Plastic Repair: 1973 Dodge radio and air conditioning trim panel

[1970FuryConv]

I have the 1973 Dodge radio and air conditioning trim panel pictured below. It’s in good condition, except for the crack also pictured below. I have some JB Weld Plastic Weld that I was considering using to make the repair. I have read of people using fabric behind repair. 2 questions

· What kind of fabric is used in plastic repair?

· Is JB Weld a good adhesive for this repair or should I use something else?

Thanks for your help!

 

[CBODY67]

The plastic cracks as the oils in it evaporate with time, which can also result in some shrinkage and cracks/breaks. The "fabric" is used to reinforce the plastic used for the repair. Just like in fiberglass repairs, you place "the mat" and then soak it in plastic (which is then worked to make the repair invisible, just as with sheet metal).

Rather than a hard JBWeld-type product, perhaps something like the clear resin (UV light-cured) that another member used to repair his windshield washer reservoir (posted in here a month or so ago)? Use the plastic to put everything back together, then the fabric for reinforcement, then re-install gently?

There are SOME OEM plastics which superglue will NOT stick too, from my experiences. Too much "oil" in the plastic formulation? As others have used a baking soda dust of the pieces before they used superglue, too. Whatever works . . .

Just some thoughts,
CBODY67

 

[bigmoparjeff]

I prefer the two part adhesives that are specifically made for plastic. You can find them at just about any auto parts store in the same area as the epoxy's, in the same type of double tube dispenser. One brand is something like "plastic welder".

Another method that usually works fairly well is to use a soldering iron to melt the plastic back together.

Jeff

 

[65sporty]

I often use a soldering iron like Jeff mentioned, but your only going to want to use it on the back of that panel as to retain the texture on the front. It depends on the type of plastic on how well it works though.

 

[bnz84]

That dash piece will take any number of glues and epoxy. The issue is if you try some thick stuff between the crack you may get it to work but you will still have a glue line. If you dig that off you will mess with the texture. For me I've used super glue, the thicker stuff is better, and it will bond and give you a nice front look. Almost unnoticeable. But super glue is not very super on anything that get torque or twisting. So you have reinforce the back. Mostly I use metal window screen. Before you do rough up the plastic with course grit sandpaper. Cut an L out of the screen for that corner and use something like epoxy, regular or plastic bonding, or more superglue and baking soda. Its my new go-to. Very strong and quick. Epoxies work well too. For that corner I would double the L layer once the first is dry. I have a crack in backup dash bezel like yours and that's how I'm going to do it. Superglue plus more superglue and baking soda. Have fun

 

[luigi164]

I don't know how it looks on the back, but if possible I would fabricate some kind of small square (plastic cut out of anything you could find) and glue that on the backside..

 

[1970FuryConv]

Thanks all! Why does baking soda help superglue?

 

[bnz84]

Thanks all! Why does baking soda help superglue?

In my reading it looks like CA/SG will cure with the addition of moisture in the air. To keep that from happening in the bottle they add acids to keep it liquid. Anything that neutralizes the acid and raises the PH will quicken the curing process. The higher the PH the quicker it hardens. Adding baking soda will immediately harden CA glue and produce heat. The commercial "accelerator" sprays are just some kind of alkaline - could be baking soda - dissolved in water or even etoh. Double whammy of curing power. I bet Tums would work fine! Using some sort of powder, vs liquid, adds a benefit of thicker layer over top the fix. It is sandable, drillable, and paintable but it wont get real smooth. That's why it should be on the back. Something more presentable are smooth epoxies/JB weld. And I think I mentioned in another thread you can completely rebuild a plastic tab that is broken off. Just create a form out of tape and keep adding BS + SG one after another until you get a piece big enough and then sand. I would not have guessed it would hold up to a tightened screw but it does if you over lap the new tab with the original plastic. Again that assumes that one side can be thick and ugly - like my feet.

I used BS+SG today on a plastic seat track cover. The more flexible the plastic the less likely it will stick. I tried using landscape fabric in place of screen because I ran out of screen. Worked well and that stuff is also strong. That's the stuff they make promotional reusable grocery sacks out of. I think the more intelligent term is non-woven polypropylene geotextile. On the other hand I was able bond 2 pieces of 1/8" aluminum together at a 90 deg angle. It wont take a bunch of torque but its surprisingly strong.

 

[1970FuryConv]

In my reading it looks like CA/SG will cure with the addition of moisture in the air. To keep that from happening in the bottle they add acids to keep it liquid. Anything that neutralizes the acid and raises the PH will quicken the curing process. The higher the PH the quicker it hardens. Adding baking soda will immediately harden CA glue and produce heat. The commercial "accelerator" sprays are just some kind of alkaline - could be baking soda - dissolved in water or even etoh. Double whammy of curing power. I bet Tums would work fine! Using some sort of powder, vs liquid, adds a benefit of thicker layer over top the fix.
How much powdered baking soda do you add? It must be a very small amount for a tiny repair.

 

[bnz84]

There is no set amount of BS to add. Not sciency at all. Not like 2 part epoxies. Get a box of baking soda or pour some out into a plate. Any amount greater than a pinch. Add SG to the crack and push both sides together until they bond. Then grab a small pinch of baking soda and dust the back of the plastic where there will be no doubt some SG squeezing out. It will immediately harden rock solid. Blow any loose powder off into the sink or floor. Wipe any liquid from the front off with towel. Front is done. Then on the back again add more SG around the crack that is now a powdery lump. Add screen or fabric to the wet glue as flat as you can. Then another pinch - a bit bigger - of BS on top. Will immediately turn to a bigger lump of hard powder. Repeat until you feel its strong enough. PM me if you have questions and we can call.

 

[1970FuryConv]

I used the crazy glue/baking soda method 5-6 in layers. It works

 

[bnz84]

Isnt it fun pulling it off of your fingers! Pretty sure I have no fingerprints anymore.

 

[1970FuryConv]

Isnt it fun pulling it off of your fingers! Pretty sure I have no fingerprints anymore.

Cool! Now you're completely unidentifiable. Only The Shadow knows who you are. All information related to the BNZ is highly classified.