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  #31 (permalink)  
Old 06-12-2013, 01:04 PM
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Quote:
Originally Posted by jcclark View Post
Well I'm confused, I thought it was only mechanical when you had to sand it.
1) That's why you sand it, no chemical bond so you need a mechanical which
means scratches for it to hold on to.

2)Chemical means not needing sanding, yes?

3)Anyway-if solvents can go through the epoxy primer then
I can't believe it's waterproof like it's advertised, right?

4)Can it be a sealer and waterproof but solvents can penetrate to the metal?
What I've done is broken down your questions so that I can be sure that I am answering your questions to the best of my ability.

1) Chemical adhesion is a totally different animal than mechanical...mechanical does mean "sticking to sand scratches"...you still have chemical adhesion regardless, if you sand something and open up the pours, you will have more chemical adhesion as well as mechanical.

2) Chemical adhesion does not mean that you don't need to sand a substrate. With respect to Epoxy primer you have chemical adhesion qualities for a period of time without sanding because the pores in the primer stay open for a certain amount of time. After that window, you need to open those pores again by sanding so that you get chemical adhesion as well as mechanical.

3) As I mentioned in my previous post, water molecules are larger than solvent molecules so something can be waterproof and not be solvent proof. Solvents used in paint have harsher more active ingredients in them than water which means they can penetrate or breakdown a cured substrate easier than water, not just because of the size of the water molecule versus the solvent molecule, the sheer chemical make up of a solvent versus water makes solvent penetrate easier.

4) Simple answer to question #4 is yes. Epoxy primer can be a waterproof sealer but solvents can penetrate the sealer and go down to the metal, especially if the Epoxy has been sanded and opened up so the solvents have easy access.

I know it's confusing but...and...I hope this explains things a bit more.

Ray

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  #32 (permalink)  
Old 06-12-2013, 01:42 PM
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I'm surprised at you Jim, I'm sure you know that all epoxy manufacturers recommend sanding and recoat with epoxy before anything else if out of the recoat window. Then you can get a chemical bond.
I think you guys are missing the point. You talk about following the manufacturers recommendations and they have this covered. Nothing sticks to epoxy like more epoxy, so if out of the recoat window you sand and apply more epoxy, then use what ever other coating and it will have chemical bonding. Am I wrong?
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  #33 (permalink)  
Old 06-12-2013, 01:58 PM
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Your not wrong, you will have chemical bonding using epoxy primer or whatever...you will have chemical bonding if you sand or open up epoxy primer and top coat it with base coat, single stage, more epoxy primer...if the epoxy has gone passed the window and you sand it...sanding it opens the window for you...because the the primer is sanded you will have mechanical adhesion...because the primer is sanded and opened up, you will have chemical adhesion.



I'm hoping this helps

ray
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  #34 (permalink)  
Old 06-12-2013, 04:59 PM
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Originally Posted by 69 widetrack View Post
It is confusing, the water molecule is larger than the solvent molecule
No, Ray, I play a scientist for 45 hrs a week and I'm here to tell you a water molecule is most certainly NOT larger than a solvent molecule. I don't even where you would have heard this!

Let's compare water and a solvent:

Water: H20; F.W.=18; molecule diameter=1.93A

That's two Hydrogens and one oxygen


Pick a solvent. For instance, acetone

Acetone: C3H6O; F.W.=58; molecular diameter=3.08A

That's 3 Carbons 6 Hydrogens, and 1 Oxygen.

In fact, almost any molecule you can pick of anything is going to be larger than a water molecule.
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  #35 (permalink)  
Old 06-12-2013, 05:14 PM
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Why in the world is the "scientist" not answering the question then! Explain it to us Lizer, please.


Brian
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  #36 (permalink)  
Old 06-12-2013, 05:17 PM
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MAN !!!!! Now y'all really going to far with this ....
This will really blow people's mind...
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  #37 (permalink)  
Old 06-12-2013, 05:22 PM
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Originally Posted by Lizer View Post
No, Ray, I play a scientist for 45 hrs a week and I'm here to tell you a water molecule is most certainly NOT larger than a solvent molecule. I don't even where you would have heard this!

Let's compare water and a solvent:

Water: H20; F.W.=18; molecule diameter=1.93A

That's two Hydrogens and one oxygen


Pick a solvent. For instance, acetone

Acetone: C3H6O; F.W.=58; molecular diameter=3.08A

That's 3 Carbons 6 Hydrogens, and 1 Oxygen.

In fact, almost any molecule you can pick of anything is going to be larger than a water molecule.
Then I stand corrected and I thank you for pointing that out. I wouldn't argue with a scientist. This however is what I was told (at an ICI seminar if I'm correct) and not having your background, I believed it.

Would it be correct then in saying that a solvent such as a reducer (I realize that water is a solvent as well) would have active ingredients in it that would start to dissolve or break down or should i say open up a substrate faster than water...that's why something can be waterproof (to a point) and not solvent proof?

