Study On The Effect Of Interface On Foaming Of Polyetherimide Microporous Injection Molding

Microcellular material having a smaller cell (microns) size, the larger the cell density compared to conventional foamed material with excellent thermal insulation, sound insulation, light weight, high mechanical properties, high stability, small precision and other characteristics, has great value in the areas of the aerospace, automotive, electronics and defense.The main features of this work focus on the foam of polyetherimide in injection molding process, and studied the important parameters plasticizing stroke, gas content and injection speed of polyetherimide (PEI) and polypropylene (PP) composite foam. Polyetherimide material selection of work mainly as it has good mechanical properties, low smoke, radiation resistance, abrasion resistance, low temperature and superior performance in the field of aerospace and precision devices have gained widespread favor, but study the porous foam material is very small. These excellent properties, combined with the many advantages of microcellular materials, PEI study of porous foam injection molding process can advance its wide range of applications, especially great significance in the field of cutting-edge aerospace, defense and anti-radiation applications.Under certain conditions, the first of the present work was pure PEI foam, and found to have a low nucleation density, with relatively low nucleation limits further increase the efficiency of the cell density. For this shortcoming, in which after adding the talc as nucleating agent, the nucleation density has been significantly improved, indicating increased nucleation ability to obtain high-density cell material from nuclear agents. But the agent dispersed in the matrix easy reunion, limiting cell good distribution.By addition of PP dispersed domains in the PEI matrix by means of strong shear mixing, PP will be spherical in shape with a slight dispersion in the matrix, and the size and distribution of the dispersed phase can be regulated by mixing of the process conditions, to distribution of nucleation sites provide a more flexible regulation. By comparison with the PC, PA66interface features, PP blends with PEI obtained good results, thanks to the PP and PEI larger interfacial tension. The PP and PEI interface provides a number of heterogeneous nucleation sites, which have a lower nucleation barrier, can greatly increase the cell into a nuclear capability. Furthermore PP with a relatively small surface tension in which favor the nucleation of bubbles, reduce the overall resistance of nucleation PEI matrix.In addition, different process parameters on cell morphology had a great impact, directly determines the weight plasticizing stroke, and weight loss have a direct effect on cell morphology, the weight between8wt%to20wt%have access to a better cell morphology. PEI/PP, and the weight reduction of pure PEI showed different responses can be varied and a larger pore density of the foam; the study also found that the gas content of the PEI/PP has a larger solubility of N2obtaining smaller cell size. The injection rate’s effect is higher on the pure PEI. These phenomena indicate that PEI/PP has a very high nucleation density, PP added evolved into nucleation and growth patterns of PEI, from a single nucleation growth into a "Gas storage-with heterogeneous nucleation-quick release gas-PEI bound to live by the formation of cell " this better model.To further improve the dispersibility of the PP, the choice of the force with PEI stronger PPMA, so that small changes in the particle diameter of PP dispersed phase. The dispersed phase and interface become more to the coherent interface with each other with increasing the content of PPMA. At the interface of the phases, gas diffusion and nucleation becomes easy. So that the gas can quickly melt precipitation, the cell growth rate increases, reducing the time to relief increases the retention of gas content in the matrix. PPMA is added to obtain a higher cell density and lower cell size. Studies have shown that the interface for microcellular injection molding PEI foam nucleation and growth sectors all have an important part in promoting.