Fabrication of High Content Carbon Nanotube–Polyurethane Sheets with Tailorable Properties

Abstract

We have fabricated carbon nanotube (CNT)-polyurethane (TPU) sheets via a one-step filtration method that uses a TPU solvent/nonsolvent combination. This solution method allows for control of the composition and processing conditions, significantly reducing both the filtration time and the need for large volumes of solvent to debundle the CNTs. Through an appropriate selection of the solvents and tuning the solvent/nonsolvent ratio, it is possible to enhance the interaction between the CNTs and the polymer chains in solution and improve the CNT exfoliation in the nanocomposites. The composition of the nanocomposites, which defines the characteristics of the material and its mechanical properties, can be precisely controlled. The highest improvements in tensile properties were achieved at a CNT:TPU weight ratio around 35:65 with a Young's modulus of 1270 MPa, stress at 50% strain of 35 MPa, and strength of 41 MPa, corresponding to ∼10-fold improvement in modulus and ∼7-fold improvement in stress at 50% strain, while maintaining a high failure strain. At the same composition, CNTs with higher aspect ratio produce nanocomposites with greater improvements (e.g., strength of 99 MPa). Electrical conductivity also shows a maximum near the same composition, where it can exceed the values achieved for the pristine nanotube buckypaper. The trend in mechanical and electrical properties was understood in terms of the CNT-TPU interfacial interactions and morphological changes occurring in the nanocomposite sheets as a function of increasing the TPU content. The availability of such a simple method and the understanding of the structure-property relationships are expected to be broadly applicable in the nanocomposites field.

A review of the interfacial characteristics of polymer nanocomposites containing carbon nanotubes

“…22 The outstanding potential of carbon nanotubes as reinforcement for polymers has been realized. [265][266][267][268][269][270] The mechanical properties of polymer composite materials can be signicantly improved by using carbon nanotubes as a ller. Carbon nanotubes have been widely utilized as a ller to reinforce both thermoset polymers [271][272][273][274] and thermoplastic polymers.…”

Preparation, thermal and mechanical properties of poly (ether‐imide) composite reinforced with carbon nanotube buckypaper

“…25 The BP is a macroscopic paper-like material composed of continuous entangled CNT networks with a highly porous structure, in which, the CNT are free-standing in random direction. [25][26][27] In general, BP is easily fabricated by vacuum filtration from a welldispersed CNT suspension, in which CNT are cohesively bonded by van der Waals interactions. In addition, the thickness of the film can be controlled by either varying the filtration time or the concentration of the CNT prepared suspension.…”

“…The BP is a macroscopic paper‐like material composed of continuous entangled CNT networks with a highly porous structure, in which, the CNT are free‐standing in random direction . In general, BP is easily fabricated by vacuum filtration from a well‐dispersed CNT suspension, in which CNT are cohesively bonded by van der Waals interactions.…”

Disassembly Study of Ultrasonically Welded Thermoplastic Composite Joints via Resistance Heating

“…MWCNT loading ratios equal to 15 wt.%, 20 wt.%, and 25 wt.% were purchased from Cheap Tubes Inc (Brattleboro, VT, USA). Those specific ratios were selected based on preliminary Joule heating experiments, previous work demonstrating suitability for ultrasonic welding [ 36 , 37 ] and literature on high content CNT-based polymer films for sensing, self-heating and resistance welding [ 38 , 39 , 44 , 45 ].…”