Reinforce Brittle Plastics
 

Hi All-

I'm sure many of you have had the pleasure at some point of having a plastic piece snap clean off or in half at some point during your life. While I have found a way to repair these plastics (superglue and baking soda), I was wondering if anyone knows of a way to reinforce plastics that have not broken yet, but are clearly brittle. Is there a paint or something similar one could cover an entire piece with to provide stability, even to those pieces which have not yet broken?

I read in an article that you can soak plastic in warm water for about a day and this will sometimes allow the plastic to absorb some of the water and become more pliable.

-G

Subscribing. I'll be curious to see what answers you get. I restore old cars and starting to get into the 80s, seeing lots more plastics and lots less replacement parts availability. I have quite a few times reinforced the back sides of plastic panels with fiberglass, but that's not possible for everything. I had started experimenting with trying to chemically brighten translucent coolant reservoirs/overflow bottles after seeing some promising results on youtube based on methods developed by people who restore old computers and game consoles (yeah, that's a real thing). You might research that hobby segment too.

You might try painting the piece with POR15 paint It's a flexible urethane type paint that can be applied to plastic. It would need to be top coated since it's not UV resistant. I've read about people using it on those big plastic seat back panels and hardboard panels also. It's expensive, but it also comes in small cans and can be either brushed or sprayed on.

https://hackaday.com/2013/02/05/usin...plastic-parts/

I've never done this, but it seems like a suitable way to reinforce weak knobs and such?

Not on my Jaguar, but on a '70s Mercedes I recently restored I used GRP mat and resin on the hidden side of some of the large, brittle plastic panels (under dash tray, interior panels etc). I did this proactive after using it to repair some cracked panels. Some of the resins 'set' slightly more flexible than others (I think for marine use) - those seem to be best.

After much research, the POR15 paint is a good option; I have yet to test it. On the to do list.

The GRP mat is brilliant! Ideal for the underside of plastics where you have the space. Worked well in a few of my use cases.

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Pieces small enough to fit in a pot can be boiled. This does not make them like new but does improve tolerance at common snap points.

For larger pieces (such as the center console I am working on now) I found leaving it submerged in water for over 24 hours makes me feel like I’ve accomplished something. I have no evidence to show it makes a difference.

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Some pieces with prolonged UV exposure and known plastic composition cannot be saved, such as various windshield defrost vents. The louver style assembly pieces are a notorious example. In my case, I found the grille style replacement to be not only more effective but made of a better plastic. Highly recommended for anyone still using those horrific louver pieces which have either already broken or are on the verge of snapping with the slightest of pressure.

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On other interior pieces, the metal clips which slide over plastic tabs (such as the rear vent assembly to the center console) are a known enemy. If at all possible, depress the tabs on the clips first with a needle nose pliers before removing the part; then remove at the angle in which the clips are aimed for the best chance of survival.

In many cases, this is impossible and it’s not your fault; it wasn’t meant to come apart. If it was a clean snap, the baking soda and super glue method or JBWeld may allow you to reattach. Sometimes you do not need the clip/tab; the piece will stay in place with other clips. Another option is to remove the metal clip from the tab and use gaffers tape (or similar) to thicken the tab enough to hold it in place with pressure. Every situation is different.

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Minor rattles and squeaks can be addressed with adhesive felt as needed.

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As I have taken this car apart and reassembled multiple times over, I continue to find places where its clear different plastics were used, even on the same assemblies; the center console being a perfect example. Your mileage will vary as you explore. The good news is in some cases you can get by missing a clip or two, repairing broken pieces with the superglue/baking soda or JBWeld can be done and there are an abundance of yards with S-Types for your picking pleasure.

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As with any car or truck, take proper care of it and it will take proper care of you. There are endless car care products; I humbly suggest using a name brand UV protectant for your interior plastics, leather and rubber surfaces. (Note these surfaces typically have different products specific for each type)

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Why does a Sony boombox from 30 years ago have thicker and more robust plastic than a 20 year old 50k luxury automobile? I digress. Hope this helps with your driveway dives. Feel free to hit me with any questions, I’ll tell ya what I know as the S-Type journey continues.