Study On Process And Mechanism Of Polyolefin Melting Plasticization In Uniaxial Eccentric Rotor Extruder

Melt plasticization is the core function of the extruder,which greatly affects the quality of extruded products and energy consumption for processing.Research on energy-efficient extruder for efficient melt plasticization is an urgent need in the field of polymer processing and molding.Different from the traditional screw extruder,the uniaxial eccentric rotor extruder is a polymer processing equipment based on a completely new mechanical structure and processing principle.The polymer's melt plasticization process has changed significantly.Traditional screw extrusion theory does not suitable for uniaxial eccentric rotor extruder.Previous research showed that the eccentric rotor extruder not only has better product performance but also lower processing energy consumption.This processing advantage is closely related to its unique melt plasticization method.It is particularly important to study the melt plasticization process of the eccentric rotor extruder.In this paper,through the development of an experimental prototype of a split-type uniaxial eccentric rotor that is easy to disassemble,a rapid cooling disassembly experiment was carried out to study the melt plasticization process of materials under different polyolefin materials and different process conditions.The morphological evolution,melt and solid phase distribution during the melting process were analyzed.The results show that the polymer melts and plasticizes in the eccentric rotor extruder through the appearance of a melt film stage,a melt infiltration stage,and a solid suspension stage.In the melt film stage,the material undergoes a melt transfer heat conduction melting process.The material starts to melt from the inner wall of the stator to form a molten film.Under the squeezing effect of the rotor,the core material continuously approaches the heat source,and the melt is forced to penetrate into the particle gap without forming a stable melt layer or molten pool.In the melt infiltration stage,the particles soften and undergo severe compression deformation,which not only increases the heating area of the particles to enhance heat conduction,but also produces a large amount of plastic deformation dissipate heat,thereby speeding up the melting process of the materials.In the solid suspension stage,the viscous heat dissipation of the melt and heat conduction promote the melting of the residual solid.In addition,the experiment measured the processing energy consumption of polyolefin raw material melting and plasticizing in the eccentric rotor extruder by a power instrument.The study found that the mechanical energy consumed by the rotor is the main melting heat source in the plasticizing process of the material.The processing unit consumption decreases with the increase of the rotation speed.Compared with the screw extrusion equipment,the processing unit consumption of the eccentric rotor extruder is reduced by more than 20%.According to the experimental phenomena of the rapid cooling disassembly experiment and analysis of energy consumption of material processing,this paper establishes a melt migration heat conduction model and a particle plastic deformation dissipation melting model,and systematically analyzes the melting plasticization mechanism of the eccentric rotor extruder.The squeezing action of the rotor speeds up the material exchange rate,strengthens the heat conduction,and realizes an efficient heat transfer method for melting,at the same time avoids overheating degradation of the melt.The function relationship of the heating rate of the particles with respect to the amount of deformation and the characteristic size is obtained in particle plastic deformation dissipation melting model.The greater the degree of compression deformation,the greater the rate of particle heating;the smaller the particle size of the raw material,the larger the heating rate,and the faster the melting.The theoretical predictions obtained by the model are in good agreement with the experimental phenomena of the eccentric rotor extruder.In this paper,the method of combining experimental and theoretical research is used to analyze the melt plasticization process and mechanism of polyolefin material by uniaxial eccentric rotor extruder.The research results laid a good foundation for studying the melting theory of eccentric rotor extruder,and provided theoretical guidance for the popularization and application of equipment.