Paint - isocyanate alternatives

Yes Gonzo you put the finger on:
Acrylic can be used without hardener (and it works well with good duration) or if you want more resistance to chemicals you can add a hardener but it's an isocyanate. The hardener gives a harder coat and tougher to chemicals. Also a brighter surface. Perfect for a car with the gas spilling, oils, waxes, silicones and polishers, not so useful for the topsides of a boat.
True acrylic (nothing in common with the so called acrylic house paints) can be found waterborne and it works pretty well. Very good price also (10 to 11 USD a litre here, the mexican and excellent brand NERVION, specialist of industrial paints), usable with brush, roll and others systems.

 

Urethanes can be sprayed without hardener too. For example, the paint in cans for touchups is without it.

 

Yes , but the urethane (carbamat) paints are not in the big league of tough paints at my knowledge like epoxies, polyurethanes (different stuff from urethanes), with the acrylics just behind.
A good indicator is to look in the catalog of a brand of good industrial paints for hard use (planes, boats, trains, tooling, etc). You'll see immediately which are the winners...
In fact is more interesting to get rid of the solvents that represent something like 60% of the volume of the paint. There is not innocuous solvent except water. Most are flamable, a lot are very toxic, a few are carcinogenic. Being vapors, solvents are easily inhaled, or a very expensive equipment is needed.
It's why I switched to waterborne acrylics. It's easy to be protected of a paint aerosol with a simple equipment. It's one of the reasons I also prefer epoxy resins (which have very little vapors) to polyester resins, full of solvents like styrene; easy to be protected from epoxy, almost impossible from polyester.
And I won't talk of the fire hazard...

 

No discussion of using powder coating? I find it extremely durable and there are methods that require < 100C to melt the powder.

 

Powder coating can be an excellent method in its domain but impractical for big objects like a boat. It asks also for an oven, equipment very expensive in the big sizes with the common difficulties to get an even temperature everywhere.

It seems to me that it's rather difficult to cook an entire boat in polyester which has already been finished inside. I imagine the melted grease of the winches running everywhere, the lexan windows gently falling down and the plywood making bubbles in its varnish...in industrial fabrication of GRP boats it does not compete with a gelcoat, it do not seem convenient on metal boats, which need a complex system of sandblasting, primary, filling and several coats of paint and wood...I do not imagine a classic or composite wooden boat cooked in a oven, it will fall apart. Most resins or glues used in shipyards get soft over 60-80° Celsius.

Other problem; how to repair or remake a such paint?

It's more an large industrial scale method for industries like fabrication of fridges, for objects that won't be repainted, than for yacht shipyards, generally small scale enterprises (and under capitalized).

 

Thanks.

 

You're welcome Jonr, powder coating is excellent in "small" metal pieces and can be done at small scale.

My opinion (shared by many others) is that isocyanates are indeed a health problem, but solvents are finally far more dangerous and insidious.

With appropriate (and rather inexpensive) equipment you can be protected from aerosols. It's "easy" to not be in contact with the liquid form, simple disposable clothes protect from the the aerosol particles, and efficient filters for breathing are simple and cheap. "Catching" the particles can be achieved by a lot of means, almost nothing is released in the outside atmosphere. So pollution is limited to an acceptable level.

Solvents evaporate, are inhaled, and permeate through the skin as liquids or gas. Personal protection is costly to achieve. Carbon cartridges are inefficient as they saturate very fast, positive pressure air breathing systems and totally sealed clothes are mandatory. I wouldn't accept to "absorb" even "acceptable" levels of any solvent during years.
And remains the problem of the solvents released into the atmosphere...

 

Isocyanates tend to be far more a problem in the workplace than products like styrene, neither is good for you though. We sell products with both ingredients and the potential health issues from even short term exposure to Isocyantes can be very serious and require an immediate emergency trip to a hospital. Isocyanates can be inhaled and/or absorbed through the skin in the same manner as solvents and they require a spray booth with much better ventilation than styrene requires.

People sensitized to Isocyanates can have a serious reaction by just passing through a building where its being used, even if its a great distance away.

 

Yes you are right, isocyanates are very dangerous and powerful sensitizers (a part the toxicity) and the allergic reaction can go until death. It is unhappily the same problem with some epoxy hardeners and more common products like eggs, peanuts, oysters, bees and wasps venom, horsefly saliva and a lot of medications, vaccines etc...
Some isocyanates like the toluene one contains a double toxic.

But it's found mainly in the aerosols particles (you can trap in a filter and inactive it with a carbon filter) and not in great quantities likes solvents, that represent about 60% of the weight of the paint.
As solvents do not cause spectacular reactions like allergic shock, and apparently have not immediate serious adverse reactions in a short lapse if time, they seem less toxic so more tolerable. It's that I call insidious, like abestos, tobacco smoke and general pollution. That takes years, but a lot of solvents can kill you, slowly.

And solvents are pollutants, dissolved by the ventilation, not destroyed or trapped nor inactivated and will go everywhere. Imagine the millions of tons of solvents released in the atmosphere...

Besides, as I do love good food and great wines, I hate to lose the sense of smell for days because of styrene. Without sense of smell, no good sense of taste. Life becomes very sad.

That explains why I do prefer in my very small scale a waterborne acrylic without hardener...preferably rolled when possible.

 

All the epoxy paints I've used had very strong solvents. They were very unpleasant to use.

 

Hi Guys, doing an epoxy laminate and apparently epoxy gelcoats UV yellow? Can a polyurea coat be used in mould instead?

Tks