Chemical Structure Formation and Morphology in Ultrathin Polyurethane Films on Metals

Chemical Structure Formation and Morphology in Ultrathin Polyurethane Films on Metals 

The performance and long-term stability of adhesive joints and coatings are strongly affected by the chemical and stractural properties of the interphase region situated between the uninfluenced adhesive polymer bulk and the adherend [1-16]. Unfortunately, this interphase is often hidden to the experimentalist, e.g., in closed joints. However, the interphase can be elucidated to a good approximation by studying thin polymer films [16-20] which are often referred to as open joints . Film thickness is varied in this approach to obtain information on microstructure gradients (e.g., in Refs. [1, 3, 4, 19, 20]). Bulk properties are expected to 

Adhesion - Current Research and Application. WulfF Possart Copyright 2005 WILEY-VCH Verlag GmbH Co. KGaA, Weinheim ISBN 3-527-31263-3 

Such differences can result from a chemical or catalytic influence of the substrate, or from preferential adsorption and immobilization of adhesive components on the substrate, or the substrate could even initiate phase separation, crystallization, or any other preferential molecular arrangement. The spatial constraint due to the polymer-substrate and polymer-atmosphere interfaces could alter the molecular mobility and diffusion of species significantly as well - not only for ultrathin Ims but also for closed joints. How all these alterations to the microscopic processes affect the emerging macromolecular structure in a curing polymer adhesive is widely unknown, but there is much empirical evidence that they result in modified technical properties. 

Therefore, selected spectroscopic and microscopic techniques are applied to the characterization of chemical structure formation and morphology in thin polyurethane (PU) layers on Au, Al, and Cu Infrared spectroscopy offers convenient access to the integral chemical properties of thin-fihn and bulk-like polymer samples, while optical (OM) and scanning force microscopy (SFM) allow detailed insights into homogeneity and topology. 

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C. Wehlack, W. Possart, Chemical structure formation and morphology in ultrathin polyurethane films on metals, Proc. oral pres., 7th European Adhesion Conference EURADH 2004, Freiburg im Breisgau, September 5-9, 2004. 

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