| Polymer processing is a high-energy process operation, and screw machinery is widespread applied to the polymer processing, such as screw extruders, screw injection molding machine and so on. The screw plasticating and conveying equipments based on shear rheology are generally adopted in polymer processing, in which materiels are dominated by shear stress. Therefore, there are some ubiquity disadvantages of the current methods of polymer materials processing, such as long thermo-mechanical, high energy consumption, too big equipment structure, and dependence on material properties. Jinping Qu, the professor of SCUT has put forward and invented a polymer vane plasticating and conveying method based on elongational rheology which is different from the one of the screw plasticating and conveying and it can make the flow and deformation of polymer dominated by elongational stress field. The method has many advantages over conventional plasticating method, such as shorting thermo-mechanical experience of plasticating and conveying, reducing the energy consumption of plasticating and conveying, and improving adaptability to diverse materials. Therefore, study of the impact on polymer by experiment and theory ways will bring out great science and realistic significance.The principle of polymer vane plasticating and conveying method based on elongational rheology was analyzed in this paper. The axial rectangular slot squeezing flow model and circumferential converging wedge channel flow model were established according to the basic structure and working principle of vane unit, and combined with the necessary assumption, the expressions of velocity distribution, pressure distribution, strain distribution of melt in the vane unit were analyzed and discussed. Elongational flow field of vane extruder was expressed quantificationally for the first time, and it proved that melt conveying in vane extruder was controlled by elongation field. Based on the analysis of flow filed, the influence of periodically normal stress field and elongational flow field to microstructure and molecule of polymer under vane extruder procesing were discussed, and affirmed that periodically normal stress field and elongational flow field were the key factors of energy saving and high effect to the transportation and plasticization of polymer.As opposed to screw extruder, the transmission capacity and product testing processed by vane extruder were studied through a large number of experiments in this paper. The vane extruder with rotator diameter ? 40 and aspect ratio 10, and the screw extruder with rotator diameter ? 45 and aspect ratio 20 were used to the conveying experimental studies by processing HDPE, LDEP and PP respectively. At the same time, the mechanical properties, thermal properties, micro-structure of the products of LDPE, PP, LDPE/na-no CaCO3, PP/na-no CaCO3 processed by vane extruder and screw extruder were tested.Results from theory analysis and experiment revealed that: comparing with screw extruder, vane extruder proved that the device is reliable, efficient with improved production quality and lower energy consuming. The mechanics properties of samples of LDPE, PP processed by vane extruder are better than the samples porceessed by screw extruder, and the thermal properties and micro-structure also improved. For the filling system of LDPE/na-no CaCO3, PP/na-no CaCO3, the samples processed by vane extruder can improve the best mechanics properties of fill ratio to 2%～3% compared with screw extruder samples.The comparison of the results coming from the theoretical calculation and the experiment reveals that these theory models are valid and useful. This study will serve as the theory and experiment basis for the optimum conditions of vane extruder design and processing polymer. |
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