Coatings toxic breakdown products

[elwarpo]

I was on another gun forum and posted up how using the wrong coating on bullets can produce toxic vapors, and someone suggested I post up here.

First: I am a coatings chemist with 30 years experience inventing paints and coatings. I have dozens of published articles, many patents and travel around training people on coatings technology.

Second: I want to make people aware of the dangers, flame away if you like, but before the dangers were exposed, people thought smoking was healthy also.

Third: It is nearly impossible to tell if a coating will give off toxic combustion products or not. Normal decomposition for organic matter used in coatings is anywhere from 250F to 900F. The temperature the coating is likely to see during firing is above that, and coatings companies do not want to pay for expensive testing of their coatings for conditions they will normally not see. The hot gas from combustion of reloading powder and friction in the barrel will exceed normal temperatures that coatings are subject to.

So what is toxic? Most coatings (especially powder coatings) are pre-reacted from a resin and a crosslinker. The resin is normally epoxy, polyester or acrylic based. Decomposition products from these are normally carbon monoxide and carbon dioxide, but can also contain aromatic functionality. This can lead to benzene in the case of incomplete combustion.

The crosslinker may be the issue. They can be isocyanates for acrylics and polyesters, melamine formaldehydes for acrylics and polyesters, and amines, amides or phenolics for epoxies.

Isocyanates can produce hydrogen cyanide during combustion. It lists this on the SDS.

Phenolics (also known as phenol formaldehydes) are used to crosslink epoxies, they are used in can coatings for food and in powder coatings. decomposition products include "The volatile products included light hydrocarbons, formaldehyde, phenols, aldehydes, ketones, ethers, oxygen-containing heterocycles, fused ring compounds and benzene and its homologues." a lot of which are hazardous.

Melamine formaldehydes (very common crosslinker in coatings that are cured by baking), can give of formaldehyde upon decomposition.
Here is some info on it " exposure to formaldehyde by inhalation is mainly from three types of sources: thermal or chemical decomposition of formaldehyde-based resins, formaldehyde emission from aqueous solutions (for example, embalming fluids), and the production of formaldehyde resulting from the combustion of a variety of organic compounds (for example, exhaust gases). Formaldehyde can be toxic, allergenic, and carcinogenic."

Amines and amides used to cure epoxies give off simple and complex amines during combustion, a lot of which are carcinogenic and are hazardous.

Please post up with specific questions on coatings in general, I will not however say which brand is better than another brand.

[pmer]

What is produced during the cure in the oven? Is it mostly carbon monoxide and carbon dioxide and gases of incomplete combustion?

Oh and welcome to the board.

[clearcut]

So in lay mans terms ??? I PC out doors and shoot out doors should I worry?

CC

[dragon813gt]

So in lay mans terms ??? I PC out doors and shoot out doors should I worry?

CC

He said w/out actual testing there is no way to know. You'd have to test the powders at the temperatures generated during firing to see what the byproducts are. This won't be cheap. I'm wondering if Federal did this w/ their coated bullet line. Due diligence is in order when you're a large company like ATK.

[clearcut]

so one must ask if the micro second the PC'd boolit is heated in the bbl. will it cause the PC to be changed to the point of releasing the offending gasses.
CC

[elwarpo]

So in lay mans terms ??? I PC out doors and shoot out doors should I worry?

CC

Ok, in laymans terms.

In powder coatings, they react 2 components, the resin and crosslinker (think 2 tubes in an epoxy). While there is a reaction, a lot of what you see in powder coatings is the powder melting and flowing. In order for the powder to flow at 300-400 degrees, it is designed to be a low melt point polymer. That is the reason it should not be used. It is not designed for high temperatures.

Typical powdercoatings are designed for a service life below 250F. If you need to have higher temperatures, silicone resins are used (think high heat exhaust paint or barbeque paint). the higher in temperature the higher the cost of the resins. Another issue is the pigments, bright colors (red, blue, green, yellow) are not heat stable. Black, white ochre and rust are heat stable. So any paint with bright clean colors are also not designed for high temperatures. All of this points to you are using the wrong paint on your bullets.

[elwarpo]

He said w/out actual testing there is no way to know. You'd have to test the powders at the temperatures generated during firing to see what the byproducts are. This won't be cheap. I'm wondering if Federal did this w/ their coated bullet line. Due diligence is in order when you're a large company like ATK.

The odds are they are using a coating designed for high temperatures. Silicone or other technologies can make a paint that resists high heat, think muffler/exhaust/ fireplace coatings. standard powder coatings are not designed for high heat/high friction applications.

[elwarpo]

I sent an email to Federal to see if they have tested their ammo for combustion by products.

[elwarpo]

so one must ask if the micro second the PC'd boolit is heated in the bbl. will it cause the PC to be changed to the point of releasing the offending gasses.
CC

I suspect there is, how much I do not know. Moving down the barrel you are definitely vaporizing the coating. Most powdercoatings will reflow with temperature. Simple test - put some powdercoated bullets in the oven at 500F, and while they are still hot, see if the coating is soft. Think of it this way, pure lead melts at 621F, powdercoatings will be destroyed at that temperature. if 621 melt point lead melts in a barrel, powdercoatings definitely will.

[elwarpo]

From this link, most polymers will flash ignite (combust) at temperatures from 400 to 700 F. This is above the decomposition temperature, here the fragments from the broken polymer will vaporize and ignite like gasoline if a spark is present.
http://pslc.ws/fire/howwhy/thermalp.htm

[castalott]

First, Welcome and Thank You for caring about our health.

