Hallo each, Can any one provide any information, or point me to a source of information, about the yellowing, in storage, of PTMG ether/MDI thermoplastic polyurethanes, for example, Pellethane?
Specifically, I am interested in the chemical species formed, or the elimination products. Is there the formation of any oilgomers - dimers, trimers, etc?
Thanks for your help Regards, Bill
Hi Bill
The reason the PUs are yellowing is due to the action of UV light on the MDI component of the polyurethane. Its kinda difficult to explain without the chemical symbols but it does not affect the properties of your material. No bonds are broken within the polymer
Hi, Gerry, Thanks for your reply.
I'm familiar with the yellowing and discolouration of pvc by thermal degradation, the formation of unsaturated carbon - carbon bonds in the polymer backbone, and by the elimination of HCl
I can imagine that in the MDI part of polyurethane, because of electron-withdrawing properties of the oxygen atom, or even the nitrogen, that some carbon - hydrogen bonds might be a bit unstable.
I have read, in your note, and in some books, that there is no deterioration of mechanical properties of PU when it is exposed to uv and goes yellow. Although I cannot disclose the application for the PU that I am using, I am concerned that a discolouration must be due to some chemical change in the polymer, and that any elimination products may be toxic.
Please can you help me a bit further, or point me to some authoritative book and/or published papers on the subject?
Much obliged for your help, Regards, Bill
Gerry wrote:
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