Effects of mechanical strain on the electric conductivity of multiwalled carbon nanotube (MWCNT)/polyurethane (PU) composites

Conducting polymers have been under development for more than thirty years as replacements for metals in various applications, such as fuel cells, solar cells, actuators, etc. In this study, we investigate conducting polymer composites and attempt to fabricate composite polyurethane/multiwalled carbon nanotubes. The multiwalled carbon nanotubes (MWCNTs) were acid-treated to add functional groups such as -OH or -COOH so they could then be chemically bonded to diisocyanate to form a urethane linkage. Because they have fewer impurities and reduced surface roughness (as confirmed by TEM micrographs), acid-treated MWCNTs can be better dispersed in a polyurethane (PU) matrix than untreated MWCNTs, and acid-treated MWCNTs exhibit better adhesion with the PU matrix, as well. In addition, the conductance test of MWCNT/PU films as a function of elongation showed that the conductance of the acid-treated MWCNT/PU increased up to a certain % elongation, while that of the untreated MWCNT/PU decreased monotonically with % elongation.