Understanding chemical adhesion

Using an adhesion promotor to achieve the desired result can only be successful when fully understanding the surface properties of the system.

To investigate the adhesion, pull-off tests were carried out on UV-curable coatings with and without adhesion promotor. These samples were further analysed. X-ray Photoelectron Spectroscopy (XPS)  is widely used as surface analysis technique, because it can be applied to a broad range of materials and provides valuable quantitative and chemical state information from the surface of the material being studied.

That is why OCAS used XPS to check the suitability of a phosphorus containing adhesion promotor on a UV curable coating system.

Test panels were sampled by pulling off a glued on dolly. Both the dolly interface and the steel substrate were investigated.

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The XPS spectra with adhesion promotor on both dolly (in red) and steel substrate (in green) , clearly confirm the creation of strong phosphorous containing chemical bonds.

In this case, the phosphorus profile intensity could be confirmed by glow discharge optical emission spectroscopy (GDOES). This technique provides rapid, direct bulk or depth profile analysis.

The direct adhesion of this UV-curable coating on bare steel could be established by using a phosphorus containing adhesion promotor, without the need for surface preparation.

“Our state-of-the art surface analysis equipment allows to measure and understand adhesion phenomena. This significantly reduces time and cost of optimising the coating formulation.”

 

Philippe Legros, Senior project leader, Surfaces department, OCAS