Threadlocker and ABS does not mix

Tricopter Tilt mechanism 4NoLoctite2

Warning! Do not use loctite on any parts of the tilt mechanism! ABS and other thermoplastics react with the chemicals in the Loctite. The chemical breaks down the bonds in the ABS, making the part very brittle and weak. Use a tiny amount of CA glue on the screw instead.

Loctite website states this:

Not Recommended For

  • Use in pure oxygen and/or oxygen rich systems and should not be selected as a sealant for chlorine or other strong oxidizing materials
  • Use on plastic parts, particularly thermoplastic materials where stress cracking of the plastic could result

After some testing I noticed that the original Loctite reacts the strongest, breaking down the ABS very quickly and a larger portion of the part is affected. Simply screwing the motor screws into the motor makes the whole top piece explode in to tiny pieces! Off brand threadlockers seems to be hit or miss if they do break down the ABS or not. So I highly recommend not using any kind of threadlock on the tilt mechanism at all, or any ABS parts for that matter.

Thank you Robert for bringing this to my attention

18 thoughts on “Threadlocker and ABS does not mix

  1. Some very good information that I myself was not aware of. Without trying to make more work for you, it might prove valuable to include a small warning note, simply put on a piece of paper with the kits/tilt mechanisms as I’m sure there will be plenty of customers who may not read this. Saves you and them future hassle? Just a thought.

  2. Good to know, I just received my new tilt yesterday. I will use CA when I put it on. Maybe the loctite was a factor in the first one breaking, or maybe it was the flip 😉

    • I was not aware of this (did not read the microscopic warnings on the little blue bottle), so I used genuine blue Locktite when I assembled my tilt mechanism.

      After a few flights I started to get problems in the air. Suddenly the tricopter started to yaw by itself and I was barely able to land it with full counter yaw. I then discovered that the “teeth” of the 3D printed tilt mechanism were destroyed and I had to revert to V2 method for the til. I though I had destroyed the 3D printed by not being careful enough when inserting the servo, but now I know it was the Locktite.

      • Sorry to hear that. I didn’t know it before Robert pointed it out. Did some testing to confirm and was very shocked by how efficiently the loctite destroyed the ABS. The Hobbyking thread lock doesn’t seem to affect it quite in the same way. At least not as quickly. Had one exposed to it for 48h now and it’s still seems to be strong.

        • Don’t worry, David.

          Being a rookie, I thought the servo could become off center due to SW tuning, so I realigned the tilt to what seemed to be correct neutral a couple of times before I understood the correct reason :-p
          I managed to land pretty safely 2 of the times, the 3rd I hit the ground with an angle so that I cut off one of the servo cable when the arm end hit a rock. Sharp edge + rock = good scissors :-p

          Anyway, the servo horn method of your previous tricopter versions is now working good for me.

  3. Sorry this might be a bit long. I was doing some research and this is what I have found so far.

    Blue loctite is a Anaerobic adhesives. “Anaerobic adhesives are generally not used with most plastics. Anaerobic adhesives will stress crack some plastics, including many thermoplastics like ABS and polycarbonate. If the product is used for metal-to-metal but in close proximity to plastic, there is the possibility of excess liquid product or vapor affecting the plastic. In the case of compatible plastics like acetals, the anaerobic adhesives are simply not the best family of products for effectively locking and/or sealing. Often Loctite® Cyanoacrylates (Instant Adhesives) are substituted if they meet the other application parameters.”

    For Anaerobic adhesives to start their curing process they need metal ions. If metal ions are not present curing will no occur.
    ” Unfortunately it would be much more likely to develop a leak path because the adhesive must be in contact with a metal surface to cure; surfaces such as paper, cork or rubber prevent the adhesive from curing. Uncured adhesive remains a liquid and will further degrade the non-metal components and possibly cause blockages or damage.”

    “Leaving uncured liquid CA remaining on some plastic substrate (such as polycarbonate, acrylic, and polysulfone) in a stressed condition may cause the formation of cracks in the plastic. Some remedies for avoiding/minimizing stress cracking are closing the bond joint quickly, use reinforced grades of plastic, anneal parts, or speed cure the CA with accelerator or light (for Flashcure products only).”

    Stress cracking would be a good term for what I saw on the tilt.

    “Chemical stress cracks are typical brittle cracks which occur at or below the tensile strength of the plastic or material. Specifically, the name “chemical stress cracking” is given to the phenomenon where chemical agents adhere to, or come into contact with, areas where tensile stress is present (ie, where the part is being loaded), and where cracking occurs over time as a result of the combined effect of the chemical agent and the stress. The surfaces of this type of crack are smooth, and in certain cases, they may take on a mirrored appearance.

    In terms of growth mechanism, it is said that gaps open between molecules when the part is loaded or in some other condition of stress, that the chemical agent penetrates into these gaps, and that the cohesive power (or strong binding) between the molecules is reduced.

    The exact mechanism has not yet, however, been completely understood. Chemical stress cracks can be prevented from occurring by eliminating either the chemical agent or the stress.”

    So I’m wondering if the hk version of loctite is Cyanoacrylates based since they know its going to be around plastics.

    Also I did find on the loctite site the best thing to do if you get loctite on plastic is to wipe it off immediately and if you have an accelerator use it to flash cure the loctite.

    • Don’t think the HK version is CA based, but I don’t think they use the same active ingredient. The real loctite is a much better product when it comes to actually locking metal to metal :D, but the HK doesn’t seem to react with the plastic, which is nice.

  4. Is there any way to see if my parts have been affected by the treadlock? I used some Jamara stuff, it says its not suited for plastics. I would rather buy a replacement upfront than having it fail mid-air.

  5. Look for threadlock that has not cured, wet spots are where the plastic will be weak. Next look for stress cracks, and finally put the part under load. The minute I put a load on the part it just shattered.

  6. Yeah I put loctite on the spinner of a radian. A week later the whole thing shot off while I was fpv soaring. That was fun.
    So, I knew it was bad for plastic! Yet I went ahead and got a little on my tilt because I assumed David would know this! I thought he knew something about ABS being different than other plastics. See what happens when you assume!!?? Oh well, I ordered a replacement anyway, because I broke mine apart when I hit a tree at high speed. I have it held together with epoxy right now, hope it holds in the meantime. No gopro until I get the replacement!

  7. Yep, mine failed in a crash. I’ve printed a replacement, and am trying to figure out how to keep the screw in place. David recommends a bit of CA, but how do you get the CA in place? How about putting a bit of Loctite inside the servo threads?

  8. Hey David,

    A great way to keep any nut from working loose, is to use teflon tape. You could actually use teflon “dope”, but it is kind of messy, and the tape is much easier to use. The tape needs to be installed in this manner: 1. Lay the tape down so that the working end is facing toward you. 2. Lay the male thread down on top of the tape so that the head of the bolt is to the right. 3. Lift the tape up onto the threads, and hold it in position as you turn the bolt. 4. Do not over wrap, it only takes one or two turns.

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