Electric field and current assisted alignment of CNT inside polymer matrix and its effects on electrical and mechanical properties

Abstract

Polymer matrix composites, reinforced with aligned carbon nanotubes (CNT), have a great potential in myriads of applications including flexible electronic and biomedical devices. However, effectively aligning the CNTs inside any matrix has always been a challenge. Present study deals with fabrication of an aligned carbon nanotube reinforced polymer matrix composite and effect of the methods of alignment on anisotropic properties of the composite. Multi-walled carbon nanotubes (MWCNT) reinforced Polyvinylidene fluoride (PVDF) composite with uniform dispersion and alignment of CNTs is fabricated by solution casting technique. CNTs are aligned with the application of alternating voltage as well as pulsed current. The voltage-assisted films have shown good dispersion and alignment of CNTs inside PVDF matrix. On the other hand, the current-assisted alignment led to the formation of shortest, continuous path for the flow of electrons and hence, resulted in formation of highly anisotropic conductive film. Directly current passage assisted alignment of CNTs in the composite film records an impressive 360% improvement in conductivity in the direction parallel to the alignment as compared to the structure with randomly aligned CNT. At the same time, the composite in transverse direction to the alignment was totally insulating, indicating the efficiency of alignment. With the addition of only 0.5 wt% CNTs to PVDF matrix, film shows improvement of elastic modulus and tensile strength by 180% and 150%, respectively, as compared to pure PVDF film. However, the films behaved mostly isotropic in terms of mechanical properties, showing improvement in all the directions with CNT reinforcement. This study provides effective way to align CNT in thermoplastic matrix to tailor the directional electrical conductivity significantly.