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Old 09-09-2019, 06:46 PM
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Urethane vs Arcylic enamel with hardner

I've been reading about paints quite a bit and everything I have read has said that urethane paints are by far superior to arcylic enamels. I have read that the urethanes are much harder than the arcylic enamels but I have not been able to find anything comparing the acrylic enamel when it has a hardner in it. I assume the urethane is still going to be better than the arcylic even when it has the hardner but is it enough to justify trying to risk spraying the urethane because of the iso stuff it contains. The stuff in the urethane truly frightens me which is probably good thing but I know it can be done safely with a fresh air system but I also fear the safety of others because I would be spraying out side. I also understand there may be some iso in the a in the hardner for the arcylic but you could get away if just a good respirator and the suit right? Is the urethane really that much better than acrylic when it contains the hardner?

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Old 09-09-2019, 08:41 PM
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The best plan is to follow the manufacturer's data sheets. Period.
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Old 09-09-2019, 09:41 PM
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I do think the urethane is better but I painted a '47 Ford convertible with Sherwin Williams acrylic enamel with Polysol (their hardener)in about 1978. I sold the car to a friend in 1992 and he just had it re-painted 4 years ago. 36 years for a paint job isn't bad and the car still looked pretty good.

BTW, with the hardener, I color sanded and buffed the car just like you would a urethane.

I do believe though the catalyst does contain Isocyanates so be careful with it.

John
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Old 09-10-2019, 06:01 AM
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Wow I honestly thought I wasn't gonna see any replies for a coue of days, thanks
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Old 09-10-2019, 06:48 AM
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I was taught that all topcoat catalysts are based on the same raw ingredient. Like crude oil, an endless number of recipies make different useful things from it. But "how much" is the only real variable. The enamel hardener contains the same hazard but to a lesser degree. As far as durability, nobody can quantify the "how much better is urethane" better than you can, knowing what you want to paint, how much you can spend, and quality expectations. An enamel is oxidizing anytime it is exposed to air, urethane is not. Pick your poison amount.
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Old 09-10-2019, 07:12 AM
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The disposable respirators out these days are quite good. Make sure ahead of time it is adjusted to fit properly. I saw one guy with a beard slather vasoline on it (the beard) where it was letting air through. They seem to keep well for quick little jobs also if you seal them up air tight as soon as you remove it. If you can smell paint, it's leaking air or used up. Much easier than holding your breath.
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Old 09-10-2019, 07:14 AM
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Matt brings up another good point. The car I painted was a non metallic light color. Had it been metallic it most likely would have been a different story as far as longevity goes.

John
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Old 09-10-2019, 08:23 AM
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Both will have hardener in them. Acrylic enamel usually mixes at 8:1 while Urethane 4:1, in my experience. For all I know, that's the only difference > the mix instructions .

For primers and paints, data sheets are of utmost importance. Once you get into rust removers and conversion coatings, a lot of fly by night companies promise a bit too much simplicity on the label, so it's best to do some research on specific processes and products.
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Old 09-10-2019, 08:51 AM
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Anything that has a hardener, catalyst, or activator is going to have isocyanates in it. There are some ISO free primers out there but they are labeled specifically.

Most urethane's have a better gloss and hold up much better then acrylic enamel by a large margin.

On the masks get a Niosh 95 or better. 3m. Gerson, SAS all make them. Some of the ones in Lowe's /Home Depot look identical but are only good for pesticides and below. As per 3m, the N95 masks are good for roughly 8-10 paint hours. Pull it out assemble it, paint, pull the pre filters off, store them to the side, and back in it's zip lock bag it goes. If you leave it on the bench overnight assembled the carbon filters are pretty much done.

https://www.amazon.com/dp/B000MP6566..._t2_B0038TD8BI

https://www.amazon.com/DuPont-Indivi...20&s=hi&sr=1-3 Put your rubber gloves on and masking tape the cuffs snug if they don't have elastic.

Last edited by Hipster_G; 09-10-2019 at 09:12 AM.
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Old 09-10-2019, 09:03 AM
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Quote:
Originally Posted by dwighty390 View Post
Both will have hardener in them. Acrylic enamel usually mixes at 8:1 while Urethane 4:1, in my experience. For all I know, that's the only difference > the mix instructions .

For primers and paints, data sheets are of utmost importance. Once you get into rust removers and conversion coatings, a lot of fly by night companies promise a bit too much simplicity on the label, so it's best to do some research on specific processes and products.
I'm sorry but there is a lot of incorrect information here.