I'm not sure I know enough to even ask intelligent questions but....


Where does the "HiTek" catalyst paint fit into this?

In general, darker colors tend to be safer?

These toxic combustion products are only given off in 'High heat' settings. How large a volume are we talking about? After the bullet leaves the bore, would the temperature drop enough that the outgassing would stop immediately or is this just the start of a process that 'tapers' down to a halt.

Since I 'recycle' my HiTek bullets, I then have a problem when I melt the recovered ones in the pot? ( Includes PC)

There is a bullet lube many like that is 45% alox, 45% floor wax, and 10 % mineral spirits. (BLL) Do you think a coating of this on the bullets after PC or HiTek would help with the outgassing?


Thanks, Dale

[NoAngel]

I coat outdoors. I shoot outdoors. At my age and current health...PC has been to good a find to let go.
Thanks for the insight. Politely hoping you're wrong.

[elwarpo]

What is produced during the cure in the oven? Is it mostly carbon monoxide and carbon dioxide and gases of incomplete combustion?

Oh and welcome to the board.

Thanks, just trying to make sure people are safe out there.

As for the curing byproducts, if it is melamine formaldehyde crosslinked ( a lot are) you will give off some formaldehyde. but mostly CO and CO2. However in most houses, there is not adequate ventilation, so any fumes will remain in the house.

here is a SDS for an epoxy based powdercoating
http://axalta.ahsserver.com/sds/SDS_...AR_FBE_ENG.pdf

and a polyester one (they do not say what the crosslinker is)
http://axalta.ahsserver.com/sds/SDS_...EEN_II_ENG.pdf

TGIC (transglycidal isocyanurate) is a common polyester crosslinker and is a mutagen, meaning it can mutate (cause birth defects in the mother, and the defects can even be passed on to the baby through the father's sperm). Do you really want to play with that in your house?

[pmer]

My guess is that the projectile or the PC isn't getting hot enough to release toxins. I suppose if you're smelting coated boolits that might be another story. That is regular epoxy powder. Many of us have examined recovered boolits and see no evidence that the surface of the boolit has melted.

[shoot-n-lead]

My guess is that the projectile or the PC isn't getting hot enough to release toxins. I suppose if you're smelting coated boolits that might be another story. That is regular epoxy powder. Many of us have examined recovered boolits and see no evidence that the surface of the boolit has melted.

That was my thought exactly...and I suspect that the gun powder is emitting as much offensive gas as the pc'd bullet ever would.

[runfiverun]

maybe not in the gun.
but during the 'wet' stages of curing this could occur much easier.
the 400-f curing [crosslinking] point would be the most dangerous point for outgassing the by products.

[JimB..]

Interesting. I defer to your expertise, but have a couple questions.

If you consider that common lubricants for cast bullets do not appear to flash during firing, would that help narrow down the max temp that the coating is exposed to?

Also, I think that there have been exceedingly few reports of pigment left in barrels or suppressors, if the coating was being vaporized, wouldn't you expect it to be deposited on the cooler surfaces?

Finally, if one had access to a university lab with a mass spectrometer, wouldn't identifying the products at various temperatures be straightforward? I expect that finding the actual temp of the bullet would be more difficult.

[castalott]

If you consider that common lubricants for cast bullets do not appear to flash during firing, would that help narrow down the max temp that the coating is exposed to?

Quote...


Hi JimB... Just a thought here.... maybe the heat is enough to flash the lubricants but the trip down the bore doesn't provide enough time or enough expansion space for them to do so.

Dale

[dverna]

maybe not in the gun.
but during the 'wet' stages of curing this could occur much easier.
the 400-f curing [crosslinking] point would be the most dangerous point for outgassing the by products.

This makes the most sense. I certainly would not cure in a house or unventilated space

Don Verna

[pmer]

Thanks, just trying to make sure people are safe out there.

As for the curing byproducts, if it is melamine formaldehyde crosslinked ( a lot are) you will give off some formaldehyde. but mostly CO and CO2. However in most houses, there is not adequate ventilation, so any fumes will remain in the house.

here is a SDS for an epoxy based powdercoating
http://axalta.ahsserver.com/sds/SDS_...AR_FBE_ENG.pdf

and a polyester one (they do not say what the crosslinker is)
http://axalta.ahsserver.com/sds/SDS_...EEN_II_ENG.pdf

TGIC (transglycidal isocyanurate) is a common polyester crosslinker and is a mutagen, meaning it can mutate (cause birth defects in the mother, and the defects can even be passed on to the baby through the father's sperm). Do you really want to play with that in your house?

Thanks for the information, I hope no one is curing powder in their house. I think most of us casters understand ventilation. I have sprayed boolits and used the shake-n-bake method and also do some other coating projects in my welding shop. It seems easier and faster than painting when all you need to do is sand blast, clean, coat, bake and use the part as soon as it cools down. A cheap spray gun in a booth can waste a lot powder compared to the shake-n-bake method a lot of people are using for boolits and you can lay them flat on a non stick surface to cure. I don't know if you are familiar with swirling small parts in a plastic bowl to get powders to adhere to the parts.

I'm not sure how to say this but that hasn't stopped me before.. I don't see a list of precautionary statements when I open a shipping box with a pound or two of powder inside. My last pound of John Deere green had a packing slip and a bag of powder and nothing to indicate any health warnings. Maybe that is just my supplier but it might help to spread the news in regard to safety having some info with the package.