Biosourced graphitic nanoparticle loaded hyperbranched polyurethane composites – application as multifunctional high-performance coatings

Abstract

The present work reports the development of a novel nitrogen rich hyperbranched polyurethane-urea nanocomposite using bio-sourced graphitic nanoparticles as an effective filler. Initially, a nitrogen rich hyperbranched polyol is obtained by a two step polycondensation reaction between castor oil derived sebacic acid and triethanolamine. The formation of the hyperbranched polyol was confirmed by using various spectroscopic techniques like FTIR, ¹H NMR, ¹³C NMR and ESI-MS. The resulting hyperbranched polyol with 80% degree of branching was further reacted with carboxyl terminated graphitic nanoparticles in different weight percentages (0, 0.1 and 0.5% with respect to polyol weight) along with a diisocyanate (maintaining an OH : NCO ratio of 1 : 1.2) in order to get polyurethane-urea graphitic nanoparticle hybrid nanocomposites. The results suggest that the incorporation of graphitic nanoparticles improves the thermo-mechanical properties, hydrophobic nature, and bacterial and corrosion resistance of the polyurethane nanocomposite. It is seen that a minuscule incorporation of 0.5% graphitic nanoparticles into the polyurethane matrix improves the storage modulus from 365 to 996 MPa, the glass transition temperature from 67 °C to 95 °C, the water contact angle from 50° to 80° and reduces the corrosion rate from 9.2 × 10⁻³ to 5.29 × 10⁻⁵ mm per year in comparison with neat polyurethane. All these improvements in properties are accredited to the covalent linkage, geometry and uniform distribution of graphitic nanoparticles with the polyurethane matrix. In addition, all the polyurethane hybrids show good stability against various bacterial stains.