Importance of Surface and Interface Characterization

Dr. Amir Hussain, Christa PflugbeilCOMTECH GmbH - Labor für Kunststoffecomtech-labor.de, info@comtech-labor.de

Investigation of Surface – Related Adhesion Failure

Materials and Surfaces

„Materials are indifferent, but the use we make of them is not a matter of indifference.“ (Epictetus 50 - 100 AD)

„GOD made materials but surfaces were the work of the DEVIL“ (Pauli)

Typical Structure of a Substrate Surface

• ContaminationsContaminations ca. 2-4 nmca. 2-4 nmeg. Grease, Wax, Oil, Silicone, Tensideeg. Grease, Wax, Oil, Silicone, Tenside

• Adsorbed LayersAdsorbed Layers ca. 0,5-1 nmca. 0,5-1 nmeg. Hydrocarbon, COeg. Hydrocarbon, CO22 , H , H22OO

• Reacted LayersReacted Layers ca. 3-7 nmca. 3-7 nmeg. Me-O, Me-O-Heg. Me-O, Me-O-H

• Bulk MaterialBulk Material

Scope and Limits of Surface Analytical Techniques

Technique Sensitivity Depth QuantificationMolecular Structure

FTIR > 1000 ppm > 100 ppm Indirectvery good

ESCA 1000 ppm 1-5 nm direct good

TOFSIMS < 0.1 ppm < 1 nm Indirectvery good

Lubricants / Contaminations detected on failed coating at the steel-FBE-interface

• Silocones (PDMS)

• Stearates / Fat

• Stearmide

Typical Contaminations on a Disbonded Interface (sample A) detected by ToFSIMS

Typical Contaminations on a Disbonded Interface (sample A) detected by ToFSIMS

Surface Contamination

• Surface Contamination is the most dangerous enemy of surface engeneering

• A controlled (pretreated) surface is more important than a perfect clean one

• Surface Analysis is the most effectice weapon against this enemy

Main Causes of Adhesive Failure in protective Coatings

• 65% Surface / Interface

• 20% Applications

• 15% Materials