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 Post subject: Gluing light plastic
PostPosted: Sun Aug 08, 2021 2:29 pm 
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TBI Slant 6

Joined: Sat Oct 12, 2019 11:42 pm
Posts: 156
Car Model: 1962 Dodge Dart
Hi everyone,

I'm repairing the rear taillight on my 62 dart. The plastic has broken cleanly and fits back together nice and tight. I would normally use something like Krazy glue for this, but wanted to see if anyone had any recommendations due to the difficulty finding these.

Paul


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 Post subject: Re: Gluing light plastic
PostPosted: Sun Aug 08, 2021 5:32 pm 
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Supercharged
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Joined: Wed Oct 12, 2005 9:00 pm
Posts: 2887
Location: kankakee IL
Car Model: 80 volare, 78 fury 2 dr, 85 D150
how weather resistant is Krazy glue? that would be the biggest issue I can think of..... certainly not a place for the old standby, JB Weld, though.....


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 Post subject: Re: Gluing light plastic
PostPosted: Sun Aug 08, 2021 7:32 pm 
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Supercharged

Joined: Wed Sep 17, 2008 6:48 pm
Posts: 3825
Location: Indianapolis
Car Model:
With a tight piece to piece fit I would use super glue. That product works really well in situations like that. If it was a loose fit I would use a solvent based glue that would fill the gaps.
In either case be really careful to not over apply the glue, any residue glue that is forced out when the two pieces join will likely not have the gloss and luster of the OE lense.
And that is where super glue will have an edge. A really light coat on each edge, join the pieces together, hold for a moment and you are done. Again I would be very light on the glue application

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 Post subject: Re: Gluing light plastic
PostPosted: Sun Aug 08, 2021 8:50 pm 
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Joined: Thu Oct 31, 2002 5:39 pm
Posts: 24463
Location: North America
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Do not use cyanoacrylate (super glue, krazy glue, etc). Not only is it almost certainly not very good for gluing this kind of plastic, but it will also want to turn the plastic near the glue to an ugly white chalky substance. There are fully-transparent cements intended for plastic repair—use one of those.

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 Post subject: Re: Gluing light plastic
PostPosted: Sun Aug 08, 2021 10:51 pm 
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Supercharged

Joined: Thu May 12, 2005 11:50 pm
Posts: 6291
Location: So California
Car Model: 64 Plymouth Valiant
If the plastic is acetone safe, you can clean up the white chalky residue.

Although it's rather impossible to clean up if it's not a smooth surface.

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64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

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 Post subject: Re: Gluing light plastic
PostPosted: Mon Aug 09, 2021 7:28 am 
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TBI Slant 6

Joined: Sat Oct 12, 2019 11:42 pm
Posts: 156
Car Model: 1962 Dodge Dart
It has also been recommended to me to use clear Gorilla Glue. I'm not too worried about gloss and luster as these lights already have cracks and are missing some of the...fins?... This is a "better than a big open hole" repair. Dan, I will do some research into the fully transparent cements. My only concern is trying to find one that will not yellow over time, but that may not be avoidable.

Thanks for the input everyone.

Paul


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 Post subject: Re: Gluing light plastic
PostPosted: Tue Aug 10, 2021 6:06 am 
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Board Sponsor & Moderator
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Joined: Mon Oct 21, 2002 11:08 am
Posts: 16797
Location: Blacksburg, VA
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Does anyone know what material these lenses are made of? They feel like they might be polystyrene. If so, plastic model glue would work really well. I tend to agree with Dan that super/krazy glues might not be the best. Hmmmmm

Lou

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 Post subject: Re: Gluing light plastic
PostPosted: Tue Aug 10, 2021 10:10 am 
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Joined: Thu Oct 31, 2002 5:39 pm
Posts: 24463
Location: North America
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Probably acrylic.

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 Post subject: Re: Gluing light plastic
PostPosted: Tue Aug 10, 2021 12:32 pm 
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Supercharged

Joined: Wed Sep 17, 2008 6:48 pm
Posts: 3825
Location: Indianapolis
Car Model:
Quote:
fits back together nice and tight.
That one statement by possibly the only person on this forum that has actually seen the part in question is why I would lean towards super glue.

Super glue bonds extremely well when it is applied in a very thin coating. I would be looking at a drop of super glue on some hard disposable surface and then using either a pointed toothpick or a very-very fine tipped pencil brush to dip into that drop and apply a thin sparse coat of super glue to each of the two halves. You will basically get one chance to piece the two parts together, hold for a moment or two and you are done. After the repair is complete, the glued joint will just be maintaining its own position, there should not be any added loading applied as it is a tail light lense, perhaps mounted in a housing.

My concern with a solvent glue is; enough glue for the solvent to react with and soften the plastic is necessary for that process to work. With a tight joint, glue beyond the space available in the joint when to two parts are set together will be forced out. That could make the repair noticeable. Unless the repaired part is self stabilizing, one should also have a clamp-support-fixture to keep the parts in alignment until the solvent glue sets.

and
Quote:
will not yellow over time
keep the glue inside the joint and you should just see the edge view of the crack, you should not see the glue.

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 Post subject: Re: Gluing light plastic
PostPosted: Tue Aug 10, 2021 12:49 pm 
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TBI Slant 6

Joined: Sat Oct 12, 2019 11:42 pm
Posts: 156
Car Model: 1962 Dodge Dart
Thanks Dadtruck, I've worked on a number of models and done some ceramic repair over the years and superglue has been good for them. I'll take a look at a superglue and the clear gorilla glue to see which might be better.


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 Post subject: Re: Gluing light plastic
PostPosted: Tue Aug 10, 2021 8:04 pm 
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Joined: Thu Oct 31, 2002 5:39 pm
Posts: 24463
Location: North America
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If it were my taillight, I'd use Bondic, which is water-clear, UV-cure, not-solvent-based.

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Too many people who were born on third base actually believe they've hit a triple.

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 Post subject: Re: Gluing light plastic
PostPosted: Wed Nov 03, 2021 4:23 pm 
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TBI Slant 6

Joined: Sat Jul 08, 2017 2:06 pm
Posts: 173
Location: NC
Car Model: 78’ dodge D100 slant six
Well being the person I am I’m going with something different from everyone. I would try and separate the pieces. Then use a clear fill epoxy to glue them back and then a whole layer all over it. Just my two cents.


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 Post subject: Re: Gluing light plastic
PostPosted: Sun Oct 27, 2024 7:36 am 
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TBI Slant 6

Joined: Thu Nov 09, 2023 5:12 am
Posts: 146
Location: Hudson Valley, NY
Car Model: 1964 Dart 270 4-Door
Add my vote for Bondic.

I bought some months ago on Dan's advice, finally got around to taking off my taillight.
It was "mushed in" in a "nose out of joint" position, and I was dreading the possibility that it would disintegrate in my hand, but it just pushed right back into its anatomic position, with no fuss, and no "extra" chips - Just "Bip!"

I used the Bondic, and it worked just like it's supposed to. I used it before over the past few months on other small projects and every time, I've been happy.

It is slightly visible when the light is on, because I used it to fill in some of the "refraction bumps," but only if you're right up next to it, staring at it - you'd never see it driving in traffic.

One thing that isn't explicitly mentioned in the Bondic instructions is that it is UV-cured.
They advise you to use their tiny UV LED bit, which works well, but if you're working outdoors in bright sun, you won't need it, and, in fact, the glue can set before you intend it to if you're working in the sun.

Thanks, Dan!

- Eric


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