Boiling, Thereby Resuscitating Plastic Trim Pieces!

Here's some good repair guides for your Tercel :) Look here for help first!
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ARCHINSTL
Goldie Forever
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My tercel:: Goldie is a 1986 SR5 attualmente con Weber/also owned the first T4WD in STL in late '82
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Boiling, Thereby Resuscitating Plastic Trim Pieces!

Post by ARCHINSTL »

From the new Rock Auto newsletter - this is really neat - does anyone have any experience with the process?
Tired of breaking the old, brittle plastic clips that hold on exterior and interior trim? Worried that the plastic thermostat housing will either leak or crack after being over tightened? Hoping for a way to rejuvenate the yellowed plastic gears, slides and rollers in that window regulator? Having trouble sliding the plastic handles onto the metal rods that came with that new foosball table? The answer to these and other plastics conundrums is an elixir available at the nearest kitchen sink.

My dad was a plastics engineer for 30+ years. One of the best tips he has given me thus far is to rejuvenate and limber up old and new thermoplastic polymers by soaking them for a minute or so in boiling water. The results with nylon can be especially dramatic. Yellowish nylon goes into the water brittle and comes out supple and milky white. New composite thermostat housings, foosball table handles, and other plastic pieces that must be mounted to metal become slightly more flexible and are an easier and better fit.

The boiling water does not melt the plastic. Soaking nylon in room temperature water for a long time has the same impact as a short bath in boiling water. The chemistry is too complex for just the son of a plastics engineer to explain. Basically the moisture releases tension between polymer molecules that was created when the plastic was first made (molded, extruded, etc.) or that built up over time as the plastic was exposed to sunlight, heat, chemicals or otherwise aged.

Over the years I have only seen good results from putting my plastic parts in boiling water. At worst the plastic seems unaffected, probably a thermoset plastic (rigid body parts, distributor caps, Bakelite, etc.). However, there are myriad plastic resin recipes and plastic products out there and I must include a disclaimer and encourage common sense and caution. Do not soak plastic pieces that include electronics, gaskets, lubricants, paint, adhesives, decals, etc. that are not supposed to be exposed to water. Do not bring a plastic part out of a freezing garage and immediately dunk it into a boiling pot of water. Thin, molded plastic pieces like interior trim or milk jugs might lose their shape if exposed to heat. Heat and moisture from boiling water might not be uniformly transferred through very thick plastic pieces. If you are at all concerned about the temperature of boiling water, then maybe instead try soaking the plastic piece in unheated water for a day or two. Don’t boil a greasy composite valve cover in your spouse’s favorite spaghetti kettle…

Tom M.
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My tercel:: 1983 SR5 wagon 4WD stock 3A-C Federal

Re: Boiling, Thereby Resuscitating Plastic Trim Pieces!

Post by smokerx »

I got this stuff from a friend at the car wash called "black tire" for making your tire walls look new. It looks like just 10w 30 motor oil with an applicator sponge. I use it on all my hard plastic trim, tires and any black plastic bits. It restores everything to looking factory new. When doing the trim, tape it off like you're painting it, unless you have clear coat on the paint. It makes sense that the plastic baking in the sun will eventually bake out all the petroleum oils in the rubber and plastic and motor oil will restore it and prolong its life by preventing cracking.

I use either steel wool or barkeepers friend on the chrome plating to bring that back to a shine and I've used old (not black) motor oil to coat a cedar deck. Came out looking like an ocean pier or any deck close to sea water.
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