Bubbles In Repair

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PostPosted: Fri Mar 28, 2008 1:17 am
The work in question is filling license plate holes on a plastic TPO bumper.

In the past I've always used fiberglass resin some matt and Thin Ice to shave holes on plastic bumpers and never had a problem.

Now I decided to step up and use proper products for the job, in this case being Duramix 4240. I roughed up the surface on the front and back. Taped up the front like normal and filled the back with 4240 and some fg cloth for strength. Filled the front with Thin Ice and primered like usual. This repair sat for a few days inside the booth before I shot it with base and clear. Everything looked good at that point. The next day a few bubbles appeared in the repair area. I ground the area out slightly, down to the raw bumper, shot it with some Bulldog filled again with Thin Ice and primered. This time after about 30 minutes two tiny bubbles appeared.

What's happening here guys?
Mike

Don't Listen To Me I Don't Know What I'm Doing

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PostPosted: Fri Mar 28, 2008 7:39 am
If I had to guess it kind of sounds like the Thin Ice went on too quick over the Duramix. That is just a guess. I've done the exact same procedure, no bubbling. Werid...
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PostPosted: Fri Mar 28, 2008 11:00 am
Make sure you allow extra time for the Bulldog to dry.
And...........You haven't wet sanded it have you?
If so then that's probably the problem.
If not, I would have to think it's the Bulldog.
(not to many alternatives here) 8)
JC.

(It's not custom painting-it's custom sanding)



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PostPosted: Fri Mar 28, 2008 11:28 am
I wet sanded but not until after it had epoxy primer on it.

How about a bad mix on the Duramix?

Here's what it looks like now.

Image


I was going to grind out the repair from the back and the front and start over...... but if you guys think I could get away with just Bulldog, Ice and primer it would save me time.

I was reading the directions(when all else fails right) and it says to use cleaner on the repair before and after applying the Duramix.
Mike

Don't Listen To Me I Don't Know What I'm Doing



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PostPosted: Sat Mar 29, 2008 9:26 am
I've done many similar repairs like that without issues. Maybe something
got on there before the basecoat...?
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PostPosted: Tue Apr 01, 2008 4:20 pm
Im looking at this and still cant exactly find out where the problem is. I have seen 4240 bubble from being too hot and from what I see the exotherm temp of thin ice can get up to 205 degrees F...BUT...that doesnt seem to be the issue caus you would notice the bubbles before priming.

Shouldnt be a bad mix as the worst I have seen from a bad mix from the 4240 is taking a longer time to fully cure and usually if you are using the mixing tips and discarding the first 4" of material that comes out then everything should be mixed perfectly.

I would try doing a thin coat of the 3M Automix 5887 over your 4240 that way you can final sand the product or cover that with any filler and shouldnt run into any problems as the 4240 isnt really designed to be top coated.
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PostPosted: Wed Apr 02, 2008 7:34 pm
Here is another bumper that I was filling in a small gap in between the splitter and the bumper using 4240.

See the small bubble in the center of the pic with another just below and to the left.

I taped the front of this and filled the back first. Let that set up for an hour and pulled the tape. It was hard to the touch so I filled the front that the pic shows. It was perfectly smooth with no bubbles. After about two hours three bubbles appeared.

Image


What the hell am I doing wrong?
Mike

Don't Listen To Me I Don't Know What I'm Doing



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PostPosted: Wed Apr 02, 2008 8:11 pm
Strange... I don't use Duramix products much. But something is
getting trapped in there. I'd grind most of it off, poke the bubbles out
and use a heat gun. then reapply. Actually, it may be a good idea
to preheat the plastic before doing any filler work.

Get this plastic welder:

https://www.autobodytoolmart.com/pc-137 ... elder.aspx

I have an older model that works well. And there's enough material
to pay for itself MANY times over. And after the weld, i use 3M automix
for the front. No failures yet.

1999 SL500 Sport front bumber cover ($1600+ new):
Image


Type polyurethane (thermoSET plastic doesn't resolidify):
Image


Not pretty but very strong:
Image


Air filter box for my truck ($200+ new and a thermoplastic that DOES resolidify):
Image


Image


Image


Very self explanatory.
A man can do all things if he but wills them.

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PostPosted: Fri Apr 18, 2008 4:15 pm
Your problems lies with applying a polyester putty over your duramix. Many plastic repair materials have the same recommendations, Polyester fillers such as thin ice will not adhere to your duramix. Reference your TDS (technical data sheets) before using any unfamiliar product, it will save you much aggravation.

I'm sure the job has probably been completed by now but here is the information for future reference, step 12 is where you've probably gone wrong:

http://multimedia.3m.com/mws/mediawebserver?66666UuZjcFSLXTtmxfaLxf_EVuQEcuZgVs6EVs6E666666--
http://www.autobodyreviews.com



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PostPosted: Thu May 01, 2008 12:20 pm
Thanks for the pics Han. I keep wanting to get some type of plastic welder and haven't gotten around to it.

Good link jimmo4life.

On the last pic that I posted of the bubbles in the material that is all Duramix no polyester filler used. I ended up grinding half way through and applying more Duramix and had the same problem. So I drilled a hole in each bubble all the way through the bumper and filled with resin and it was good to go.

I guess Duramix and I just don't get along. lol
Mike

Don't Listen To Me I Don't Know What I'm Doing
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