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Warning! Loctite eats plastic

Posted by Martin Poller on October 28, 2011 at 12:30pm

3689430581?profile=originalMaybe this has been posted before, but I was unaware of this.

I have been assembling my quadcopter and as advised have used red loctite # 271 to lock the metal nuts and the prop mounts.

I have used it all up and bought some blue loctite #243 and have used it on some of the nylon nuts last night and have just noticed today that it has eaten away the part of the nylon bolt inside the nut and the nylon nuts are soft and easily split in two with my thumb nail.

I must hold my hands up and admit that I didn't realise that threadlock could do this to plastic, but thought I would bring it to everybodys attention.

Martinp

 

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Comments

  • Daniel Schinsky February 21, 2015 at 5:30pm

    All this being said.. what should I use? My props are supposed to be self tightening... but only two of them obviously spin against the threads so they do not come off. but the others come off no matter how tighten them.... I unfortunately used blue locktiteand it ruined all four of my props they just spun up and broke apart where the locktite barely touched it.... :(

  • George Shanahan May 10, 2014 at 12:00pm

    Loctite FUMES cause the plastics to become brittle in a fairly short amount of time.  Don't use it anywhere even near any plastic or on a model. Vibra-Tite might be an alternative.  I myself use a tiny drop of Testors acrylic or enamel or acrylic-enamel paints that come in tiny bottles to do the job.  I learned about this in 1980 when I started flying RC helicopters with a group in Lake Charles, LA, so it has always been a problem and apparently Loctite cannot find a solution for this side affect of their product.

  • Martin Poller November 15, 2011 at 10:25am

    Update for all

    On re-examination of the bolts I must confess that the loctite has only actually eaten the polycarbonate bolts and nuts, it doesn't seem to have had the same effect on the nylon ones. I'm still going to keep it well clear of any plastics in the future though. : )

     

  • Hardcore November 14, 2011 at 9:39pm

    I think that before we say that a particular chemical degrades another one, we have to be sure that the chemicals/materials we are testing are actually what they claim to be.

    You would be very surprised at what gets passed off as 'plastic' when you buy parts online, and you would be horrified to learn than some of it may actually be recycled medical waste, such are the horrors to be found in the market that is fasteners, ESP. when they are sourced in  Asia.

     

    A quick check of the Loctite site and the relevant data-sheets make it vey clear exactly what a given product is compatible with and when it should be used. The moral is RTFM, or in this case RTFDS.

     

     

  • Martin Poller November 14, 2011 at 3:36pm

    Thanks all for your individual experiences, I don't feel as much of an idiot now for using it on the nylon bolts, I'm wondering now if I should strip my quad back down and replace all the nylon connectors in the frame or just leave them now as the damage is done. They don't seem to have deteriorated any, but there again it could be quite spectacular if the frame came apart in mid flight!!

     

  • Moderator
    Sgt Ric November 14, 2011 at 2:52pm

    It seems to me that besides the plastic eating theory several people have mentioned, Locktite expands as it dries, with disastrous results for plastic frames, etc.

    Again, a good product for metal on metal, but the moral seems to be, keep away from plastics.

     

    An expensive lesson in my case.

    Turned an R/C Graupner Bell helicopter into a display model.

  • Ben Schwehn November 14, 2011 at 2:11pm

    Just want to add my experience:

    I used locktite (or rather a similar product called Hypo Fix It) on my jdrones frame and it really had a terrible effect not only on the nylon screws (caused them to break and fall off) but more significantly also on the plastic parts of the frame (clanding fins, dome and motor mounts), causing those parts to crack and fail much more easily. I did really not expect this, after all using glue on plastic parts is usually fine.

  • I.S. November 1, 2011 at 3:11am

    @Hardcore: Thanks for the explanation.

  • Hardcore October 31, 2011 at 7:23pm

    yep.....

    They are mainly self locking because when under a  minor torque they stretch , thereby pulling the nut threads into the bolt threads more strongly, the key is that you do not over tighten them so that the "stretch" is made permanent and they fatigue and then fail. A lubricant only really works if the surfaces can move over one another freely, even if you loosen off a nylon nut & bolt they will still self lock to a certain extent if the threads are molded correctly.

    I spent a significant amount of time looking at Nylon, PC &PE when we produced a cheap mechanical plug-in timer that had to run reliably 24/7/365/5

  • I.S. October 31, 2011 at 3:32am

    @Hardcore

    So nylon bolts and nuts are self locking AND self lubricant?
    That sound surprising.

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