The relationship between electromagnetic absorption properties and cell structure of poly(methyl methacrylate)/multi-walled carbon nanotube composite foams

The understanding of the effect of cell structure on the electromagnetic absorption properties can help to optimize foam structures for different applications. In this research, foams with different air volume percent, spherical and polygonal cell shapes, cell densities in the range of 104-1010 cell/cm(3) and cell sizes ranging from 2.8 to 370.3 mu m are produced using an automatic and controllable supercritical CO2 foaming system. The results showed that foaming of PMMA/MWCNT composites resulted in a 60% reduction in electromagnetic reflection and a 96% increase in specific electromagnetic absorption. The percolation threshold of foams with polygonal cell shape is found to occur at higher MWCNT loading than spherical cell shapes. Electromagnetic reflection is independent of cell density and cell size, while absorption was improved for about 34% with increasing cell density and decreasing cell size, indicating an enhancement of the multiple reflection mechanism. (C) 2016 Elsevier Ltd. All rights reserved.