Synergism in Binary (MWNT, SLG) Nano-carbons in Polymer Nano-composites: A Raman Study

Abstract

ABSTRACTLoad transfer and mechanical strength of reinforced polymers are fundamental to developing advanced composites. This paper demonstrates enhanced load transfer and mechanical strength due to synergistic effects in binary mixtures of nano-carbon/polymer composites. Different compositional mixtures (always 1 wt. % total) of multi-wall carbon nanotubes (MWNTs) and single-layer graphene (SLG) were mixed in polydimethylsiloxane (PDMS), and effects on load transfer and mechanical strength were studied using Raman spectroscopy. Significant shifts in the G-bands were observed both in tension and compression for single as well binary nano-carbon counterparts in polymer composites. Small amounts of MWNT0.1 dispersed in SLG0.9/PDMS samples (subscripts represents weight percentage) reversed the sign of the Raman wavenumbers from positive to negative values demonstrating reversal of lattice stress. A wavenumber change from 10 cm-1 in compression (-10% strain) to 10 cm-1 in tension (50% strain), and an increase in elastic modulus of ∼103% was observed for MWNT0.1SLG0.9/PDMS with applied uniaxial tension. Presence of MWNTs in the matrix reduced the segmental polymeric chain length and provided limited extensibility to the chains. This in turn eliminated compressive deformation of SLG and significantly enhanced load transfer and mechanical strength of composites in tension. The orientation order of MWNT with application of uniaxial tensile strain directly affected the shift in Raman wavenumbers (2D band and G-band) and load transfer. It is observed that the cooperative behavior of binary nano-carbons in polymer composites resulted in enhanced load transfer and mechanical strength. Such binary compositions could be fundamental to developing advanced composites.