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Why is treatment such a poor indicator of surface quality?
January 7, 2008
First, it is just one potential measure and cannot therefore give a complete picture of the surface. It is a primary measure in that it tells us of the wetability only, not the potential strength of the surface which is what determines the ability to form a strong interfacial bond. Indeed in some early work in the 1960s by Schonhorn1 to establish the source of strong bonding, he would bombard the surface of a polyethylene film with high energy Argon ions. This treatment would cross link the surface of the film, strengthening it such that strong bonds were developed without changing the wetability of the surface (it remained untreated). Schonhorn called the process Crosslinking by Activated Species of INert Gases – CASING. The crosslinking of the surface took place in the amorphous rejoins of the surface.
The film surface was so strong that it could not be dissolved, indicating it was highly crosslinked, even while the bulk of the film dissolved. From this work comes the understanding that a strong interface is necessary for a strong bond to form. Wetting can be important in that it aids in the contact between the surface and the adherent but is not sufficient for adhesion. In some instances, treatment can induce some crosslinking which will improve the surface while it oxidizes it but this will be polymer dependent.
1. H. Schonhorn and R. H. Hansen, “Surface Treatment of Polymers for Adhesive Bonding”, J. Appl. Polym. Sci., Vol 11, (1967), pp 1461-1474
Posted by Eldridge M. Mount on January 7, 2008 | Comments (0)