The corona treatment (electron bombardment) system is, in principle, very simple. Just create some AC at about 30 kHz and 5 kV(rms), between a "ground plate" and a wire or tube hanging a millimeter or two on the top of the ground plate. Place the plastic on the ground plate and sweep with the tube or wire electrode. You can see the violet glow between the plastic and your electrode.
What I have been struggling with, is that I want to create a simple-to-build, cheap, safe and small system, so that I could make some kind of DIY instructions for everyone to follow. My biggest issue has been finding a source for the transformer needed. I built my own, but it is relatively difficult! It took many attempts to get it working, and then some part of my electronics failed after just a few successful treatments.
Now, the transformers used in microwave ovens do not get to high enough frequencies (the one I tested was fine up to 1 kHz or so; something around 30 kHz would be desirable), and the voltage is a tad low, too (3 kV as opposed to around 5 kV that I found optimum). Those small flyback transformers used in CRT monitors would be fine if they didn't have a rectifier diode built-in, impossible to remove; hence, they give DC, whereas AC is needed.
There are also safety issues that need to be sorted out very carefully.
Otherwise (i.e., when you have the equipment), the corona treatment is a VERY simple and quick process - you "sub" any raw polyester sheet, available just everywhere, in a matter of 30 seconds by sweeping it a few times with this equipment prior to coating. Then you coat within a day or so.
Many other plastics can/must be corona treated, too. It's a widely used process in industry for printing and gluing plastics. Older "flame treatment" is an alternative but probably harder to control.
Those "subbed" polyester roll/sheet products are just corona treated at the factory and then coated with a layer that allows the emulsion to adhere, as the mere corona treatment wouldn't sustain its properties for long enough. But I could make just perfect coatings on raw polyester when freshly corona treated; there was no need for any subbing layer.
Last edited by hrst; 05-09-2012 at 06:29 PM. Click to view previous post history.