Effect of temperature and electron beam irradiation on the dielectric properties and electromagnetic interference shielding effectiveness of ethylene acrylic elastomer/millable polyurethane/SWCNT nanocomposites

Abstract

The blend nanocomposites based on single-walled carbon nanotubes (SWCNT), ethylene acrylic elastomers (AEM) and millable polyurethane (MPU) have been successfully prepared with 0.5 to 5 parts by weight/volume per hundred parts of rubber(phr) of SWCNT loading loading. The sheets prepared by using hydraulic press have been exposed to electron beam (EB) to induce cross-linked networks. The characteristic shifting of CO vibration in the FTIR spectra confirms the formation of hydrogen bonding between the two phases. The SWCNT filler dispersion in blend phase has been analyzed by high-resolution transmission electron microscope (HRTEM). The effect of SWCNT and EB dose on cross-link density, swelling, gel fraction and dielectric properties have been studied. The cross-linked density increases with an increase in radiation doses and SWCNT loading, which is confirmed from Flory-Rehner analysis. The swelling percent of the EB cross-linked nanocomposites decreases with increase in EB dose and SWCNT loading. However, the gel fraction increases with increase in EB dose and SWCNT loading. The dielectric relaxation behavior of the EB-treated nanocomposites has been analyzed in a wide range of frequency (1–106 Hz), temperature (25–120 °C), EB dose (50–400 kGy) and SWCNT loading (0.5–5.0 phr). The increase in temperature and SWCNT loading, the dielectric permittivity (ε′) increases, however with EB dose ε′ exhibits a decreasing behavior. This can be explained on the basis of interfacial polarization of the SWCNT phase in the interface. The blend nanocomposites show an increasing trend of AC conductivity (σac) with the increase in SWCNT loading, EB dose, and temperature which is due to the hopping and tunneling mechanism. The blend nanocomposites show the percolation behavior in the range of 1.46 phr SWCNT with respect to σac value. The real and imaginary parts of the impedance (Z′ and Z′′) have been found to decrease with increase in SWCNT loading. Semicircular nature of the Nyquist plot explains the decrease in bulk resistivity of the systems with SWCNT loading and temperature. The electromagnetic interference shielding effectiveness (EMI SE) of the fabricated conductive nanocomposites has been studied in the frequency range of 2 × 109–8 × 109 Hz and reflection occurring at the surface (SER), absorption of the electromagnetic radiation (SEA) and the total shielding effectiveness (EMI SE) of the external electromagnetic radiation by the developed nanocomposites have been measured. The effect of SWCNT loading, radiation dose and frequency on SER, SEA and EMI SE have been analyzed and SEA and EMI SE are increased with an increase in both SWCNT and radiation dose.