Hi again science forums!

Me again, back with a bit more material related question.

As someone with near zero background in chemistry, I want to know if polyurethane ( sometimes referred to as PU) foam is safe?

My preliminary readings and research shows that a residue called " isocyanates" left over by the processing of polyurethane foam, among others, could be quite problematic. There are articles on the internet suggests that it is best not to use mattresses with polyurethane foam as the stuffing.

Again, I want to know what people who specializes in this or have received higher education in chemistry think of this?

In what capacity are you asking is it safe? 

I wouldn't recommend eating  it. 

On 29.12.2017 at 1:48 PM, MC1992 said:

Hi again science forums!

Me again, back with a bit more material related question.

As someone with near zero background in chemistry, I want to know if polyurethane ( sometimes referred to as PU) foam is safe?

My preliminary readings and research shows that a residue called " isocyanates" left over by the processing of polyurethane foam, among others, could be quite problematic. There are articles on the internet suggests that it is best not to use mattresses with polyurethane foam as the stuffing.

Again, I want to know what people who specializes in this or have received higher education in chemistry think of this?

 

I worked on PU foam R&D for 8 years so I know a bit about it.  Isocyanate is highly reactive and is all consumed in the manufacturing process.  Such foams are widely used in cot mattresses and institutional bedding.  The combination of mattress cover and condition is highly significent in safety terms. I wouldn't buy a secondhand one in any case.  Modern formulations are safe although there have been questions related to cot death and I would not advise using a secondhand one for babies, especially very young ones.  There was also govt. advice to lie babies on their backs.  Again, I wouldn't buy a secondhand one.

 

There were also concerns about the extreme flammability of early formulations and much development focussed on dealing with this problem and you would be advised to check flammability ratings on any products you have.   Latex foams do not suffer from the same potential disadvantages but again should be checked via manufacturers advice.

Isocyanates react with water (which is always present in the air). Even if the manufacturing process didn't get rid of them, the air woud.

Some foams are potentially rather flammable, but there's no  great risk associated with them.

Haven't worked with Isocyanates for over 25 yrs.
And it was MDI, not TDI which is more dangerous.
All I remember from the MSDS is that it has a built in warning mechanism. In the case of low exposures, it is a sensitizer; so if you start breaking out in reddish splotches, get rid of any  PU foam mattresses and avoid them in the future. If you don't break out in splotches, there is no appreciable exposure.

Isocyanates are associated with asthma in sensitive persons. IIRC this:

12 hours ago, Tobyjug said:

Isocyanate is highly reactive and is all consumed in the manufacturing process. 

was generally assumed to be true, but  recently more sensitive methods were used and isocyanates were  detected in a wide range of cured products. However, and quite commonly in these studies, it is not quite clear whether the detectable amounts pose health hazards. As MigL mentioned, once symptoms show up (which can be skin sensitization or asthma-like symptoms) it is better to replace them. Likewise, hypersensitive individuals may be better off not having those products around.

7 hours ago, MigL said:

Haven't worked with Isocyanates for over 25 yrs.
And it was MDI, not TDI which is more dangerous.
All I remember from the MSDS is that it has a built in warning mechanism. In the case of low exposures, it is a sensitizer; so if you start breaking out in reddish splotches, get rid of any  PU foam mattresses and avoid them in the future. If you don't break out in splotches, there is no appreciable exposure.

Describing occupational asthma (which is a permanent condition) as a "warning mechanism" is, at best a poor joke.

4 hours ago, CharonY said:

 

... recently more sensitive methods were used and isocyanates were  detected in a wide range of cured products. 

The measurement of "free isocyanate" is about as close to religion as analytical chemistry gets.

Almost any technique that could measure it could also generate it, so it's a matter of faith whether the free isocyanate was present or not.

Polyurethane safety is related

I had heard that the EU were banning isocyanate use for anyone but trained contractors and paint applicators. i.e. - you won't be able to but 2 pk PU paints from shops anymore, but you could hire an approved contractor to come round to supply and apply it for you. I am not sure how far we have progressed along this route yet.

 

 

5 hours ago, John Cuthber said:

The measurement of "free isocyanate" is about as close to religion as analytical chemistry gets.

Almost any technique that could measure it could also generate it, so it's a matter of faith whether the free isocyanate was present or not.

So if I understand it correctly the issue is that known extraction methods would also  release bound isocyanates? 

Essentially the answer to that is "maybe".

Isocyanates themselves are very reactive and are often derivatised before analysis by reaction with, for example, dibutlylamine.

The substituted dibutyl urea is then measured by GC/MS.

 

However, it's perfectly possible for the dibutylamine to react with a polyurethane and to give exactly the same product. (you don't see ammonolysis as often as hydrolysis- but it still happens)

Similarly, anything that involves heating the polyurethane  might cause it to decompose forming isocyanates.

My view is that, regardless of the apparent measurements (and there are studies that support both sides), isocyanates are unstable in the presence of water and  there's always water around.

 

My use of Methyl Di-Isocyanate was limited to liquids John.
There was no aerosols or blowing involved, and MDI is not particularly volatile.
Routes of entry were by skin exposure, not vapor inhalation.

I assure you no joking was meant.
( although my jokes are usually poor )

Methyl diisocyanate doesn't make sense. Do you mean methylene diphenyl diisocyanate?

The route of exposure isn't as important as you might expect.
It's possible to get asthma by skin contact with these things.

Yeah, you're right.
We just shortened MDI to Methylene di-isocyanate, since TDI is Toluene di-isocyanate.
( cut me some slack, the last chemistry class I took was last year of high school, 40 yrs ago )

And, yes, we did use organic cartridge respirators for MDI, and supplied air in the rare use of TDI.

I know of one person who became slightly sensitized and wasn't allowed to work with isocyanates anymore. I still work with him at my current place of employment where we make Phosphine ( much less dangerous  ). His only symptoms were the allergic type, skin reaction.
I did not know you could get respiratory problems from skin contact.

 

The problem is when people also shorten hexamethylene diisocyanate (AKA HDI) to Methylene di-isocyanate

and then get one or other mixed up with hydrogenated MDI (AKA HMDI) officially known as bis isocyanatocyclohexylmethane

 

They seem to have chosen a bunch of compounds that are bound to get muddled.

I've sprayed polyurea coatings upon several projects, and the key to success is using the right equipment and technique. High-pressure, heated plural-component sprayers are essential for proper mixing and application. Surface preparation is crucial; ensure the area is clean and dry to achieve optimal adhesion. 

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