Functionalized polybutadiene diol based hydrophobic, water dispersible polyurethane nanocomposites: Role of organo-clay structure

In this article, we report preparation and studies of water dispersible polyurethane (WDPU) nano-composite which has high hydrophobic characteristics with contact angle greater than 100 degrees and strong thermo-mechanical properties. An in-situ method is developed for synthesizing the WDPU nano-composites where hydroxyl terminated polybutadiene (HTPB) functionalized at the terminal carbon atoms with dinitrobenzene (DNB), named as HTPB-DNB, is the diol source for the polyurethane chain, two types of organically modified clays namely Cloisite-30B and dimethyl sulfoxide (DMSO) intercalated Kaolinite (OKao) are the nanofillers and an ionic diol co-monomer e.g. dimethylol propionic acid (DMPA) is used to incorporate the ionic characteristics in the polymer chain to ensure the water dispersibility of the resulting nanocomposites. Microscopy and light scattering studies prove the formation particles of 100-200 nm size, and the particles size and the polydispersity of WDPU nanocomposites vary as the loading and type of clay are altered. In depth analysis of 13C CP-MAS NMR spectra using full width half maxima (FWHM) of carbonyl carbon peak of PU chains reveals the interactions between the polyurethane and organoclay that helped in preparing stable WDPU nanocomposites. Structural analysis of nanocomposites reveal the formation of intercalated morphology till 3 wt% loading of Closite-30B and exfoliated structure for higher loading whereas aggregated structure in case of OKao nanocomposites. Thermo-mechanical and tensile behaviour of resulting nanocomposites are largely influenced by the clay type and loading which can be attributed as the consequence of the different morphology and structure of nanocomposites. The surface hydrophobicity of nanocomposite films is determined by measuring the contact angle which increases with increasing clay loading and all samples show contact angle greater than 100 degrees attributing good hydrophobic surface of nanocomposites. (C) 2016 Elsevier Ltd. All rights reserved.