Jinlong Jiang

The realignment of carbon nanotubes in polymer/CNT composites by mechanical stretching method

A new convenient and simple technique for the realignment of carbon nanotubes in single walled carbon nanotubes (SWNTs) reinforced polymer composites by stretching the semidried matrices in the same direction repeatedly is presented in this paper. Every SWNT in the matrices having an angular displacement tend to align in the stretching direction due to a torque exerting on it. Only when SWNT aligned along the stretching direction, the torque equal zero. CNT/polymer composites SWNT/epoxy resin and SWNT/PMMA were prepared by solution casting and in situ polymerization respectively. SEM demonstrates that SWNTs are well dispersed in the composite matrix and aligning in the stretching direction. The electrical and mechanical tests indicate that the composites prepared by this method present highly anisotropic properties. The mechanical properties of composites rise with the increase of SWNT concentration, composites showed higher mechanical properties such as the Youngs modulus, tensile strength and elongation along the stretched direction than perpendicular to it. A sharp increase of the conductivity value was observed for both SWNT/epoxy and SWNT/PMMA composites just with low SWNT weight fractions. With respect to pure PMMA, the electrical conductivity of 3 wt. % aligned SWNT nanocomposite increased by 9 orders of magnitude, up to 10-3 S/cm.