OH Index

How does one calculate the 'OH index' of polyols for use in PU
synthesis - or is this a value that is experimentally determined. Is
it the number of moles of OH contained within a Kg of polyol - I am
comfortable using normal stoichiometric calculations but would like to
get to grips with this type of PU industry nomenclature.
Kind regards,
Gillian
Reply to
GillianH
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It's normally quoted as the "OH number". This is expressed as the number of milligrammes of KOH per kg of resin that would contain the equivalent number of OH groups (strange I know). So, if you have a diol of 1000 molecular weight, the OH value would be 56100 (molar weight of KOH expressed in mg) x 2 (functionality) / 1000 (molecular weight of diol) = 112.2. Actually 1000MW diols are usually quoted as OH value 110, or a range from 107 - 113 or something similar.
Kind regards
Colin
Dr Colin D Reed Business Development Manager Rosehill Polymers Ltd
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Reply to
Colin Reed
Colin's reply refers to OH number, not OH index. In the context of viscoelastic foams, which are often made using a stoechiometric excess of OH groups, the excess can be quantified using "OH index" by analogy to yhe more widely used "NCO index". NCO index = 100* (nb of NCO equivalents)/(nb of OH + water equivalents) OH index = 100* (nb of OH + water equivalents)/(nb of NCO equivalents) where nb of equivalents = nb of moles of NCO or OH groups or 2* nb of moles of water in a given amount of (mixed but not reacted) polymer liquids used to make the foam. This should normally be explained in patents which refer to this parameter. "GillianH" a écrit dans le message de news: snipped-for-privacy@g49g2000cwa.googlegroups.com...
Reply to
infinitum
OK, in the context of polyols alone, the term OH index, is indeed as explained by Colin. But "OH number" is also a frequent alternative, I believe. I thought from GillianH's previous post that he was interested in viscoelastic PU foams, where OH index is used with another meaning.
"Oliver 'Ojo' Bedford" a écrit dans le message de news:dok36o$ibq$ snipped-for-privacy@lnx107.hrz.tu-darmstadt.de...
Reply to
infinitum
I think I made it clear that I was defining OH number. From the OP's request I thought that she was interested in OH number and had just used the other term.
Colin
Reply to
Colin Reed

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