| Polymer is a kind of material that is applied in a broad area. It is a kind of big molecule, which is composed of many small molecules. The polymer has a structure of chain or reticulation. About 80% polymer process needs extrusion. The extruder is a kind of important equipment. Along with the development of science and engineering, more reactions have been processed in the extruder. Many chemical cells can be incorporated through extruder. The intermittent operation can be replaced by the continuous operation through extruder. The production efficiency can be increased and the energy can be reduced. Because the automation degree of extruder is higher, it can reduce pollution, improve work conditions. So extrusion technique has been applied in polymer process.Since rubber extruder came out 100 years ago, the cold feed extruder has replaced hot feed extruder, which is a technical breakthrough. For cold feed extruder, the rubber process can be divided into mixing technique and molding technique. A lot of products can be manufactured by the cold feed extruder economically. The key is how to heat up the cold feed extruder equably and improve extrusion efficiency. The pin barrel extruder appeared about in the 1970, which is a breakthrough of cold feed extruder. It improves cold feed extruder performance. So, the pin barrel extruder has been the research focus of rubber process technique in recent 30 years.Because of the complexity of rubber process, there is localization in the theory and computation method of rubber process, which relies on experiential method. Along with the deep comprehension, accumulated practice and the rapid development of computer, now the problem of polymer process can be settled by simulation technique. The computer can display process course, forecast the equipment performance, optimize the parameters of structure and operation. So the operation of injection, extrusion, extension and mixing can be optimized. Only by computer simulation, can the request of high quality and high output for the polymer process be satisfied. From experience analysis to computer simulation, it is a transformation of rubber process research method.Because many pins are fixed in the barrel, the material flows complexly in the channels. It is impossible to solve the complex flow accurately now. Only by finite elementmethod, can the numerical value be got.Based on the simplified model of the single screw, the soft ware GAMBIT was adopted to process the models in advance. First, geometrical models were constructed. Second, the meshes were plotted. The area around pins was plotted as sliding meshes, and other area were plotted as actionless meshes. Last, the boundary conditions were set up and the two kinds of meshes were incorporated. After that the results of GAMBIT were processed by the finite element soft ware FLUENT. The flow distributions of every kind of model were got: different numbers of pins, different width of grooves, different daggling velocities. It can be seen through the analysis of FLUENT that the material goes through landscape orientation movement, diffluent movement and circumrotating movement under the influence of the pins. Because the existence of the pins, the geometrical figure of flow channels were changed. The flow layers were attenuated. The extension flow came into being. So we can say that the structure of pins can affect the flow of material notably. It can be seen from the analysis results of FLUENT that the velocity grads are higher on the condition that the channels of screw are narrower and the row distance of pins is smaller. Higher velocity grads are in favor of mixing. If the daggling velocity changes, the flow distribution changes a little. In this simplified model, it was considered that the movement of material was in virtue of the daggling effect of the inner barrel. But in fact, it is the ridges of screw that push the material forward. There are differences between this model and facts. But the results still play an important role in analyzing flow distributio... |
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