Preparation and characterization of carbon nanotube/polydimethylsiloxane nanocomposites with enhanced O 2 impermeability,dielectric and EMI shielding properties

In this study, composites of hydroxyl-terminated polydimethylsiloxane (PDMS) reinforced with multiwall carbon nanotubes (MWCNTs) were prepared using solution mixing assisted by sonication. The vulcanization behavior of PDMS was investigated using modulated temperature DSC, revealing a decrease in the reaction rate at higher MWCNT loadings. The prepared nanocomposites were characterized for their thermomechanical and dielectric properties, as well as for oxygen permeability and electromagnetic interference shielding effectiveness (EMI SE). Thermogravimetric Analysis (TGA) showed that thermal degradation of the specimens began at lower temperatures and ended at higher temperatures compared to pure PDMS. Enhancements in tensile strength and Young’s modulus were also recorded, particularly at higher filler concentrations. Swelling after immersion in toluene was lower for all MWCNT/PDMS composites compared to pure PDMS. Notably, membranes made from MWCNT/PDMS composites demonstrated a significant decrease in O₂ permeability. Dielectric Relaxation Spectroscopy (DRS) revealed that the percolation threshold was reached at a low CNT content of 0.036 phr. The Electromagnetic interference (EMI) Shielding Effectiveness (SE) of the prepared MWCNT/PDMS membranes -recorded in the X-band- was strongly dependent on the CNTs loading. Membranes with thickness of ∼1.1 mm exhibited SE values of 5 and 17 dB, for loadings of 0.5 and 4.0 phr, respectively. Based on these results, it is concluded that MWCNTs/PDMS composites prepared via solution mixing demonstrate improvement in their performance in many critical properties, even at very low reinforcement levels.