Effect of pigmentation on polyurethane/polysiloxane hybrid coatings

Abstract

ABSTRACTRutile TiO2 was formulated into polyurethane/polysiloxane hybrid coatings in order to investigate the influence of pigmentation on the inorganic phase of the hybrid coatings. Two urethanes were prepared from the isocyanurate of hexane diisocyanate (HDI), alkoxysilane modified HDI, and tetraethyl orthosilicate (TEOS) oligomers, with oligoesters derived from either cyclohexane diacids (CHDA) and 2‐butyl‐2‐ethyl‐1,3‐propanediol (BEPD) or adipic acid (AA), isophthalic acid (IPA), 1,6‐hexanediol (HD), and trimethylol propane (TMP). The oligoesters were spectroscopically characterized using GPC, FT‐IR, and NMR. Chemical interaction between the TiO2 and the sol–gel precursor was investigated using solid‐state 29Si NMR and XPS. The morphology, mechanical, viscoelastic, thermal properties of the pigmented coatings are evaluated as a function of pigmentation volume concentration (PVC). Using AFM and SEM, the pigment was observed to be well dispersed in the polymer binder. The thermal stability, the tensile modulus, and strength of the coatings were enhanced with increasing PVC, whereas the pull‐off adhesion and flexibility (elongation‐at‐break) were reduced with increasing PVC. Finally, the pigmented coatings were evaluated by electrochemical impedance spectroscopy (EIS) and the results showed that 10 wt % of the pigment improved the corrosion resistance of the entire coating system. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 42947.