Preparation and Rheological Properties of Functionalized Multiwalled Carbon Nanotube/Waterborne Polyurethane Nanocomposites

Abstract

Waterborne polyurethane (WBPU) was synthesized by a polyaddition reaction with toluene diisocyanate (TDI), polytetramethylene ether glycol (PTMEG), dimethylol propionic acid (DMPA), and triethylamine (TEA). Aqueous polyurethane dispersions with three different weight fractions, 30, 40, and 50 wt%, were prepared. All the dispersions made with these concentrations showed Newtonian viscosity behavior. Multiwalled carbon nanotubes (CNTs) were functionalized using a mixture of sulfuric and nitric acid at a ratio of 3:1 and added to these dispersions in two different loads of 0.1 and 0.5 wt%. Ultraviolet visible spectrometry (UV/Vis) spectroscopy proved the formation of stable suspensions following ultrasonic agitation. The rheology of these suspensions was characterized using dynamic and steady-state measurements. The higher amount of CNT in the suspension imparted non-Newtonian and complex viscoelastic behavior. This was attributed to a physical network formed due to the presence of the functionalized CNTs. The Cox-Merz rule was not observed for these suspensions.

Keywords:

• multiwalled carbon nanotubes
• nanocomposites
• rheological properties
• waterborne polyurethanes

Acknowledgment

We gratefully acknowledge for partial financial support from the Research Council of Tehran University. We are also grateful to the Research Institute of Petroleum Industry (RIPI) for providing MWCNT for this project.