Research On Melting And Plasticizing Under The Coupled Action Of Barrel Groove And Screw Channel

Because of the characteristics of stable extrusion, cost-effective, and simple operation, single screw extruder plays an important role in the field of polymer processing. With the development of social economy and the progress of science and technology, the production and the use of plastic products are developing continuously and rapidly. The production and plasticizing quality of traditional single screw extruder has been unable to meet people's demands for plastic products.A large number of studies have shown that although the solid conveying capacity increased by using grooved barrel in single screw extruder, it cannot match the melting rate. Therefore, the solid conveying efficiency cannot be shown and plenty of quality defects exists in the products. In this study, the grooves were extended from the solid conveying section to the melting section of the barrel. A melting model of the materials under the effect of coupling of the barrel grooves and the screw grooves was established and the mechanism of the barrel grooves on the plasticizing progress of the single screw extruder was revealed by the comparative experiments.1?On the basis of the existing experimental conditions, a visual function of the hydraulic drive split barrel single screw extruder experimental platform had been designed and constructed, which can offer intuitive observation of the melt plasticizing process in single screw extruder.On the basis of the existing experimental conditions, a single screw extruding experimental platform with hydraulic drive split barrel was designed and constructed. The melting state of the materials during the plasticizing process could be observed. The barrels and the screws with various structures were designed and manufactured, and the extrusion system of the single screw extruder with various functions was formed by the combination of the barrels and the screws.2?The material transport mechanism and the melt plasticizing process of single-screw extruder with different structures are discussed in details. Based on the theoretical analyses and experimental studies, the physical model and the mathematical model of the melting section grooved barrel are constructed,and the melting process parameters of the model are simulated. The effects of different screw speed and different barrel structure properties on the plasticizing performance of single screw extruder is analyzed.The material conveying mechanism and the plasticizing process of the single-screw extruders with smooth barrel and grooved barrel were discussed.The melting model under the coupling effects of the barrel grooves and the screw grooves was established, and the parameters in the melting process of the model were simulated. The effects of the geometry structures and the processing parameters on the plasticizing performance of the single screw extruder with grooved barrel were studied theoretically.3?The physical model and the mathematical model of the melting section grooved barrel are evaluated by the aspects of material system, technological condition and screw structure. The effects of screw speed and melting section barrel temperature on melt starting point, melting lengths, melt temperature/pressure, residence time and output of plasticizing process in grooved barrel extruder are studied. The results show that the reverse compression screw is more suitable for the extrusion system of single screw extruder for melting section groove barre. Solid conveying capacity and plasticizing ability have good matching effect, which ensuring high yield with excellent plasticizing effect. With the screw speed increasing, the melting lengths of plasticizing process is gradually reducing in screw channel, while the position of melt starting point is almost unchanged. It is shown that the shear heat generated by the shearing action of melt section barrel grooves and the screw channel is the main heat source in plasticizing process.The plasticizing model of the groove barrel in the melting section was evaluated by the aspects of material system, processing condition and screw structures. The effects of screw structures and processing conditions on the melting point, melting lengths, melt temperature/pressure, residence time and output of the plasticizing process in grooved barrel extruder were studied. The results showed that the main heat source of the melting process was generated by the coupling of the barrel grooves and the screw grooves in the melting section. The thick melting films were formed rapidly, and the solid state in the screw grooves was melted. The reverse compression screw was more suitable for the extrusion system of the melting section in the single screw extruder with grooved barrel, and the plasticizing effects were excellent as the output was high.4?The plasticizing properties of the single screw extruder with smooth barrel, solid conveying section groove barrel and melting section groove barrel were studied by comparative experiments using the extrusion system of forward compression screw, reverse compression screw and separated screw.The influences of the barrel structures on the plasticizing process of single screw extruder was revealed from the melting point, melting lengths, melt temperature/pressure and output. The results showed that the solid conveying capacity increased significantly when the spiral groove was formed in the inner wall of the solid conveying section of the barrel. Due to the weak capacity of plasticizing and conveying in the melting section of the smooth grooved barrel, solid conveying capacity and plasticizing capacity does not match, resulting a formation of blockage in the end of the solid section, and the pressure increased sharply in the melting section. With the coupling of the grooves of barrel and screw in the melting section, the material conveying rate and melting rate accelerated and the blockage was effectively dispersed. The melting lengths of the solid state during the plasticizing process in the screw grooves were obviously shortened and the pressure distribution of the melting section was more reasonable.