"DRY PRIMING" a means of applying trace chemicals
to optimise surface
Application Note 12.
DRY PRIMING is a method of chemically conditioning surfaces by rubbing with a virtually dry Trib-Tool and without applying excess wet chemicals. This causes high absorption and gives a measure of control that was not previously possible, permitting surfaces of metal parts to be conditioned during and after machining to improve - wetting, adhesive bonding, coating, cold welding etc.. Although the following explanation focuses on metals, the tools and the process extends to many other materials.
Metal surfaces are considered inorganic emphasising there chemical difference to those of organic polymeric materials like paints, plastics, adhesives or lubricants. These SMART metal surface have organic polymers securely tethered within their inorganic surface oxide layers making them more compatible with organic coatings.
A Trib-Tool is a mildly abrasive tool used to condition a metal by excoriation (scraping clean) and chemically treating at the same time. The conditioning chemical is carried within the tool and is slowly released during rubbing in small but sufficient amounts to form a coating but it appears to be a dry process - hence the name DRY PRIME.
The conditioning chemical usually comprise of tadpole like surface active molecules with electrically charged "heads" which attract and attach to the surface as it is cleaned. The unique aspect of our process is the tadpoles have inorganic heads which readily integrate with the high energy new surface while screening their more vulnerable organic tails, reducing the risk of catalytic attack from a high energy clean metal surface. In theory the organic tail material can be virtually any species of functional organic polymer, chosen to give the surface a desired character. After abrading the natural oxide rapidly reforms upon exposure to atmosphere, trapping the inorganic material deep within, allowing a useful proportion of the tails to be orientated away from the surface, some reaching out beyond the oxide. The organic chain can have either a passive or active terminal to which other chemicals can attach.
With the exception of a few noble metals like gold, all common metals used in engineering such as steel and aluminium are covered with a natural protective oxide. By modifying the oxide it is possible to change the surface character. A common parameter used to describe surfaces is the concept of surface energy. This is a physical property, a thermodynamic quantity, an indication of a surfaces potential to interact with other materials. Practically, surface energy increases as adsorbed layers and oxide is abraded off. But unless screened the new surface instantly interacts with atmospheric oxygen to form a new protective oxide layer. As the oxide reforms so the surface energy falls and the surface becomes progressively less chemically active.
Therefore Surface Energy gives an indication of how a surface will interact with other materials to wet or adhere or bond, or, how it behaves in a rubbing frictional contact. By conditioning a surface with this method its surface energy is adjusted by modifying the oxide layer. Hitherto metals have been chemically conditioned by reacting wet chemicals onto their surfaces - we now show how to integrate the chemicals into the surface oxide and that in essence is why we use the euphemism "SMART" to described these surfaces.
This is something new in manufacturing - its not in the text books yet !
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