Segregation and crosslinking in urea formaldehyde/epoxy resins: a study byhigh-resolution XPS

The segregation of minor components such as flow agents, in an industrial c oil coating based on epoxy resins crosslinked with a urea formaldehyde resi n and applied to a hot-dipped galvanized steel (HDGS) substrate, has been i nvestigated by high resolution XPS. The addition of a low amount of flow ag ent in the coating formulation leads to changes in the surface elemental co mposition. High-resolution monochromated XPS Cls spectra can be peak-fitted taking into account all functionalities of the respective components of th e formulation. The examination of both the elemental and chemical surface c ompositions clearly demonstrates that the use of flow agent in the process leads to its preferential segregation towards the air-film interface. This result is interpreted in terms of minimisation of the surface free energy o f the final coil coating. It is also possible to monitor the extent of cros slinking undergone within the coil coating system, using the peak-fitting i n the same manner as above, and it was concluded that the system is fully c rosslinked. (C) 2001 Elsevier Science B.V. All rights reserved.