You being a scientist and acetone being a fairly aggressive solvent...is it the 3 carbon atoms that make acetone that aggressive? Or is it the combination of the carbon and hydrogen together with the 1 oxygen atom that make it a liquid that causes it to be aggressive.

Thanks Again...always like to learn

Ray

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  #38 (permalink)  
Old 06-12-2013, 05:31 PM
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MAN !!!!! Now y'all really going to far with this ....
This will really blow people's mind...
I'm getting my slide ruler out!

Brian
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  #39 (permalink)  
Old 06-12-2013, 05:35 PM
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A slide rule is to big to get through Epoxy Primer Brian...LOL
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  #40 (permalink)  
Old 06-12-2013, 05:35 PM
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I'm getting my slide ruler out!

Brian
I have ALL my safety equipment READY !!!!
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  #41 (permalink)  
Old 06-12-2013, 09:37 PM
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Originally Posted by 69 widetrack View Post
Then I stand corrected and I thank you for pointing that out. I wouldn't argue with a scientist. This however is what I was told (at an ICI seminar if I'm correct) and not having your background, I believed it.

Would it be correct then in saying that a solvent such as a reducer (I realize that water is a solvent as well) would have active ingredients in it that would start to dissolve or break down or should i say open up a substrate faster than water...that's why something can be waterproof (to a point) and not solvent proof?
It hurts my head to even think where to begin...the general principle is correct, but at the same time it's not accurate. It's correct because you make accurate use of the term 'dissolve,' as that's what's happening. Acetone, for example, is the solvent, the solute would be the components of the paint, etc. Thus this is dissolved by the acetone and it all becomes a single solution.

Where it's not accurate is looking at it as if it breaks down something 'faster.' There are 4 chemical conditions that define a solvent's abilities: hydrogen bonding, polarity, dipole moment, and polarizability. Don't worry, I had to consult my chemistry text to make sure I got those right, and is bringing back lovely memories of my undergrad. But I only state that to demonstrate the complexity of everything at play.

To break it down further, solvents are classified into 2 categories, polar and non-polar. There's a textbook phrase in chemistry that goes 'like dissolves like.' Meaning, polar solvents can only dissolve polar compounds, and nonpolar solvents can only dissolve nonpolar compounds. Water is polar, oils and waxes are non-polar, this is why these two will separate. But sugar is polar, and you can dissolve that with water.

But now let's make this even more confusing, water and acetone are both polar. So WTF! you say. Well that's because there are two 'sub-genres,' if you will, of polar solvents--protic (water), which solvate negatively charged ions (anions), and aprotic (acetone), which solvate positively charged ions (cations). Thus the mechanism by which these two solvate are largely divergent. So the chemical makeup of paints or primers would have to be largely cationic. Proteins, which are what I work with, tend to be negatively charged (anionic) and tend to solubilize in water pretty well, though they may not be stable long term.

So what does all that mean in simple terms? Well, there's a giant chemical orgy and in the simplest terms, ions are getting exchanged all over the place, which literally rearranges compounds. But certain things are only capable of dissolving certain things, all due to very specific chemical properties of the solvent--which are the four solvent properties I listed earlier.

Quote:
You being a scientist and acetone being a fairly aggressive solvent...is it the 3 carbon atoms that make acetone that aggressive? Or is it the combination of the carbon and hydrogen together with the 1 oxygen atom that make it a liquid that causes it to be aggressive.
It would be due to the fact that the specific elemental arrangement of these carbons, hydrogen, and oxygen, and their specific ionic properties define the four characteristics I note above. So I had to look it up, but acetone has a pretty large dipole moment, which is important in the chemical reaction that takes place. Let's just leave it at that

I'm a veterinary microbiologist, not a chemist (though chemistry is central to all science), so don't get too eager in your questions because I DON'T know it all!!!
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  #42 (permalink)  
Old 06-12-2013, 10:43 PM
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It's Amazing what you can learn on a forum... But I have to say this is way over my head....
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  #43 (permalink)  
Old 06-12-2013, 11:55 PM
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there are those who do it right and those who stayed at motel 6 once.
this happens anytime 2nd line or relabeled crap is brought up. some guy comes on praising eastwoods new paint or summits new paint or how they painted their show car with omni . the smart thing for a professional to do is ignore and not post. but like barry told me once , if we dont speak up some poor guy with 2 years into his hotrod tries something and then discovers it all has to come off . when on a tight budget this is a disaster . but the google expert is nowhere to be found when it happens.
when i am building an engine i go to a professional for advice. i do not want to hear a bunch of bs from someone who changed an intake . take a look in the engine builders forum . those poor guys have been run ragged by google experts reading hotrod magazine.
maybe a better sub forum would be one for professionals to answer question but only after proof they do it for a living or own a shop. but that wont happen .

