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ad pro on plastic

Is there any harm in applying ad pro to all plastics, prior to priming or sealing? Or can it reduce adhesion in some cases? I know it's necessary on TPO plastics, want to know the science behind how it works. In addition, why does epoxy provide a better bond over a urethane primer on plastic? I want to know the science behind it. thanks guys!


Top Banana
I'd like to know if sanding plastics is better then ad pro when time doesn't matter.
I do know i waited too long after applying ad pro the one time i used it & think it glossed the plastic to where paint stuck worse.
One brand's main ingredient is mek. Tells me it melts the plastic somehow opening pores? I'm just guessing but know i never picked the can up again & chose sandpaper instead with zero problems.
If you run a torch over bare plastic it will greatly improve adhesion of products. JimC told me about this. (I had to add that for credibility)
no its not the solvents that bite into the plastic. there is a dissolved resin in the solvents that stick to plastics but also sticks to paint. as for epoxy adhesion, epoxy always has better adhesion than a urethane. simply because its epoxy, its glue lol. i personally only use adpro on unknown plastic that doesnt melt when i rub a rag with acetone on it. in all other cases i use epoxy.
Generally speaking for automotive work, plastics that float on water need adpro, those that sink don't. Testing a sliver of the suspect material in a glass of water will show what's needed. Make sure to knock the air bubbles off the sliver.

"If it's a floater, it needs promoter."

I've been told by someone who ought to know that adhesion can go down if adpro is used where it's not needed.
I was hoping JimC would have backed me up on the flame treatment. But, the company Polyvance (they produce plastic repair materials) encourages torching the plastic to, in their words, "greatly increase adhesion". They also suggest ADPRO but they sell it too.
Great tip Crashtech, I've always done it that way too. If ad pro is used on plastics that don't float, does it reduce adhesion and why?
I was hoping JimC would have backed me up on the flame treatment. But, the company Polyvance (they produce plastic repair materials) encourages torching the plastic to, in their words, "greatly increase adhesion". They also suggest ADPRO but they sell it too.
Evercoat recommends that procedure when using their #411, and it does work. I find it inconvenient most of the time, so we mostly use #411 over primer or epoxy, and that in small amounts, for nicks and pinholes. Other materials, like SEM #39767, stick fine with the use of adpro. It says it doesn't need it, but it definitely works better with.

@danp76 , I'm not an expert on adhesion in any way, I've only been told that adpro can reduce adhesion on some surfaces. I know for a fact that Bulldog can reduce adhesion over painted surfaces in some situations, so we don't use that stuff at all anymore. I'm sure SPI is different and better, but if you can determine for sure that the adpro is not necessary, eliminating the step is in keeping with the KISS principle.
absolutely, the flame treating works great. effects only last about 30-60min or so. you want to flame treat then do repairs right away. i generally flame treat every hard to stick to or chemical resistant plastic when i have to do any bodywork on it. it would be a procedure generally for a repair area and not something you would typically do to a whole part before paint.
dan, use acetone, lacquer thinner or reducer. you are trying to see if the plastic is chemical resistant. if it is i generally use adpro. if it isnt then no adpro or even sanding of the part is needed because our solvent base paints are going to melt right into it. abs for example.
There are a few exceptions that come to mind that are probably obvious to most of us, but we get all experience levels here, so: The cream or yellow colored urethane that was widely used in the 80's is not solvent reversible but does not need adpro. Neither does Endura, SMC, or Metton, a molding compound used in some semi hoods and big vehicle parts.


Top Banana
I'll add the only plastic i tried a ad pro on was my 93 caddy black plastic bumper fillers.
Headlights nothing but sandpaper.

Question- can plastic that floats be sanded instead of ad pro?
An example of plastic that needs adpro would be a new, bare Toyota bumper. It feels greasy when you unwrap it. We wipe them down inside and out with #700 before anything. Wiping the inside helps keep contaminants from migrating due to handling. Then they get scrubbed to death with a gold pad and special prep paste. After that, another wipedown with #700. Just before spraying, a special wipe with de-ionized water and alcohol, wipe in one direction only helps to keep static down. Then adpro, sealer, base coat, clearcoat.

So, I guess you could say that some plastics need every trick in the book, sanding, cleaning, adpro, everything.
use a torch and quickly pass the tip of the flame across the plastic. you are not trying to heat the plastic up. its not about the heat, its about a flame contacting the plastic surface. it relieves surface tension and allows the plastic to accept adhesives,paint, fillers, etc.
oxy would be little overkill and you might get things too hot. just propane or mapp gas is all that is needed. just the flame tip needs to contact the plastic for a split second. the plastic shouldnt even get warm.