4. Conclusions

Generally, EMI shielding is defined as the prevention of the propagation of EM waves from one region to another by using shield materials. With the development of electronic industry, weight reduction is an additional technical requirement besides the good EMI shielding performance. Metal as a traditional EMI shielding material has been replacing with lighter materials, such as polymer-based composites, foams and aerogels. This chapter reviewed various types of lightweight materials with their EMI SEs corresponding to their EMI shielding mechanisms. To verify the benefits of using lightweight materials for EMI shielding applications, a comprehensive comparison was performed as shown in Figure 11. All the data in Figure 11 were collected from the

Figure 11. Comparison of EMI SEs of lightweight materials as a function of density of materials.

Lightweight Electromagnetic Interference Shielding Materials and Their Mechanisms DOI: http://dx.doi.org/10.5772/intechopen.82270

reference papers listed in this chapter. Although the data are not involved all the published results, they are representative to the library of lightweight EMI shielding materials. The reported EMI SEs of polymer-based composites containing conductive fillers varied in the range of 20–60 dB corresponding to the densities higher than 0.8 g/ cm3 . Polymer-based foams reinforced with additional conductive fillers and carbon foams outperform polymer-based composites in terms of EMI SE. They possessed comparable EMI SE of 20–80 dB with the lower density (<0.8 g/cm3 ). Aerogels with ultralow densities (<100 mg/cm3 ) exhibited high EMI SEs in the same range of polymer- and carbon-based foams, indicating they can be used as an ideal potential lightweight EMI shielding materials though the mechanical properties of aerogels still remain a big issue.
