Controlling the structure of arborescent carbon nanotube networks for advanced rubber composites

Generally, composite materials are made from two or more constituent materials with different properties. The resulting material exhibits distinct characteristics that are different from the individual materials forming the composite. Over the past few years, production and enhancement of composite materials have significantly attracted the interest of many researchers due to their increased demand for various applications. Unfortunately, the greatest challenge has remained developing efficient techniques to optimize the properties of these composite materials so as to realize their full potential applications.

The advancement in nanotechnology has seen the increasing use of carbon nanotubes as nanofillers material in optimizing properties of composite materials owing to their excellent thermal and mechanical properties. However, carbon nanotubes are susceptible to damages due to poor disentanglement and dispersion processes. This has even further increased the challenging of extracting the carbon nanotubes properties as a filler in composite materials. To this end, researchers have identified isolation of individual carbon nanotubes as an effective method for their dispersion like in the cases of surfactants and polymer wrapping.

In a recently published literature, the inherent properties of long carbon nanotubes have been used to produce composite materials. For instance, arborescent carbon nanotube network has been fabricated by a dispersion approach. It comprises of arborescent agglomerates that are capable of transferring photons, electrons and strains over long distances irrespective of the direction. Unfortunately, little has been reported about controlling the disentanglement state of the carbon nanotubes as well as arborescent agglomerates organization through dispersion which are key considerations in realizing high-performance composite materials.

Recently, scientists at the National Institute of Advanced Industrial Science and Technology in Japan: Dr. Kazufumi Kobashi, Dr. Seisuke Ata, Dr. Takeo Yamada, Dr. Don Futaba and Dr. Kenji Hata significantly improved the performance of carbon nanotubes composite materials by controlling its entanglement state within arborescent agglomeration. They used a wet-jet mill to vary the shear forces applied to the aligned single-walled carbon nanotube in the solution so as to control the disentangled state. Additionally, a carbon nanotube rubber was fabricated. Their research work is published in the research journal, Composites Science and Technology.

From the experimental results, the authors observed that an increase in the jet-mill pressure resulted in a significant change in carbon nanotubes agglomerates from trunk-like structures to mesh-like structures that exhibited high entanglement degree. Consequently, the smaller sizes of the agglomerates increased in number with the increase in pressure. This was attributed to the fact that mesh-like structures were formed by shortening of the carbon nanotubes. Based on these findings, it was found out that fine-tuning of carbon nanotubes agglomerates structures leads to the tremendous increase in the electrical conductivity of the fabricated carbon nanotube-based rubber composite.

The proposed method preserved the quality and length of the carbon nanotubes due to minimal shortening. Additionally, the fine-tuning of the disentangled carbon nanotubes agglomerates structures greatly enhanced the performance of the composite materials. Thus, appropriate jet milling pressure should be selected for effective production of arborescent carbon nanotube agglomerates. Therefore, the study will advance the fabrication of high-performance carbon nanotube composite materials for various applications and research activities.