Influence of Surface Roughness

The benefits of abrasion don’t stop at simply removing contamination. A rough surface for bonding often leads to stronger bonds for several reasons:
 

• Roughness imparts additional surface area with which the adhesive can make contact when forming a bond
• A rough surface provides additional mechanical interlocking at the interface
• Irregularities on the surface may mitigate crack propagation, enabling stronger, more fatigue-resistant bonds

Roughness, especially excessive roughness, may not always be a benefit, however. In order to bond to a rough surface, it is necessary for the adhesive to flow into the cracks and crevices created by abrasion. This is true for both liquid adhesives and tapes. Tapes DO flow! If the adhesive is not capable of flowing, there is less overall contact between adhesive and surface, and trapped air may result in reduced strength or bonds poorly protected from environmental exposure.