Acrylics and urethanes are chemically different. Some acrylics do not need hardeners though they greatly improve the quality of the acrilycs. AAMOF for years hardener was not available for them. Laquers dry by evaporation. Enamels dry chemically through combining with oxygen , and urethanes dry by chemical reaction to the catalyst. That is why Matt said the enamels were continually oxidizing.

The mixing ratios are based solely on the manufacturer's formula. Many high end urethanes mix 1:1 paint and catalyst. SPI clear included. Dupont combined their catalyst with their reducer.

Taking this subject just a little farther, One of the common problems with the cheaper lines of paint is they require less reduction. This requires buying more paint to get the same amount of sprayable material. Also, they will have less pigment, requiring more coats.

If you buy a paint that reduces 2:1 you will get 1 1/2 gallons of paint. If you buy a paint that reduces 1:1 you will get 2 gallons. Now if the cheap paint requires 4-5 coats instead of 3, how much money do you think you have saved?

John

Last edited by John long; 09-10-2019 at 09:14 AM.
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Old 09-10-2019, 09:04 AM
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Quote:
Originally Posted by Hipster_G View Post
Anything that has a hardener, catalyst, or activator is going to have isocyanates in it. There are some ISO free primers out there but they are labeled specifically.

Most urethane's have a better gloss and hold up much better then acrylic enamel by a large margin.

On the masks get a Niosh 95 or better. 3m. Gerson, SAS all make them. Some of the ones in Lowe's /Home Depot look identical but are only good for pesticides. As per 3m, these masks are good for roughly 8-10 paint hours. Pull it out assemble it, paint, pull the pre filters off and store them to the side, and back in it's zip lock bag it goes. If you leave it on the bench overnight assembled the carbon filters are pretty much done.

To take this further, get the SILICONE 3M masks (blue), not the cheaper grey ones.

I think the correct cartridge for painting is 7046/6001 and it is super important to keep fresh air coming into your paint area, even with the best mask available.
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Old 09-10-2019, 09:10 AM
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Quote:
Originally Posted by John long View Post
I'm sorry but there is a lot of incorrect information here.

Acrylics and urethanes are chemically different. Some acrylics do not need hardeners. AAMOF for years hardener was not available for them.

The mixing ratios are based solely on the manufacturer's formula. Many high end urethanes mix 1:1 paint and catalyst. SPI clear included. Dupont combined their catalyst with their reducer.

Taking this subject just a little farther, One of the common problems with the cheaper lines of paint is they require less reduction. This requires buying more paint to get the same amount of sprayable material. Also, they will have less pigment, requiring more coats.

If you buy a paint that reduces 2:1 you will get 1 1/2 gallons of paint. If you buy a paint that reduces 1:1 you will get 2 gallons. Now if the cheap paint requires 4-5 coats instead of 3, how much money do you think you have saved?

John
I have not yet seen an acrylic enamel that was not intended to be used with a hardener. Comparing an acrylic line to the urethane line within a brand, I have noticed that the urethane is always mixed with more hardener/catalyst and that the hardener/catalyst is identical between the 2 lines. I'm not sure where the incorrect information is. Perhaps you are saying that this hasn't been my experience?
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Old 09-10-2019, 09:14 AM
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Quote:
Originally Posted by dwighty390 View Post
I have not yet seen an acrylic enamel that was not intended to be used with a hardener. Comparing an acrylic line to the urethane line within a brand, I have noticed that the urethane is always mixed with more hardener/catalyst and that the hardener/catalyst is identical between the 2 lines. I'm not sure where the incorrect information is. Perhaps you are saying that this hasn't been my experience?
It doesn't look like this holds true for ful-cryl/ful-thane, actually. I recall that differently in using them in the past, but they are both 8:1

So I'll say that some I have used mixed at different ratios with the same activator
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Old 09-10-2019, 09:28 AM
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Acrylics don't need a hardener to dry though most manufacturers do offer one. It does improve gloss and durability some what. Without hardener some gas or brake fluid spilled is a disaster. Dupont, Nason, Sherwin-Williams Dimension, etc all still offer acrylic enamel.

Most mixing systems I've worked with will share a set of toners. Toners take up roughly 1/3 of the mix formula. It is in the binder which is 2/3 of that gallon of paint that makes the difference in chemical composition. They take different hardeners. With urethane you better get the hardener right or it will still be sticky 2 years from now.

Typically with synthetic/alkyd enamels they call it catalyst, with acrylic enamel they call it hardener, and with urethanes commonly referred to as activator these days.

Last edited by Hipster_G; 09-10-2019 at 09:36 AM.
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Old 09-10-2019, 09:31 AM
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I used Ful-cryl to do the inside of a pickup box one time, and kept what was left to touch up. The touch ups did not dry where I used it without adding the hardener, so some apparently do need it to dry in this lifetime.
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