Detrended Fluctuation Analysis of UV Degradation in a Polyurethane Coating.

摘要

Changes in the intrinsic structure of paint surfaces resulting from extended UV exposure can significantly alter the appearance of the paint due to a breakdown in the resin that binds the fine paint particulates. In this study, the coating structure of a solvent-based polyurethane was analyzed to establish correlations between the intrinsic spatial scaling properties of the coating and UV exposure time, Atomic force microscopy (AFM) and laser scanning confocal microscopy (LSCM) were employed to map surface structures over a range of scales from 100 nm to 100 square m. The roughness of the polyurethane surface was characterized in terms of scaling exponents by quantifying the local roughness using detrended fluctuation analysis (DFA) to identify long-range power-law correlations and correct for inhomogeneities in the surface structure. This approach provides a means to directly compare AFM and LSCM results over a range of scales consistent with those of a self-affine fractal. The time-dependent dynamics of the roughening process was also determined in order to provide a metric for characterizing the evolving surface morphology. The results provide fresh insight into the mechanisms of polyurethane coating degradation under UV exposure.