The effects of highly structured low density carbon nanotube networks on the thermal degradation behaviour of polysiloxanes

Abstract

Abstract Carbon nanotube-carbon aerogel (CNT-CA) networks are a member of a novel class of ultra-low density, high surface area, hierarchically structured, carbon-based materials possessing unique mechanical and physical properties. Through the secondary incorporation of a polymer matrix into these aerogel systems it is now possible to form intercalated polymeric hybrid CNT-CA composite materials with polymer to carbon surface internal surface contact areas in the order of ∼600 m2 g−1 at carbon loadings as low as ∼1.5 wt %. Reported here is the synthesis of a series of well-defined poly(dimethylsiloxane) (PDMS)/CNT-CA composite systems, their characterization and the in-depth analysis of the effects of the carbon architecture on the thermal stability and degradation behaviour of the of the PDMS matrix. The results of degradative thermal analysis using both pyrolysis gas-chromatography/mass spectrometry (py-GC/MS) and thermogravimetric analysis (TGA), clearly demonstrate that the presence of the CNT-CA scaffold within the PDMS matrix greatly increases the thermal stability of the system and drives the matrix towards calcination at temperatures above 600 °C. Subsequent characterization of the residual materials using a combination of fast magic angle spinning solid-state nuclear magnetic resonance (Fast-MAS NMR), energy dispersive X-ray spectroscopy (EDAX) and electron microscopy have demonstrated that the improvements in thermal stability are concurrent with the relative loading of carbon nanotubes within the aerogel matrix, that the PDMS matrix is being driven towards the formation of increased levels of SiO2 on degradation and that the preferential calcination effect is a function of the unique high surface area fibular network structure of the CNT-CA monoliths.