spi thug and proud of it ................... use to be a ppg thug but nobody whined about it.
The problem with compairing SPI to say DuPont, are many, starting with the fact that cars painted with spi are most likely babied, garaged and well cared for.
I don't know how it hold up in the "REAL WORLD" a fair weather daily driver that sits outside 95% of the time. rock chips and other crap a car that is used more than it sits ,will get.
THIS is important as the lawn chair car guys are loosing footing to those that build and DRIVE the crap out of their junk.
has anyone got a vehicle that was painted 8 years ago that had to deal with bird crap,rock chips, highway sandblasting(from sand in the wind), rain(and not wiped off within hours), and the sun most of that time..
and some might think these are not important, they also own trailor queens that are also garage queens, that then cross an auction block as new build.. the rest of us that drive the wheels off our junk ,it is very ,very important!!!.. KOK is a great paint for the show car and looks killer, but as far as holding up to mother nature it's a big fat fail.
but it wasn't made for that, it was the show car paint.
I know how ppg/DuPont/nason,basf,etc will hold up .
and this means more to me than if I have to wetsand out a little orange peel.

and with paint jobs coming in at 5-10g's or more it better dam well stand up to the things mother nature and use bring to the table, if that means I'm a motel6 guy so be it.. the motel 6 guy, SHINE is a person that likes only having to do something ONCE. and it lasting . is that a BAD thing? is questioning or asking questions a bad thing? or is it. I said so, don't question me

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  #44 (permalink)  
Old 06-13-2013, 04:33 AM
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This is my first experience with any kind of forum, and God I never knew what I was missing. I've turned into a teenage girl, first thing in the morning I turn on my computer just to watch this forum and all the excitement. I've been in the paint business for 23 years I never knew paint could be so exciting.LOL Mr. gearhead I must say I like your style and you bring up a lot of valid points.
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  #45 (permalink)  
Old 06-13-2013, 04:54 AM
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Originally Posted by Lizer View Post
It hurts my head to even think where to begin...the general principle is correct, but at the same time it's not accurate. It's correct because you make accurate use of the term 'dissolve,' as that's what's happening. Acetone, for example, is the solvent, the solute would be the components of the paint, etc. Thus this is dissolved by the acetone and it all becomes a single solution.

Where it's not accurate is looking at it as if it breaks down something 'faster.' There are 4 chemical conditions that define a solvent's abilities: hydrogen bonding, polarity, dipole moment, and polarizability. Don't worry, I had to consult my chemistry text to make sure I got those right, and is bringing back lovely memories of my undergrad. But I only state that to demonstrate the complexity of everything at play.

To break it down further, solvents are classified into 2 categories, polar and non-polar. There's a textbook phrase in chemistry that goes 'like dissolves like.' Meaning, polar solvents can only dissolve polar compounds, and nonpolar solvents can only dissolve nonpolar compounds. Water is polar, oils and waxes are non-polar, this is why these two will separate. But sugar is polar, and you can dissolve that with water.

But now let's make this even more confusing, water and acetone are both polar. So WTF! you say. Well that's because there are two 'sub-genres,' if you will, of polar solvents--protic (water), which solvate negatively charged ions (anions), and aprotic (acetone), which solvate positively charged ions (cations). Thus the mechanism by which these two solvate are largely divergent. So the chemical makeup of paints or primers would have to be largely cationic. Proteins, which are what I work with, tend to be negatively charged (anionic) and tend to solubilize in water pretty well, though they may not be stable long term.

So what does all that mean in simple terms? Well, there's a giant chemical orgy and in the simplest terms, ions are getting exchanged all over the place, which literally rearranges compounds. But certain things are only capable of dissolving certain things, all due to very specific chemical properties of the solvent--which are the four solvent properties I listed earlier.



It would be due to the fact that the specific elemental arrangement of these carbons, hydrogen, and oxygen, and their specific ionic properties define the four characteristics I note above. So I had to look it up, but acetone has a pretty large dipole moment, which is important in the chemical reaction that takes place. Let's just leave it at that

I'm a veterinary microbiologist, not a chemist (though chemistry is central to all science), so don't get too eager in your questions because I DON'T know it all!!!
Although I didn't fully grasp everything that you posted, I did understand a fair amount and what I understood was that because water (being a solvent) has different properties, the chain reaction of water on primer is different than say the chain reaction of reducer on primer, making primer more water proof than reducer.

I will stay with my original statement though that sanding a primer aids in mechanical and chemical adhesion of primer to top coat.

I know this is going to sound anal...and I know it is....but, I dug up my old notes from the 80's...and in 1986 this was passed out by a CIL trainer in Edmonton, not ICI, which documented that "because the water molecule is larger than the molecules found in CIL's 2K primer, the water molecule can not penetrate today's high build catalyzed primers". Now I wish that I would have read that statement over before I posted...I would have questioned the fact that water can't penetrate high build primers because as we now know, they can.

So, again I thank you for clarifying the water molecule thing, the last thing I want to do is pass on information that isn't correct.

Ray
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