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Chemical Polishing of Lexan

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  • Chemical Polishing of Lexan

    A while ago Evan did a very interesting post on Chemical polishing of Lexan. I tried the technique today with limited success. Evan do you have any example of the before? The after was very nice. I am thinking what I started with was too rough.

  • #2
    I'll check my photos. You need to have a saturated vapour in the chamber so that it actually condenses on the plastic. That means having enough to fill the chamber as it vaporizes. Using some carefully applied heat on the bottom of the chamber works especially well. A curling iron is nice and safe. A regulated soldering iron will work too.

    BTW, I was needing to polish something a few days ago and fetched the can of MC. It was empty, not a trace left. It was the orginal metal gallon container with the cap screwed on tight. It had maybe half a cup left in it when I last used and then sealed it. That stuff is incredibly volatile. It also indicates that it is a very good idea to store it out of the house, which I did.
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    • #3
      I know that precise information on chemical polishing of polycarbonate was once available in one of the Lexan engineering guides at GE. Unfortunately, since Sabic bought out GE plastics, most of the technical guides have been watered down or are in limbo waiting to be re-released without GE logos in them.

      I was previously able to get a reasonably good version of one of the other fabrication guides by writing to somebody at Sabic in the Netherlands so it's probably worth a try. I just sent a request to my contact at Sabic and I'll see if she finds the real engineering guide that tells how to do chemical polishing and a lot of other useful stuff instead of the watered down version now posted.

      --Cameron

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      • #4
        Evan,
        I did mine in two Pyrex pie plates, one inverted. I used a paint stripper gun to generate the heat. I saw the MC boiling so I know it was into vapour. I tried 3 passes but it still looked poor.
        http://i560.photobucket.com/albums/s...olishing_2.jpg
        As you can see it did melt around the nuts I had it set on.

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        • #5
          I see. First, it won't get rid of burrs or really distinct ridges or tooling marks. The starting finish needs to be pretty clean and if you have marks like I see on your pieces they need to by wet sanded first. Second, it is over cooked. If it doesn't clear up on the first pass it won't on subsequent passes. There is one thing you can do that may rescue the part if it is small and that is to dunk it in the MC just long enough to cover it and then quickly pull it out and shake off the excess immediately. Then let it dry for at least an hour to harden it.

          I looked in my archive but that is usually a losing proposition as I have about 20 gigs of photos and over 3000 on line.

          However, a good example of a good starting finish is this item which was not chemically polished but was wet sanded on some parts.

          Free software for calculating bolt circles and similar: Click Here

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          • #6
            Thanks Evan,
            I figured it it did not work first time I had nothing to loose. :-)
            It was a test piece that I rescued once due to a tool height issue. I will try again. I was not really happy with the surface finish in the first place. I will work on that.

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            • #7
              Sorry to thread mine but..

              Originally posted by Evan View Post
              I see. First, it won't get rid of burrs or really distinct ridges or tooling marks. The starting finish needs to be pretty clean and if you have marks like I see on your pieces they need to by wet sanded first. Second, it is over cooked. If it doesn't clear up on the first pass it won't on subsequent passes. There is one thing you can do that may rescue the part if it is small and that is to dunk it in the MC just long enough to cover it and then quickly pull it out and shake off the excess immediately. Then let it dry for at least an hour to harden it.

              I looked in my archive but that is usually a losing proposition as I have about 20 gigs of photos and over 3000 on line.

              However, a good example of a good starting finish is this item which was not chemically polished but was wet sanded on some parts.

              Is there anywhere you have info on the machine you posted in this as a reference? It looks like something a roommate and I were trying to devise a few years back. Came across it accidentally while searching for chemical polishing of lexan.

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              • #8
                This is going back some years to when I was in the injection molding business but I also seem to recall you can polish up polycarbonate with an oxy-hydrogen flame. Lightly play it over the cut or scratched surfaces and it will shine up nicely (basically a light melt job).

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                • #9
                  Yup,

                  That method will work, but its easy to overdo it and get some bubbles on the faces you're trying to polish. We used some methalyne chloride to glass out a part a few minutes ago. Basically boil the mc at around 40C and suspend the piece over the vapors for a few seconds. Glassed out perfectly.

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                  • #10
                    Hello DF Miller,
                    I use to work in the semi conductor field and we were able to use polycarbonate and a oxy acetalene flame but when you use Lexan it is not the same material if I remember correctly it had a special coating that didn't alow the flame to polish the poly. Also it was very important that we had a good smooth edge so we would run the pieces through the wood jointer to get the smooth edge then flame polish.
                    Good luck and get some pic's we want to see what your building.

                    Mr fixit for the family
                    Chris

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                    • #11
                      Chris,
                      My discussion with Evan was five years ago. ;-)

                      I was trying to improve the surface finish on some CNC'd polycarbonate. As Evan pointed out you can only polish out so much. I tried the MC and it worked to a point.

                      It was not just a edge it was a 2.5D machining job.
                      Thanks for your ideas.
                      Dave

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