I think you're overreacting on his comments. It was an epic struggle, but I couldn't resist. Sorry.
Dewey
-----Original Message-----
From: Leadfree [mailto:[log in to unmask]] On Behalf Of Hogg, Blair K.
Sent: Friday, June 29, 2007 8:38 AM
To: [log in to unmask]
Subject: Re: [LF] Norwegian legislation
Brian,
Am I interpreting your posting as saying it is possible that manufacturers would add excess epichlorohydrin to ensure that all of the TBBPA is reacted?
Blair
-----Original Message-----
From: Leadfree [mailto:[log in to unmask]] On Behalf Of Brian Ellis
Sent: Friday, June 29, 2007 4:51 AM
To: [log in to unmask]
Subject: Re: [LF] Norwegian legislation
That is all true, Gordon. However, there is something else that is not considered. BPA and TBBPA are monomers, but neither contain the epoxygroup used crosslinking. This is usually supplied by epichlorohydrin, another liquid in the prepolymer reaction. If the excess happens to be this substance, what will the consequences be?
Epichlorohydrin is a very probable human carcinogen, teratogeand reduces sperm count and motility and is somewhat volatile. Does this say anything, when its vapours can slowly leach out from the resin mass into the air of your living room?
Brian
Davy, Gordon wrote:
> A forum subscriber emailed me directly to inquire about additive use of TBBPA. I started to reply directly to him, and then I realized that there are probably others who would like more of an explanation, so I'm replying to the forum instead.
>
> The Norwegians say about cheap electronics from Asia, "There are reasons to presume that TBBPA used as an additive exists in many imported products such as inexpensive consumer electronics and electrical toys produced in Asia, however it is difficult to survey the extent." That says to me that they are guessing about whether TBBPA is used additively. They don't know, but think that it might be, and they want to play it safe.
>
> If you are not a polymer chemist, you may not recognize the distinction between reactive and additive, but that is what must be understood. TBBPA is a monomer, as is bisphenol A, one of the substances used to make many epoxies, and also regulated by the Norwegians. Both are liquids. It is the content of the monomer that the Norwegians regulate, because that is what they perceive as being able to migrate within the environment and enter the biosphere as a pollutant.
>
> When monomers react, they become a part of a polymer and are no longer distinguishable as the substances they once were. In particular, the polymer now contains bromine (still covalently bonded), but it would take a very sophisticated analysis to show that the bromine atoms were once a part of TBBPA. Apart from the unreacted monomer, the TBBPA no longer exists. It is comparable to the case you may recall from high school chemistry, when oxygen and hydrogen mixed in a 1:2 ratio react - those substances disappear and you get water. If the two reacting species are not mixed in a perfect 1:2 ratio, whichever one is present in excess will remain unreacted and will be present with the water.
>
> The issue then becomes, how much unreacted TBBPA, or bisphenol A remains when polymerization is complete? That depends on how well the amounts of the reacting constituents were controlled, but they are usually controlled well enough so that the monomer content is well below one percent. That is what the Norwegians recognize and discuss. They discuss this more in the section on bisphenol A, which comes before their discussion of TBBPA. (Incidentally, TBBPA stands for tetrabromobisphenol A, so you can see the similarity. In reactive use, the TBBPA is simply substituted for some of the bisphenol A in measuring out the reacting constituents.) Here's an excerpt:
>
> A Norwegian survey shows very large variation in different products on
> the markets varying from less than 10 mg/kg free available residuals
> to about 2500 mg/kg... _Potential exposure to the consumers may occur
> if free monomers are made available_ or if the polymer is damaged or
> degraded, for example in epoxy resin-based paint, wood fillers and
> glue. [Emphasis added.]
>
> In discussing TBBPA they say "The level of free residual is quite low, so that the direct exposure of consumers is probably insignificant." Note the phrase "free available residuals." They say that the amount of unreacted bisphenol A varies from 10 ppm to 2œ percent. I'd expect something like that range for unreacted TBBPA as well. Typical values, as they say, will be well below one percent, simply because the presence of too much unreacted monomer degrades the properties of the polymer and is wasteful.
>
> The amount of unreacted monomer is determined by extracting it from the polymer with a solvent or with steam. That ability to be extracted it is what they are concerned about - it may be extracted (e.g., by ground water in a land fill) after the product has been discarded.
>
> Gordon Davy
>
>
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