Depression in glass transition temperature of multiwalled carbon nanotubes reinforced polycarbonate composites: effect of functionalization

Abstract

Functionalized multiwalled carbon nanotubes (a-MWCNTs) and non-functionalized MWCNTs were melt mixed with polycarbonate polymer by utilizing twin screw micro compounder having a back flow channel to obtain nanocomposites with varying composition from 0.5 to 10 wt% MWCNT and 2 wt% a-MWCNT. Mechanical properties of composite samples were studied using dynamic mechanical analyzer, flexural and tensile tests. Both DMA and flexural and tensile tests suggest formation of continuous network of CNT-polymer that is supported by measured storage modulus for different loading of MWCNT and a-MWCNT. The composite sample showed lower glass transition temperature (T_g) as compared to pure PC. Effect of functionalization of MWCNTs on T_g of its of polycarbonate composites is studied and showed higher T_g depression in functionalized MWCNTs compared to non functionalized MWCNTs based composites over pure polycarbonate. In DMA, lowering of height of tan delta peak indicates that polymer in composite material participating in T_g was reduced along with loading of MWCNT, consistent with immobilization of polymer material present at the CNT interface. Effect of functionalization on morphology was investigated using scanning electron microscope and confirms the better interaction in case of a-MWCNTs compare to MWCNTs based composites. Further, Raman spectroscopic analysis indicates higher interaction between a-MWCNT and PC matrix as compared to as synthesized MWCNT.