Thermomechanical and Free-Volume Properties of Polyester–Polyol Films for Coatings Applications: Role of Diol Composition AITranslate

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DOI：https://doi.org/10.1021/acsapm.9b00502

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Because of their utility in diverse coatings applications, a model series of polyester–polyol films possessing different diol formulations and cross-linked with an aliphatic isocyanate cross-linker under two different conditions is systematically investigated to elucidate the effects of backbone chemistry and cure temperature on the ultimate thermomechanical and free-volume properties. The diol of particular interest in this study is 2,2,4,4-tetramethyl-1,3-cyclobutanediol (TMCD). The glass transition temperature of the films, as measured by thermal calorimetry and dynamic mechanical analysis, is observed to correlate strongly with TMCD content. In the limit of 100 wt % TMCD diol, the operable temperature range for these films increases by as much as ∼60 °C. Surface mechanical properties, interrogated by nanoindentation, also depend sensitively on both TMCD content and cure conditions, and a previously reported phenomenon known as “pileup” is considered to explain some of our observations. Results from positron annihilation lifetime spectroscopy indicate that the nanoscopic free volume of films containing varying levels of TMCD is strongly dependent on chemical makeup but not on cure conditions.