Sep 02 2017

Handheld plasma treatment for surface preparation or bonding

How does it work?

Short version: it seems like magic but the plasma is chemically modifying that top few layers – putting on high energy groups allowing for the adhesive or paint to form a chemical bond.

handheld-plasmaFirst off, what is plasma? Plasma is ionized gas, which is highly reactive. The handheld plasma treatment system (shown in picture) will deliver this highly reactive gas directed to your materials. The plasma will do multiple things simultaneously as you hover this tool across your substrate: 1) clean the surface free of organic contamination, 2) the reactive atoms will insert itself onto the top molecular layers of your surface, and 3) also etch the top molecular layers very slowly.

Yes, that is someone’s hand on the pistol grip handle and it is quite safe to use when you are that close to the plasma. The wheels allow the user to freely guide on a large (relatively flat) surface while maintaining consistent distance between plasma exit and substrate. In between the two wheels, you see a bright strip. That is the plasma glow discharge (it gives off light when it goes from excited state back down to neutral state). The distance and the speed at which you guide the tool will matter and is highly dependent on the material.

How does plasma do those three things happen and how can you tell?

When you do hover the tool over your substrate, you will not see any physical changes (as you would sanding or grit blasting). Remember, this is happening to the top layers, which is very thin and is not visible to the naked eye.

Organic contamination consists of hydrogens and carbons. Our plasma will usually be used with oxygen based plasma – meaning it will generate very reactive oxygen atoms. When the oxygen combines with 2 hydrogens, it will form water. However, the amount is so small that it volatilizes from the surface. Carbon contaminants will form carbon dioxide, which is a gas form so that flies off the surface.

The material does get etched very slowly because the reactive oxygen atoms are not selective. If you provide enough time and enough reactive oxygen, it will etch through almost anything. So damage to the part is not a concern with our atmospheric plasma technology.

Once the part has been treated, there will be no visual change. The quickest way to tell is by dipping it in water (water break free test) or putting a droplet of water down on the area that has been plasma’ed and compare to another droplet of same/similar size down. This is the quickest and most qualitative way to demonstrate that your surface has been plasma cleaned/treated. What you should expect to see is the water droplet sheath out much further on the cleaned surface compared to untreated. Water is a polar molecule and is attracted to other polar components, thus spreading out more on the oxygenated surface.

Now, if you want quantitative data, then I would recommend a cost-effective portable goniometer such as the Kruss Mobile Surface Analyzer (MSA). The MSA can be utilized in a lab setting or on the production floor. It takes a total 3-5 seconds to do the following: place two droplets (water or another liquid), take contact angle measurements, and the software to calculate the polar and dispersive components of the surface free energy.

Don’t hesitate to reach out if you have any questions.

Richie Woo
Sales Engineer
(626) 410-8491

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