Nanocomposite-enhanced hydrophobicity effect in biosourced polyurethane with low volume fraction of organophilic CNC: towards solvent-absorbent and porous membranes

Abstract

Herein, we focus on the development of new nanocomposite porous membranes based on castor oil-derived polyurethane (PUBCO) and octadecylamine-functionalized cellulose nanocrystals (CNC-ODA) as compatible nanoreinforcements. CNC-ODA was effectively synthesized via a two-step process including oxidation/carboxylation and amidation. CNC-ODA was incorporated at different loading contents (1, 1.5, 2.5, and 5 wt%) in the PUBCO matrix to prepare uniformly dispersed PU/CNC-ODA nanocomposites. FTIR confirmed the formation of strong interfacial interaction between the urethane groups and CNC-ODA functionalities. The TGA and DSC analyses showed that the produced nanocomposites exhibited improved thermal stabilities. Mechanical testing displayed an increase in the elongation at break (100.09% to 135.39%) and a decrease in the Young's modulus (115.89 to 48.67 MPa), which revealed the change in the nature of the nanocomposites towards an elastomeric one. In addition, the contact angle measurement showed an increase in contact angle from 68.9° to 136.9°, giving rise to a highly hydrophobic nanocomposite. Furthermore, the effects of the CNC-ODA content on the morphology, solvent uptake, diffusion and permeability of the produced nanocomposite were also investigated and discussed. The demonstrated findings are propitious for the manufacture of biosourced PU nanocomposite porous membranes with enhanced mechanical, thermal, surface, and solvent absorption performances.