted and homogenized through heat transfer and frictional shearing. The screw elements should be according to material requirements
1.3 In the mixing section, the size of the material components is further refined and uniform, forming an ideal structure, and has the function of distributing and dispersing mixing. A kneading block should be used.
1.4 The exhaust section discharges impurities such as water vapor and low molecular weight substances.
1.5 Homogenization (metering) section is for conveying and pressurizing to establish a certain pressure, so that the material at the die mouth has a certain density. While further mixing, the goal of smooth extrusion and granulation will finally be achieved.
2.1 Distributed mixing is the process of segmentation and reorganization of the melt to uniform spatial distribution of each component, mainly through separation, stretching (alternatively produced by compression and expansion), distortion, fluid activity reorientation and other stresses to achieve displacement flow.
2.2 Disperse mixing is to break the components into particles or make the size of the incompatible two-component dispersed phase reach the required range, which is mainly achieved by the kneading block shear pressure and extension stress.