Preparation of Polyurethane Acrylate Coated Carbon Nanotube Nanocomposites by Emulsion Polymerization.

The aim of this work was to prepare strong and conductive polyurethane acrylate nanocomposites. First, urethane prepolymers with different molecular weights and hydrophilicities were synthetized. Then, their corresponding polyurethane acrylate nanocomposites were prepared by ultrasonically-assisted emulsion polymerization in the presence of various ratios of urethane prepolymers and acrylate monomers. Thermogravimetric analysis (TGA) and tensile results showed that thermal stability and mechanical properties of polyurethane acrylate samples are significantly dependent on the molecular weight and hydrophilicity of the urethane prepolymer as well as the content of acrylate monomers. Polyurethane acrylate sample (i.e., PUAc-2B50) with optimum mechanical properties and thermal stability were chosen as matrix to prepare nanocomposites in the presence of nanotubes grafted with polymerizable acrylate groups (G-MWNTs). Transmission electron microscope (TEM) revealed that the surface of nanotubes is uniformly coated with polymer nanoparticles. The nanocomposites containing 3 wt% G-MWNTs demonstrated a great modulus up to 374 MPa and excellent strength up to 18.74 MPa. Meanwhile, they indicated remarkable high electrical and thermal conductivities; as the electrical conductivity of the nanocomposites increased by more than twelve orders of magnitude, and thermal conductivity reached to 12.5 times of the neat matrix. The developed nanocomposites hold high potential for diverse applications, such as printable electronic devices, nano-sensors, and heat/electrical induced shape memory polymers.