Putting polyurethane in a crib is not something I would recommend. It's just not worth the risk. Chemical exposure is accumulative. Those early days are so precious and sensitive.
Looking at the ingredients I would expect fast drying oil based poly to take at least a month to fully coalesce together and begin to cure tightly. Poly generally gains hardness over the first year. In 3 months it typically tests a little harder than after the first 30 days. That means bonds are tightening and solvent may be coming out. Some big box store poly’s took the gaggingly nasty naphtha out of the fast dry poly and now use a couple varieties of mineral spirits. Because of the tightness of the double urethane bond I'd expect it to take many months for all of the mineral spirits to come off; maybe a year or more inside a house under normal temperatures and airflow. I’ve walked into restaurants many months after they used poly and it still stunk up my dinner. That’s because it was still off gassing. Some studies show voc’s off gassing up to two years later.
My biggest problem with poly is the isocyanates.. Oceans of toxic isocyanates are made every year, poisoning the earth for profit and performance.
MDI and TDI and the most common diisocyanates used in polyurethane production. They react with a polyol kind of the way epoxy does, making it more stable. When polyols are reacted with diisocyanates it creates the double urethane bonds. Judging from the color and lack of UV resistance of the some big box poly I would guess they use an MDI, maybe the Toluene Diisocyante. It's too cheap to be Aliphatic Diiosocyanate or a Triisocyante. Some may argue that it is all reacted with the polyol but I have not found this to be true and my chemical engineer has actually been able to create reactions to existing isocyanate in raw polyurethane resin by initiating an entirely new process in a reactor. But it doesn’t really matter to me because I don't want any of this stuff left over, unreacted, near my kids. Not even trace amounts.
Some big box polyurethane’s lays down very thin and have a nice flow. I would guess they are using additives to help with this. Other than a few acrylic based flow and leveling agents most of the others I'm familiar with have pretty strong, toxic solvents as the vehicle. This almost never gets mentioned on the label because if it's not a carcinogen and if it’s not over a certain level it doesn't need to be listed legally. Additives are generally designed to be used under 2% by weight so most are never listed.
Add these risks to the accumulative exposure a child is going to encounter over the next ten years and bammo! It’s just not worth it.
The best finish for a crib is the Special Linseed Oil Wood Finish
with a coat of the Looking Glass Beeswax Polish
on top. These are pure, 100% natural, plant based finishes with zero driers or additives. No isocyanates, ever. No mineral spirits. Just pure plant based, super filtered flax oil, beeswax and a dash of citrus to make it easy to apply.
Response to a Conventional Wood Finisher about Isocyanates in Polyurethane on Cribs.
“I want to say thanks for your response. You’ve gotten me to revisit the whole polyurethane topic which is worthwhile and I appreciate your insight. I welcome any corrections to my opinions here.
I wouldn’t go so far as to say we are keeping the world safe with Polyurethane but there’s a place for it. Not in wood finishing and cribs since I find it to be lacking and toxic. I don’t want poly, it’s additives, solvents, minerals spirits near an infants lungs.
Agreed on the point of quality. Premium poly is better and less likely to have residual isocyanate. I don’t have big box poly on my list of premium poly. There may be more reliable processes than spectroscopy to insure no free isocyanates remain in a coating. It’s a whole extra process. It’s expensive to do. It just doesn’t happen much. Those who do it usually talk about it because it makes a better product and raises costs.
I believe over indexing is the standard in the polyurethane industry; adding a little more isocyanate than is necessary to insure maximum creation of the urethane bond.
I talked it over with a manufacturer, Chemical Engineer I know in the industry; it seems that even if ATR Spectroscopy is used throughout the process it’s still an art and takes a real master. Apparently residual isocyanate is plausible even when measuring n-c-o levels and rate of isocyanate consumption; that even without error residual isocyanate is not unlikely because of over indexing and the fact that spectroscopy might not pick it all up.
Another thing someone brought up today is that with a polyurethane dispersion, like the one mentioned for the crib, blockers are typically employed in these situations, this helps block the reaction. It has been questioned if even NMR would pick up residual isocyanate effectively in this scenario. A pretty big question when you consider the sales volume of poly dispersions.
It doesn’t take much of this odorless toxin to do damage. Nobody really knows what trace amounts are actually doing and more needs to be revealed. I wouldn’t bet my kids health on the idea that batches go through without trace yet unhealthy amounts of isocyanate. Especially, when they are churned out in high production batches for big box and trade sales. Bayer is the first and now biggest poly maker but I’m more impressed with the lengths Wasser goes through to address isocyanates. Check out this link http://www.polymer-services.com/Isocyan-2000.pdf
Bottom line, unless the manufacturer is specifically quantifying no free isocyanates I don’t buy it.”