Research Of HIPS Microcellular Injection Molding Process And Numerical Simulation

Microcellular injection molding is a new technology of combining the microcellular process and injection molding technology,which could reduce product weight under the premise of ensuring performance.It has been widely applied because of its advantages such as the ability of molding complex shaped products.High impact polystyrene(HIPS)is widely used as a kind of engineering plastics.For HIPS Microcellular Injection molding technology,studies on the bubble formation process,the morphology and the properties of the products could promote the application and development of microcellular foam injection molding technology and have important theoretical and practical significance.The influence of HIPS microcellular foam injection molding process parameters on the morphology and mechanical properties of products was studied experimentally and numerically.The paper revealed the bubble formation procedure,determined the influence degree of process parameters on the morphology and obtained the effects of gas injection time and gas injection delay time on the morphology and mechanical properties of the samples and the impact of tensile temperature on tensile properties of foaming specimens.The main research work is as follows:Based on Autodesk Moldflow Synergy 2016,a HIPS/SCF(N2)microcellular injection molding CAE model was established to analyze the filling,packing and warping stages,and changes of the bubble morphology during microcellular injection molding was also studied.In addition,considering the reasonable distribution of different mold cavities,limiting effect of the material flow balance on the foaming process was analyzed,which provides guidance for the experimental study.Using the average bubble radius as studying objective,the orthogonal experiment was designed to investigate the influence degree of process parameters on the average bubble radius by means of signal to noise ratio analysis and variance analysis methods.The amount of gas injection directly affects the bubble nucleation,growth,merging and distribution when product molding and significantly influences on morphology and properties of foaming products.Therefore,the principle of gas injection was studied and the parameters that may influence the morphology during gas injection were analyzed firstly.The effect of gas injection time on the morphology and mechanical properties of foaming products was studied by making use of the microcellular injection molding equipment developed by our laboratory.The results showed that gas injection time has a significant impact on the morphology and cell forming process and the changes of the thickness and the bubble structure have an effect on the mechanical properties of the products.The effect of gas injection delay time on the morphology and mechanical properties of foaming products was studied.The results showed that gas injection delay time affects the gas injection speed by changing the gas injection interval,then affects the morphology and finally affects the mechanical properties.Compared with non-foaming samples by using the universal tensile testing machine with high and low temperature control system,the tensile property of HIPS microcellular injection molding samples at high temperature was studied.The difference of the tensile property between foaming and non-foaming samples was analyzed under different temperatures,which can provide directions for the use of the foam products and the tensile properties data under different temperatures.