PDMS/MWCNT nanocomposites as capacitive pressure sensor and electromagnetic interference shielding materials

摘要

Flexible polymer nanocomposites using polydimethylsiloxane (PDMS) and multiwalled carbon nanotube (MWCNT) are gaining importance in the field of electronics as sensor, electromagnetic interference (EMI) shielding, antenna and other materials in devices. PDMS/MWCNT nanocomposite is gaining high demand because of its flexibility, stability and sensitivity than the conventional electronic materials. In the present study, PDMS/MWCNT nanocomposites were developed at different concentrations of MWCNT (1, 2, 4, 5 and 6 wt%), and curing system with help of polymer mixer, and two roll mixing to achieve uniform distribution of nanoparticles inside the polymer matrix followed by high shear force (5 Ton) at 160 °C for 6 min was applied to prepare nanocom-posite sheets with optimum mechanical properties. The surface and bulk mor-phology of PDMS polymer nanocomposites have been observed through scanning electron microscopy (SEM) and transmission electron microscopy (TEM), respectively, to confirm the smooth dispersion of MWCNT nanoparti-cles. In this article, we proposed PDMS/MWCNT nanocomposite-based capacitive pressure sensor with applied pressure ranging from 10 to 100 N. With increase in MWCNT concentration and applied pressure, the current, capaci-tance, and dc conductivity of PDMS nanocomposite increases exponentially due to decrease in mean free path for the flow of electron. However, the increase in conductivity and capacitance depend upon MWCNT concentration and the rate of change in properties increases slowly at higher nanofiller loading. This shows the percolation limit of MWCNT concentration (i.e., at 4 wt%) in PDMS matrix. In addition to this EMI shielding effectiveness (EMI-SE) of PDMS/MWCNT nanocomposites have been measured in X-band frequency range 8-12 GHz. As the MWCNT concentration increases, the nanofiller tends to form a continuous conductive phase, enhances the conductivity network and form an array of close packed networks which makes PDMS nanocomposite more effective in shield-ing of electromagnetic waves. The study also reports that EMI-SE of PDMS/MWCNT nanocomposite increases with thickness of the sample. At 4 wt% MWCNT concentration, a good shielding effectiveness of minimum 35 dB was attained for different thickness (3, 5, 7 mm) sample and the SE increased up to a value of ~ 86 dB.