To improve the situation, researchers in the US have come up with a way of infiltrating buckypaper with polymer solution to create thermoplastic composites that are stiffer, tougher and more suitable for a manufacturing environment.
The work is being led by Ben Wang and his team at Florida State University's High-Performance Materials Institute with input from experts at Lockheed Martin.
"One of the major challenges associated with the resin infiltration approach is the difficulty in controlling the amount of resin being impregnated and the final thickness of the resin-impregnated buckypaper," Young-Bin Park, a former member of the group who is now based at Ulsan National Institute of Science and Technology, Korea, told nanotechweb.org. "Resin infiltration is a multi-step process that involves a number of parameters including resin viscosity, impregnation temperature and pressure, residence time, and drying and baking conditions."
Looking at its composite samples in detail, the team was excited to observe full impregnation of buckypapers with polycarbonate resin, but at the same time the SEM images also revealed the presence of excess resin layers of various thicknesses. The knock-on effect of this is an inconsistency in the mechanical and electrical properties from sample to sample despite similar CNT content across the batch.
To address the issue, Wang's group is now busy characterizing the mechanical and electrical properties of composite sheets formed under various conditions as part of a systematic parametric study.
"Both experimental and statistical approaches are being employed to identify dominant process parameters and formulate their relations to target properties. One interesting topic under investigation is chemical functionalization and surface modification of carbon nanotubes to enhance their dispersion in the aqueous medium prior to buckypaper fabrication and to improve nanotube-resin interfacial bonding after resin infiltration," explained Park. "The interaction between the resin and nanotubes is of critical importance as it dictates the degree of resin impregnation. Therefore, molecular dynamics simulation will be a useful tool for gaining a scientific understanding of this aspect and for providing insights on how the process can be optimized."
The researchers presented their work in Nanotechnology.