Characterisation of the curing temperature effects on polyester systems by angle-resolved XPS (ARXPS)

The influence of peak metal temperature (PMT) applied to crosslinkable industrial coil coatings has been investigated by angle-resolved XPS (ARXPS). Two series of coatings based on different reactive polyester resins (linear or branched) but the same hexa-methoxy-methyl melamine crosslinking agent were involved. The formulations also contained either a poly(acrylic) or a silicone-based flow agent additive respectively. The coatings were cured to different extents (seriously undercured, just undercured, properly cured and overcured, respectively). ARXPS demonstrated minor modifications in the chemical composition of the surfaces of these paints as the PMT (and hence cure) was varied, for a given take-off angle of analysis. However, characterisation of the elemental composition at different take-off angles allowed the determination of an elemental depth profile for each coating. These elemental depth profiles clearly demonstrate a preferential segregation of the flow agent additive towards the air–coating surface. The thickness of flow agent outerlayer was evaluated in the range of 1.0–1.5 nm depending on the nature of the flow agent added in the formulation.