Characterization And Regulation Of The Injection Foaming Process Of The Polymer

At present,the research on polymer foaming process at home and abroad is mainly based on mathematical simulation,final cell structure and characterization analysis of self-made visualization system.However,the conclusion has some limitations,because it can't reflect the whole process of the nucleation and growth of the cell in the actual injection foaming process truly and accurately.In order to realize dynamic observation and characterization of injection molding foaming process,it is impossible to use the traditional injection molding experimental equipment.For this reason,referring to the accumulated experience in the design of visualization device at home and abroad,we designed and processed a set of experimental apparatus which could satisfy our online observation of the cell and the growth process of the melt in the thickness direction of the actual injection molding foaming process-the injection molding visualization device in this paper.The dynamic observation of polymer chemical injection could be realized by the device.The differences of foaming behavior in injection molding foaming process under different conditions were studied in depth to find valuable internal laws and realize the control of foaming process.The specific conclusions are as follows:1.We could dynamically observe the formation and growth of cell in the melt in the direction of transparent sample thickness through the self-designed visual experimental apparatus for injection molding.The results showed that the foams experienced three stages?owe foaming,equilibrium foaming and over foaming?in the actual chemical foaming process.The diameter of the pore grew rapidly first and then grew slowly until the diameter remained unchanged.2.As could be seen from the video screenshots of dynamic observation,the foaming process of cell in injection molding was a rapid process.The number of cell and the growth curve of cell diameter were not in line with the linear increase,but they had the common rules with the dynamic research on the nucleation and growth process of cell at home and abroad.It was observed that the nucleation of the pore was not primary nucleation and there were secondary nucleation in the foaming process.The extrusion between cells could cause the morphology of the cell to deform to different degrees,but there was no parallel cell,penetration and wall rupture,which directly proved that the morphology of the cell could remain intact no matter what force was exerted on them in the actual foaming process.3.By injection molding visualization experiment device of the direction of the thickness of the polymer melt inside cell nucleation and growth process of online observation,therefore further study foaming agent content,injection pressure and delay time on the actual injection foaming hole in the process of cell nucleation and growth.The results showed that the increase of foaming agent content and injection pressure could increase the slope of the number of cell and decrease the diameter of cell.The time when the number of cell reached the stable value was advanced.With the increase of foaming agent content,the growth rate of cell diameter decreased,while the growth rate of cell diameter increased with the increase of injection pressure,and the resistance of cell growth increased at the same time.The increase of delay time could significantly inhibit the formation of cell and the growth of cell diameter in the melt in the direction of thickness,and the decreasing trend of the number of cell conformed to the decreasing form of exponential function.The rate of decline was directly related to the total number of initial cell.4.The nucleating effect of nucleating agent in the process of injection foaming was observed dynamically.The results showed that the nucleating agent could increase the nucleation rate and decrease the growth rate of the cell diameter.At the same time,no matter what kind of nucleating agent could advance the time of the maximum value of the cell nucleation.The BC the maximum value of the slope,the formation of cell number,most was about seven times the PP component,and KN-520E was about 6.5 times of PP.With the addition of nucleating agent,many"satellite cell"appeared inside the melt during the foaming process.5.On the premise of the same number of nucleating sites,the structure-activity relationship between the structure of nucleating agent and its nucleating performance was studied.The results showed that the energy reduction of the nuclear barrier was mainly influenced by the interface energy between the gas formed by the cell and the melt.Through the visual observation of the original data and mathematical model fitting analysis,the relative value of?G of BC was 17,which was the lowest group compared with several other nucleating agents or pure PP.It fully showed that BC had the highest nucleation efficiency,which was consistent with the visualization observation results.Mainly because the BC nucleating agent's existing"cavitation"reduced the original gas/melt interface area of the system(A_lg),the BC hollow structure increased the advantage of a lower nucleation barrierA_lg and greatly improved its nucleation efficiency.