Study On Dynamic Characteristics Of Disk-type Elongation Rheometer

The measurement of polymer rheological properties can not only provide basic data for material selection,formulation and processing design,but also provide a reliable quantitative basis for optimizing die structure and improving molding equipment.The advantages of energy saving,consumption reduction,good dispersion and mixing effect,wide adaptability to materials,and high mass and heat transfer efficiency of elongation rheology in polymer molding processing have led to domestic and foreign scholars' processing of polymer elongation rheology plasticization.The research boom of methods and equipment has made people's demand for the measurement of the material's elongation rheological properties more and more urgent.However,there is still a lack of extensive rheological measurement technology that can be widely promoted and applied.Based on this,the team of Professor Qu Jinping of South China University of Technology designed and developed the first generation of disk-type elongation rheometer,which is used to measure and characterize the elongation rheological properties of polymers.Based on the original elongation rheometer,this paper optimizes part of the structure and adds a feed plasticizing device,improves the neutralization of the extrusion mechanism,and improves the uniformity of the material plasticization and the exhaust effect.This paper discusses the measurement principle and structure of a new generation of elongation rheometer,establishes the dynamic model of the transmission system of the disc-type elongation rheometer,and analyzes the effects of the motor's rotational inertia and the speed ratio of the reducer on the system stability.It is found that the motor's rotational inertia or the speed reducer's speed ratio is too large,which will cause the inertia of the piston to be too large when pressing the piston,which will affect the stability of the system.This paper carried out a series of experiments to explore the influence of different process parameters on the driving torque of the screw and the pressure on the piston.The research results show that: the lower the melt index of the experimental material,the greater the driving torque of the screw and the pressure on the piston;increasing the experimental temperature,the driving torque of the screw and the pressure on the piston are reduced;increasing the maximum speed of the motor,the driving torque of the screw and the pressure on the piston are increased.In addition,this paper uses MATLAB/Simulink software to simulate and analyze the variation law of displacement,velocity and acceleration characteristics of the rheometer transmission system under different process parameters,and draws the following conclusions: under the same process conditions,increasing the experimental temperature will cause the dynamic curve of the transmission system to fluctuate greatly and the stability of the system will deteriorate.Appropriately increasing the maximum speed of the motor and increasing the equivalent damping of the system will help to obtain a smoother dynamic characteristic curve.Thereby improving the stability of the system.In this paper,the research on the dynamic characteristics of a new generation of disc-type elongation rheological measuring instrument can not only provide a certain theoretical guidance for the measurement of the material's tensile rheological measurement experiment,but also help to improve the reproducibility of the measurement data.Subsequent improvements and optimization of the device structure of the rheometer provide a reliable theoretical basis.