Mechanical, electrical and emi shielding response of mwcnt/epoxy nanocomposites

Abstract

The remarkable properties of multiwalled carbon nanotubes (MWCNTs) have sparked much attention in recent years. MWCNT shows extraordinary mechanical, electrical and EMI shielding properties. Therefore, they are widely used in automobile, aerospace and electronics industries. The dispersion of MWCNTs in epoxy matrix enhanced the mechanical strength and toughness of MWCNT/epoxy nanocomposites. However, uniform dispersion and good interfacial interaction of MWCNTs with epoxy matrix is the key issue for preparation of high strength polymer nanocomposites. Therefore, in this work, we use ultrasonic mixing technique for homogenous dispersion of MWCNTs into epoxy matrix to produce high strength polymer nanocomposites. Further, the mechanical characterization has been done by performing tensile strength test and lap shear strength test. The viscoelastic behavior of MWCNT/epoxy nanocomposites were studied by performing Dynamic Mechanical Analysis test. Results revealed that the homogenous dispersion of MWCNTs in epoxy matrix enhanced the tensile strength, toughness, lap shear strength and storage modulus of MWCNT/epoxy nanocomposites. However, adding MWCNT to epoxy matrix not only enhanced the mechanical properties but also its electrical properties, which lead to its use for electronic applications like EMI shielding, supercapacitor electrodes etc. In this work, the electromagnetic interference (EMI) shielding effectiveness (SE) of CNT-epoxy nanocomposites were studied analytically by considering the tunneling effect of carbon nanotubes (CNT) in epoxy matrix. The shielding effectiveness was reported as a function of weight percentage of CNTs and thickness of CNT-epoxy nanocomposites. The tunneling conductivity of CNT-epoxy nanocomposites was measured by considering different parameters such as aspect ratio, interphase thickness and waviness of CNT and their effect with simultaneously change in weight percentage (wt. %) of CNTs. These results concluded that the best conductivity was obtained with MWCNT having a high aspect ratio, thick interphase thickness and small waviness. Moreover, the variation of this conductivity was also simulated to estimate shielding effectiveness of CNT-epoxy nanocomposites. This reflects that a good shielding effectiveness was obtained at a higher concentration of CNT with thicker nanocomposites. It becomes important to know the minimum amount of MWCNT required to achieve the desired EMI shielding effectiveness, as higher MWCNT filler content, after some particular MWCNT content, decreases its strength. Also, determining the electrical conductivity and EMI shielding effectiveness of the nanocomposite experimentally by varying weight percentage, specimen thickness and aspect ratio of CNTs will be time consuming and loss of material, efforts and capital. Hence, we need to analytically model the electrical conductivity and SE of the nanocomposite considering all these critical factors. Later, depending on the required EMI S.E and electrical conductivity, we can control the critical factors to achieve the required characteristics of the nanocomposite.