Polyurethane/Silane-Functionalized ZrO₂ Nanocomposite Powder Coatings: Thermal Degradation Kinetics

A polyurethane (PU)-based powder coating reinforced with vinyltrimethoxysilane (VTMS)-functionalized ZrO₂ nanoparticles (V-ZrO₂) for thermal stability was developed. Chemical structure, microstructure and thermal degradation kinetics of the prepared coatings were investigated. The peak of aliphatic C–H vibrating bond in the Fourier transform infrared (FTIR) spectrum of V-ZrO₂ was a signature of VTMS attachment. Scanning electron microscopy (SEM) images reveled that, by increase of V-ZrO₂ content from 0.1 to 0.3 wt.% and then 0.5 wt.%, some agglomerations of nanoparticles are formed in the PU matrix. Thermogravimetric analysis (TGA) of the PU/V-ZrO₂ powder coatings was performed at different heating rates nonisothermally to capture alteration of activation energy (E_a) of degradation of PU/V-ZrO₂ powder coatings as a function of partial mass loss by using Friedman, Kissinger–Akahira-Sunose (KAS), Ozawa–Wall–Flynn (FWO) and modified Coats–Redfern isoconversional approaches. It was observed that by addition of 1 wt.% V-ZrO₂ to PU resin the early state degradation temperature at 5% weight loss increased about 65 °C, suggesting a physical barrier effect limiting the volatility of free radicals and decomposition products. Incorporation of 5 wt.% ZrO₂ led to about 16% and 10% increase in E_a and LnA of blank PU, respectively, which was indicative of higher thermal resistance of nanocomposite powder coatings against thermal degradation. There was also obvious agreement between model outputs and experimental data. The results reveal that nanocomposite coating shows superior thermal properties compared to neat PU powder coatings, and the presence of nano ZrO₂ in sufficient amount causes retardation of the thermal decomposition process.

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Published in: Coatings
License: https://creativecommons.org/licenses/by/4.0/
See article on publisher's website: https://dx.doi.org/10.3390/coatings10040413

The University of Doha for Science and Technology replaced the now-former College of the North Atlantic-Qatar after an Amiri decision in 2022. UDST has become and first national applied University in Qatar; it is also second national University in the country.