The Research Of Influence Of Heterogeneous Nucleation Agents On The Foaming Morphology Of Polyetherimide

Polyetherimide(PEI) is one of the most important high-performance engineering thermoplastics; they have been extensively used in commercial applications because of their excellent properties. In order to broaden the application in the field of engineering, reduces the density of PEI is one of the most important method. Microcellular foam reduces the weight of polymer matrix by generate massive evenly distributed micrometer bubbles, and does not influence the mechanical property. In this article using the supercritical fluid microcellular foaming technology, by addition of different types of nucleation agent. The nucleation mechanism of different shape of nucleation agents and foaming conditions to prepare neat PEI and nucleation agent/PEI nanocellular foams were analyzed according to the factors which influence the stability of bubbles, which include sc CO2 diffusivity and solubility, surface tension and viscoelasticity of polymer.In this article, a series of microcellular and nanocellular carboxylated multi-walled carbon nanotube(MWCNT-COOH)/PEI foams were prepared by the batch foaming method. The results show that the aspect ratio influence the nucleation efficiency and dispersion, and found that m-MWCNT-COOH shows excellent cell morphology with cell size of 180 nm and cell density of 1.58×1013 cells/cm3?Besides, the introduction of polyhedral oligomeric silsesquioxane(POSS) particles which act as heterogeneous nucleation agent were applied to improve the cellular morphology of nanocellular PEI foams. Firstly, the effect of POSS on sorption behaviour and diffusivity of CO2 in POSS/PEI matrix is discussed in order that we can understand if POSS/PEI interface can enrich in CO2. The results shows that the loading of POSS particles increase the solubility and diffusivity characteristics of gases in nanocomposite sheets by changing the distribution of the free volume and enlarging the unoccupied volume in polymer matrix. Then, we show the solid-state batch foaming of samples initially saturated at various pressures. Finally, the characterizations of cellular morphology of POSS/PEI nanofoam and calculation for radius of the critical nucleus(r*) are presented. In a proper foaming conditions, the addition of 0.5 wt% POSS to PEI makes the small aggregated POSS particles approximate to twice radius of the critical nucleus about 13.42 nm, which shows excellent cell morphology with cell size of 66 nm and cell density of 3.34×1015 cells/cm3?...