Multiwalled carbon nanotubes/castor‐oil–based waterborne polyurethane nanocomposite prepared using a solvent‐free method

Abstract

In this article, castor‐oil–based emulsifier was prepared by the esterification reaction between castor oil and maleic anhydride in the solvent‐free and catalyst‐free conditions, and the emulsifier was used to fabricate the multiwalled carbon nanotubes/castor‐oil–based waterborne polyurethane (WPU) nanocomposite in the absence of solvent. The structure of castor‐oil–based emulsifier was characterized by Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy, and the thermal properties, mechanical properties, hydrophobicity and morphology of pure WPU and nanocomposite films with different content of multi‐walled carbon nanotubes were investigated. The result showed that due to interaction between polymer matrix and multiwalled carbon nanotubes, the tensile strength was improved and thermal stability of polyurethane films was enhanced from 223°C to 248°C with multiwalled carbon nanotubes loading up to 0.5 wt%. In addition, because of lower surface energy and higher roughness of materials, water contact angle of polyurethane films was increased from 69.1° to 86.9°. However, when the content of multiwalled carbon nanotubes of nanocomposite was 0.5 wt%, the elongation at break decreases. The reason was attributed to the fact that the agglomeration of nanoparticles was observed in the scanning electron microscope image with multiwalled carbon nanotubes loading up to 0.5 wt%, which destroyed structure of the polymer.