Hydrophilic and hydrophobic films based on polyurethane cationomers containing TiO2 nanofiller

Abstract

Polyurethane cationomers thin films containing (0–2 wt%) surface functionalized TiO2 as ecological water dispersions were obtained, and the structure of the cationomers have been confirmed using FTIR and NMR methods. Incorporation of the surface modified TiO2 nanoparticles caused considerable changes in the thermal, mechanical, and surface properties of the PU films. Importantly, films made with MDI isocyanate surface-modified TiO2 were hydrophobic and their free surface energy (FSE) was below 35 mJ/m2, while films containing unmodified TiO2 were hydrophilic with FSE above 48 mJ/m2. SEM observations exhibited uniform dispersion of nanoparticles in PU matrix. The activation energy of the glass transition process was calculated based on multifrequency TOPEM DSC data and the higher activation energy was found for composites with higher content of PU/TiO2 or PU/f-TiO2 due to the stronger hydrogen bonding between soft segment microdomains and hard segments after incorporation of PU/TiO2 or PU/f-TiO2. Good thermal and mechanical properties, which correspond to those of PU elastomers, are promising features for the application of the obtained cationomers as modern coating materials.