Development and Thermal Properties of Carbon Nanotube-Polymer Composites

Abstract

The favorable conductive properties of carbon nanotubes (CNTs) offer opportunities for constructing CNT-based nanocomposites with improved thermal conduction for a range of potential applications. Such lightweight composite materials are expected to have thermal properties that depend on their CNT volume fraction and operating temperature. The construction of CNT-based nanocomposites is challenged by the available processing methods for CNTs that are compatible with the construction of multi-laminated composite structures. The overall goal of this effort is to develop enhanced thermal properties in carbon nanotube-polymer composites that can replace traditional aerospace metallic materials to reduce the weight in space structures. The key innovation of this dissertation is in dispersing the carbon nanotubes onto a prepreg composite structure that sustains thermal storage and increase the thermal transport to support scientific instrumentation to more effectively radiate heat from a composite structure while increasing the thermal properties. The employed structures consisted of individual plies of IM7 prepreg composite with an embedded 8552 epoxy that were each coated with a CNT layer and then combined into the final composite structure using a vacuum-based hand layup technique for curing the 8552 epoxy. The composites were investigated by Raman spectroscopy, thermogravimetric analysis, thermal diffusivity, and differential scanning calorimetry. With varying the concentration of SWCNT up to 30 wt% to the IM7 prepreg composite, its heat capacity sustained over the tested temperature range and its through-thickness thermal diffusivity increased by 30% vs. the virgin composite material. By modeling, such additions of randomly oriented SWCNTs are suggested to increase the in-plane thermal conductivity by 120 to 150% over the temperature range of 120 to 470 K and by 30% in the through-thickness direction. A possible explanation of these improvements in the thermal conductivities are the reductions of the interfacial resistances between the SWCNTs, the 8552 epoxy, and the IM7 composite. The developed methods provide the opportunity for enhancing the thermal properties of a composite through the use of CNTs as additives. Such improvements would be particularly useful in aerospace applications for solar arrays, fairings, and thermal radiators.