Achieve high performance microwave shielding in poly(ε-caprolactone)/multi-wall carbon nanotube composites via balancing absorption in conductive domains and multiple scattering at interfaces

In this work, multiple interfaces for scattering electromagnetic waves were constructed in the poly(epsilon-caprolactone)/multi-wall carbon nanotube composites (PCLNT) by adding microscale glass beads (mu-GB). The high-performance microwave attenuation of the PCLNT/mu-GB composites was found to be dependent on the microwave absorption in conductive domains and the multiple scattering at interfaces. The multiple scattering was enhanced by increasing the content of mu-GBs. However, the conductive domains were separated by adding more mu-GBs, which led to reduce the absorption. Therefore, the electromagnetic interference (EMI) shielding effectiveness (SE) of the samples increased by adding low mu-GB loadings and decreased by adding high mu-GBs loadings. Fortunately, the absorption of microwaves was enhanced by increasing the conductivity (MWCNT loading) in the conductive domains, which compensated the reduction from decreasing thickness of the conductive domains among mu-GBs. The EMI SE of the PCLNT/mu-GB composites with 50 wt% mu-GBs enhanced from similar to 34 to similar to 44 dB by increasing MWCNT loadings in PCL phase from 3.0 to 6.0 wt%. Therefore, the PCLNT/mu-GB composites with high-performance microwave shielding property could be achieved by balancing the absorption in conductive domains among mu-GBs and the multiple scattering at interfaces.