David
You are correct. Kyoto mentions specifically PFCs and HFCs, but this is
understood to include derivatives, such as the ethers, which also have
very high GWPs. The problem is that the F-C bond is short and strong
(bond dissociation energy 552 kJ/mol @ 25 °C), as opposed to Cl-C (397)
or, weaker still, Br-C (280). It is for this reason that PFCs are
virtually non-toxic, because the bond will not readily break down in the
body, nor in the atmosphere (nor, for that matter, at even 200+°C in the
vapour-phase machine). It is this stability which is so desirable, yet
also so harmful. Unlike chlorocarbons and bromocarbons, there is almost
no tropospheric (or even stratospheric) hydrolytic or photolytic
breakdown of the fluorocarbon molecules, which is why molecules
containing F but no Cl, Br or I are considered non-ozone depleting. The
3M HFE cleaning solvents are also classed with the DuPont HFC ones,
having GWPs of the same order, albeit 2 orders less than PFC/Es. It is
probable that the first amendment to the KP will specifically correct
this semantic anomaly, but this cannot happen until after ratification
by the appropriate number of countries.
Hope this helps.
Brian
David Suihkonen wrote:
> Brian, I should have contacted two gentlemen via land line, I took
> the easy way out on a Friday afternoon, my apologies. To respond to
> your further comments, it is my understanding that the Kyoto Protocol
> lists 6 gases.carbon dioxide, methane, nitrous oxide,
> hydroflourocarbons, perflourocarbons, and sulphur hexaflouride. Both
> Dupont and Ausimont vapor phase fluids are a perflouropolyether. Not a
> perflourocarbon.You may be correct in the assumption that the 3M FC
> product is a perflourocarbon, but because I do not know for sure, I
> will not comment. If requested, I will post my results of
> conversations with 3M when available. I am unfamiliar with the F2
> product you mention. If you would like more clarification these 3
> fluids, I can relay contact information on these fluid
> manufacturers. Best Regards,David Suihkonen
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