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How To: Boost the Strength of Plastic Parts

How To: Boost the Strength of Plastic Parts

Many of the plastic parts that make up RC vehicles, especially suspension parts, are made of nylon or a plastic formulation that includes nylon. Nylon is “hygroscopic,” which means it absorbs moisture.  This occurs naturally, as nylon will absorb moisture from the air (and also dry out, when the air is dry). The greater the amount of absorbed water in the plastic, the more flexible (and thus, more durable) it becomes. The natural absorption of moisture occurs over months–unless you speed it up.


Plastic parts made of nylon, or those having nylon in their formulation (such as these RPM arms), can benefit from boiling.

Plastic parts that contain nylon can be boiled to ensure maximum water content and maximum durability. This is not generally necessary for new parts, but there are exceptions. According to Richard Royal of RPM RC Products, the go-to maker of super-tough molded replacement parts, the high pressure (over 7,000 psi) and heat of the injection molding process can create stress inside the part as certain areas cool more quickly than others. Boiling relieves this stress. If you find yourself frequently breaking certain parts, boiling your next replacements before installation might make a difference.

Boiling can can also benefit older vehicles–especially vintage finds that may have spent years getting dryer and more brittle as they baked in attics or garages. Here’s how to boil the toughness back in:


1. Bring a pot of water to a rapid boil. Select a pot that’s large enough to submerge your parts.

Use a strainer to keep the parts off the bottom of the pot.

2. Place your parts into the water. Use a small metal strainer placed inside the bowl to prevent the plastics from sitting on the bottom of the pot, which could lead to melting.



Three minutes is all you need

3. Allow the parts to boil for 3 minutes. Set a timer to remind yourself when the parts are “done.” Boiling the parts longer won’t make them any stronger; once the parts have absorbed all the water they can, extra time in the water makes no difference.


Cool off, dry off, reinstall.

4. Remove the parts and allow to cool. Let the parts cool to room temperature on their own, don’t put them in the fridge or freezer. Once cool, the parts are ready for installation and use.



Beware of cold when running freshly boiled parts


Use caution if you plan to use freshly boiled parts in freezing weather; according to Richard, the moisture inside the arm will freeze, making the part even more brittle than it was before you boiled it.



Boiling will only benefit nylon and nylon blends. Other types of plastics will either be unaffected, or may warp or shrink–not good. When in doubt, boil a broken part first or a scrap of the “tree” (actual term: sprue) the new part came from before boiling a good part. If the material appears unaffected, go for it–boiling the part won’t make it weaker, and will likely make it more flexible and less prone to breakage.



For more tips like this, get The Best of Troubleshooting and The Best of Pit Tips–now available for one low combo price.  Click the image for more info.


Updated: January 31, 2017 — 5:40 PM


Add a Comment
  1. This process is called annealing. It is relieving the internal stress inside the part by allowing the stressed molecular bonds to move where they are ‘pulling’ (stressed) while under heat. The slow cooling is very important. I am unsure of the water part of this explanation, but I do know annealing high stress plastic parts will strengthen them. If the part is molded with low internal stress, annealing will not yield much benefit. Also some plastics require temps as high as 400F for hours, and a very long and gradual cooling period. Research your material, heat in an oven (typical method), and then switch the oven off leaving parts inside with the door closed so the temp will gradually fall over a few hours.

  2. How awesome is that? I kinda heard about this a long time ago and it was effective for some cars not all just don’t use the water to make pasta.

  3. This is great for a back yard basher. This will throw off your suspension alignment while its moving threw up and down motions. Flexibility isn’t what you want for consistant performance for competitive reasons.

  4. What a great cheap trick! My spaghetti will never taste the same.

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