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WEATHERING DEGRADATION OF A POLYURETHANE COATING. (R828081E01)
Citation:
Yang, X. F., C. Vang, D. E. Tallman, G. P. Bierwagen, S. G. Croll, AND S. Rohlik. WEATHERING DEGRADATION OF A POLYURETHANE COATING. (R828081E01). ANALYTICA CHIMICA ACTA. American Chemical Society, Washington, DC, 74(2):341-351, (2001).
Description:
The degradation of polyurethane topcoat over a chromate pigmented epoxy primer was examined by atomic force microscopy (AFM), scanning electronic microscopy (SEM), X-ray photo-electron spectroscopy (XPS) and Fourier transform infra-red spectroscopy (FTIR) after the coated panels were exposed in a QUV chamber. It was found that upon QUV exposure, blisters formed on the topcoat surfaces during the initial phase of coating degradation. As a result of blister formation and subsequent breakage, coating gloss was lost before any pigments were exposed in the coating. XPS and FTIR analysis indicated that urea and urethane group concentrations increased in the coating upon exposure. It is suggested that the build-up of hydrophilic groups in the coating during coating degradation promoted water absorption into the coating system, then the alternating dry and wet environment caused the formation of osmotic cells and thus blisters on the coating surfaces.
Author Keywords: Accelerated weathering test; Polyurethane degradation; AFM; SEM; XPS; FTIR