High performance vibrational damping poly(urethane) coatings: Blending ‘soft’ macrodiols for improved mechanical stability under weathering

Abstract

Heavily crosslinked Poly(urethanes) (PU) with composed of ether and/or ester macrodiols have been synthesized and subjected to accelerated weathering (i.e., UV-light and water) to assess the effects of the macrodiols on mechanical stability. Data from confocal microscopy, water contact angle analysis, dynamic mechanical analysis, and infrared spectroscopy have been employed to correlate the effects of the macrodiols, their degradation, and the bulk mechanical properties of the PUs. The single component PUs, containing one macrodiol, became mechanically unstable after weathering, where they either became increasingly stiff or weakened to the point of fracture. Surprisingly, the two component PUs, containing both ester and ether macrodiols, exhibited an enhancement in their mechanical stabilities both before and after weathering. We attribute this enhancement to molecular packing considerations and to the types and degrees of degradation during weathering. In addition, overlaps in the UV–vis absorbance spectra indicate that the ester moieties in the ester macrodiol provide a sunscreen-like effect and ‘protect’ the urethane linkages from absorbing the UV-light. Overall, the results reported here demonstrate that minor structural changes in the macrodiol can alter significantly many of the bulk properties of two-component PUs, in which the networks are crosslinked. The results also provide a clear ‘blueprint’ for developing vibrationally damping PUs with specific desired properties for improved mechanical stability during weathering.