Diy PMMA coating

ok, this forum is pretty dead and i cant even remember when i last logged in but anyways here i am after a long time.
so basically i found a way to coat any magnet in ordinary pmma plastic,
the coating is thin, even, smooth, shiny and strong.
i will try to post pictures of a smm tin magnet that i recently coated in pmma, i will also try to make somekind of how to tutorial of this.

Comments

  • pmma has amongst the highest permeability ratings i know. meaning your magnet will be exposed to moisture and might start rusting/decomposing on the long run.
    PMMA would be an okay candidate to protect the body from the implant as it is reasonably bioinert. But PMMA does a pretty poor job at protecting the implant from the body. If you want to go this way i'd suggest extra protection for your magnet. A complete and flawless metal shell would work best. There are a number of plastics which might be more or less suited too.
    The by far lowest permeability ratings go to polytrifluoro chloroethylene. It keeps the moisture out 32000 times more effective than pmma. (Read as in you need 32000 times less thickness for the coating to have the same property)
    Polyvinylidene chloride (PVDC , not to confuse with regular PVC )is another excellent material (used in the original saran wrap) and works 6400 times better than pmma.
    Good ol Teflon dials in for a factor of 900. HDPE makes it to 500 and Teflon's little brother FEP still gets you 250.

    I'd suggest you look into PVDC as it keeps moisture and oxygen out even in very thin layers. This will help to prevent your magnet from breakdown and oxydation. iirc it's even available as a water based sollution to paint on. not sure if this also applies to medical-grade stuff but i think it's used for offshore and automotive protection.

  • I think pmma is an interesting meterial to try if it is relatively simple to coat with without having specialized equipment if you were to say use it as a final coating on top of a smm with an extra layer of gold plating to help fill any pin holes in the TiN.

  • metal platings are very different from a solid and flawless metal shell. if you can't make a plating perfect there is not much reason to do it in first place. a tiny flawed spot is enough to make the whole thing fail. given the past track records filling holes with metal plating seems to be a questionable tactic at least. also think about the bonding and required priming for the pmma to properly adhere.

    anyway, having a way to do reliable pmma coatings would be great. i'll welcome a well documented process/sources/instructions/results.

  • im currently trying a pmma+hdpe blend, it should fix the problems of pure pmma coatings,
    the blend is really dense and doesnt fracture like pmma alone,
    im also trying to coat magnets in pure hdpe for fun,
    the magnet im implanting today is coated in tin and this pmma+hdpe blend. i had to remagnetize the magnet and i got about 95% of the original strenght back.
    for some reason im unable to post any pictures.
  • Im really interested in your results. HDPE has excellent mechanical characteristics and has good biocompatibilty. How are you forming it?
  • Also, how are you remagnetizing? When I've used that method ive had to send them to a service. Did you make a magnetizer?
  • edited January 31
    the method is really simple, i melt the plastic and put the magnet in there. whit my method its hard to get 100% bubble free magnets but i succeed few times anyways. im able to make really thin coatings by first sanding it to size and then using a normal lighter to smoothen it on the magnet.
    as you can read this is only in testing stage but im still able to make really good coatings so this is looking really promising to me,

    and yeah i made a pulse remagnetizer that i put together in 10minutes, 120volts of 44000mf capacitors tru a small coil, works really good since i can get almost the original strenght+must remember the effect of added coating.
    im only testing this method for now but im planning to use normal gold coated magnets in future, gold makes a pin hole free coating so hpde would make perfect protection on top of the gold coating.

    and also sadly im not implanting any magnet because i lost the only one i had for now:/

    this was the first try in coating the magnet whit pmma
    https://imgur.com/a/xcmqDTe
    gotta say im in love whit thermoplastics!
  • edited January 31
    edit: updated link lol
    does the link i posted show a image of the magnet? seems like its not working
  • No. It worked. What agent are you using to crosslink the pmma?
  • i only stirred them together in pretty high heat
  • Melting PMMA isnt really going to work for magnets as it melts at about the same temp as the curie temp. That said, the mixture might. I know that impure hdpe melts at a lower temp so I bet this mix will melt at a lower temp than pmmas normal. Are you checking the temp?
  • pmma melts at 160c, and the high heat hasnt made the magnet unable to be remagnetized, isnt the curie temperature much higher?
  • no i havent checked the temperature at alm
  • keep in mind the demagnetization is also geometry dependent.
    https://www.kjmagnetics.com/blog.asp?p=temperature-and-neodymium-magnets
    getting up to 160°C might be a bit tricky but with a more cylindrical shape rather than a disk you could get away with minor loss in strength.

  • Weird. I looked them up but I don't know what i was reading.. I think you're right.
  • Hey, can you show the layout of your magnetized?
  • sorry ive been really busy lately but i will try to get some pictures of the remagnetizer in this week
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