Role of Dispersion and Functionalization on Mechanical Properties in Carbon Nanotube-Polymer Composites

Abstract

Carbon nanotubes (CNTs) exhibit excellent mechanical and thermal properties. Designing composites that employ CNTs as the reinforcing or filler material offer the potential to create bulk materials with greatly enhanced mechanical and thermal properties. Unfortunately, the resulting property enhancement in CNT, and other carbon nanomaterial, enhanced composites vary greatly. In macroscale composites, like carbon fiber/epoxy composites, the large interface area and relatively low surface area to volume ratio of the carbon fiber/epoxy results in excellent transfer of load or thermal energy across the interface, thus allowing the carbon fiber to enhance the mechanical or thermal properties of the composite. In nanocomposites, the high surface area to volume ratio between the reinforcing and matrix materials requires tightly coupled interactions at the interface. Additionally, due to the high surface area to volume ratio of the nanomaterial filler, there is added difficulty in ensuring the reinforcing materials are uniformly dispersed. These two major differences between macroscale and nanoscale composites results in the existing predictive models failing to predict the effective composite properties. To improve the understanding of the roles that interface bonding and the dispersion of the reinforcing material play on the effective properties, we present the results of a detailed experimental study. To study the role of the reinforcing material/matrix interface bonding, we fabricate CNT/polymer composites where the CNTs are functionalized with different functional groups. To study the role of the nanoparticle filler dispersion, we fabricate CNT polymer composites with different dispersing techniques. This work shows that CNT dispersion is critical for fabricating CNT composites with enhanced mechanical properties.