Multi-scale Simulation Of Morphology Evolution Of Polymer Blends During Filling Stage In Injection Molding

The addition of the second phase to the polymer for blending is a reliable method for improving the properties of the material at low cost and has a wide range of applications in the plastics industry.The injection molding process of polymer blends is a very complex problem of multi-physics multi-scale coupling.It is necessary to both accurately and rapidly simulate the mass transfer,transmission and heat transfer process on the macroscopic scale and to grasp the evolution process of the dispersed phase in the forming process on the mesoscopic scale.The existing injection molding simulation is more mature on the macroscopic scale and has been widely applied in the industry.However,on the mesoscopic scale,the modeling of the multiphase structure evolution in the forming process is still still in the exploratory stage,which needs to be further studied.The problems and difficulties include the modeling and simulation of the evolution of the dispersed phase,the rheological constitutive relation of the polymer blends and the coupling method of the macro mesoscale scale.In view of the existing problems and shortcomings in the multi-scale simulation of injection molding of polymer blends,this paper studies the following aspects from macroscopic and mesoscopic two scales.In this paper,the evolution of the morphology of the dispersed phase in the blends was analyzed by analyzing the characteristics of the polymer blending.The multi-scale simulation of the phase evolution of the filling phase was determined.This paper puts forward the corresponding solutions to the three problems,and establishes the technical route and method framework of this paper.In this paper,based on the lattice Boltzmann method,the evolution of the multiphase structure of the blends under the processing conditions is studied on the mesoscopic scale.The multi-phase model of the single-phase flow simulation is solved by the multi-relaxation scheme and the step-by-step method.The multi-phase model of the polymer blending system is established based on the lattice Boltzmann method of Shan-Chen pseudo-The deformation,rupture,aggregation and deformation of the droplets under the shear process are analyzed,and the mechanism of the evolution of the droplet morphology is analyzed deeply,and the accuracy of the mesoscopic model is verified.In this paper,based on the free-energy format lattice Boltzmann multiphase flow model,this paper establishes a method for modeling the rheological constitutive relationship of polymer blends on macroscopic and mesoscopic scales.Value of the virtual rheometer.Firstly,the relative apparent shear viscosities of the blends under various conditions were simulated for the water-oil blends,and the accuracy and reliability of the virtual rheometers were verified by comparison with the experimental data.And the apparent shear viscosity of the blends on the macroscopic and mesoscopic scales is revealed,and the criteria between the two scales are given quantitatively.Finally,after considering the non-Newtonian rheological properties of the components,the apparent shear viscosity of the polylactic acid / polystyrene blend at the macroscopic scale was calculated,and the results were consistent with the experimental data.The rheological experiments of polymer blends were carried out to establish the rheological constitutive relation on macroscopic scale,which laid the foundation for the coupling of macroscopic flow simulation and mesoscopic evolution simulation.Finally,under the framework of finite volume method for computational fluid dynamics,this paper presents a method to track the trajectories of individual droplets with the flow of motion,thus realizing the simulation of the flow of the filling process on the macroscopic scale of the polymer blending injection molding.Coupling of Simulated Morphological Evolution of Single Dispersed Phase Droplets on View.The results of the simulation not only reveal the stratification of the dispersed liquid droplet morphology along the thickness direction of the product,but also track the morphological evolution of the droplet on the trajectory.By comparing the different forming conditions,it is found that the injection rate is higher than that of the injection The temperature has a more significant effect on the morphology of the dispersed phase droplets,and the result is consistent with the experiment.