Study On Filling Process Of Polypropylene Microcellular Foaming Injection And Process Optimization

Microcellular foamed products are gradually being widely used in the field of industrial materials because of their advantages in reducing the amount of raw materials and achieving excellent mechanical properties as well as cushioning,sound insulation,heat insulation,high toughness and fatigue resistance.Based on the advantages of microcellular foaming products,it has become a hot research topic in the industry to study its foaming principle,improve its foaming process and shape processing equipment to achieve the design of cell structure and improve product performance.Among them,in the process of microcellular foaming injection,the process of mold filling is affected by the process conditions,and the relationship between melt pressure,temperature and its fluidity is complex.Therefore,it is of great significance to study the process of mold filling in the cavity of microcellular foaming injection.The purpose of this paper was to improve the properties of the products by changing the process parameters to control the process of bubble nucleation,growth and finalizing.The research is mainly divided into four parts:1.Designed the mold structure and installed the cavity pressure sensor,used the cavity pressure data acquisition system to get the pressure drop and its rate relationship at different positions,and got the control range of the pressure drop and its rate under the change of process parameters.2.The quantitative relationship between microcellular structure and pressure drop and its rate was obtained through the statistics of the product's section morphology and foam structure,which laid a foundation for the optimization design of microcellular foaming process and product mold.The weight loss ratio of the products was analyzed,and the significant influence of each factor on the weight loss ratio and the range of regulation were obtained.The results of bending strength and impact strength analysis showed that improving the microstructure and weight reduction ratio can effectively improve the bending strength and impact strength of products.By analyzed the surface quality of the products,the effects of various factors on the surface foaming state of the products were obtained.3.On the basis of the experimental data,a good analysis process was established by simulating the cavity filling process with Moldex3D,and the influence of various parameter changes on the fluidity of melt filling process was studied,as well as the prediction and analysis of bubble nucleation,growth and finalization.The results showed that the simulation results were consistent with the experiment.Through the simulation results,the regularity of bubble size and bubble density can be accurately analyzed,and the relationship between the microstructure of products and the flow performance can be established.4.According to the DOE analysis Moldex3D simulation results under different parameters,used the design expert module to optimize surface and got all the parameters on the products weight loss ratio,bubble average diameter,bubble density,the transfer function of shear stress.A good experimental scheme was obtained through the significance analysis of each parameter and surface optimization.