Mechanical and piezo-resistive properties of functionalized multi-walled carbon nanotubes/styrene-ethylene-butadiene-styrene composites

Carbon nanotube, owing to its excellent mechanical and electrical properties, is promising to be used in polymer composites towards both structural and functional applications. In this paper, one type of multi-walled carbon nanotubes (MWNTs)/polystyrene-b-(ethylene-co-butylene)-b-polystyrene (SEBS) composite was fabricated. MWNTs were first surface functionalized with SEBS before blended with polymer matrix. The surface modification of MWNTs was characterized by various techniques including X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy and thermogravimetric analysis (TGA). Results indicated that MAH (maleic anhydride)-g-SEBS was successfully grafted onto MWNTs with grafting ratio 8.7 wt%. The SEBS composites containing functionalized MWNTs exhibited excellent mechanical and electrical properties, evidenced by tensile and electrical properties tests, owing to enhanced interfacial interaction between the SEBS-g-MWNTs and the SEBS matrix. SEBS-g-MWNTs/SEBS was also explored in terms of piezoresistivity. The composites exhibited excellent piezoresistivity after the percolation threshold (1.0 wt%) and good repeatability during multiple cycles. The rubbery behavior coupled with electrical properties make this type of composite promising in advanced soft electronics.