A methodology for developing complex multifunctional materials that consist of or contain polymer/ carbon-nanotube composites has been conceived. As used here, “multifunctional” signifies having additional and/or enhanced physical properties that polymers or polymer- matrix composites would not ordinarily be expected to have. Such properties include useful amounts of electrical conductivity, increased thermal conductivity, and/or increased strength. In the present methodology, these properties are imparted to a given composite through the choice and processing of its polymeric and CNT constituents.
The methodology involves utilization of CNTs in any or all of several ways:
- Coating the CNTs to impart desired properties — for example, coating them with electrically and/or thermally conductive polymers, which could be dissolved in solvents;
- Incorporating uncoated or coated CNTs into a polymeric matrix, possibly in such a manner as to improve the properties of the CNTs, the matrix, and/or the resulting composite; and/or
- Using a polymer/CNT composite as the matrix ingredient of a complex composite that includes any of a variety of other fibrous reinforcing materials.
The figure is a simplified illustration of an example of such a complex composite. In this case, a fabric made of coated ultra-high- molecular-weight polyethylene (UHMWPE) fibers is embedded in a matrix that is, itself, a composite of CNTs in an epoxy matrix. Typically, heretofore, such a composite would be designed and fabricated to obtain high strength, would not contain CNTs, and would be electrically insulating and, to some extent, thermally insulating. By incorporating a suitable quantity of CNTs, one can obtain enough electrical conductivity to drain off excess static electricity to prevent static discharge or to render the composite effective as a barrier against electromagnetic interference, and to obtain usefully large degrees of thermal conductivity and thermal stability, all without sacrificing mechanical strength.