As above.
Or will it depend on the resin and hardener utilized?
Any reading recommendations on cured epoxy? (I am more interested in the covalent bond and chemical structure of cured epoxy)
Thank you very much!
Dear Emmanuel:
Sorry, but you are not right:
What is the curing mechanism of anhydrides used as epoxy curing agents?
Dow Answer Center:::
http://dowac.custhelp.com/app/answers/detail/a_id/3868/~/dow-epoxy---anhydride-curing-mehanisms
Here is the final product of a 3-stage curing of Epoxy by Anhydride
The epoxide groups react with nascent or existing hydroxyl groups, catalyzed by the acid, producing an ether linkage + OH
Best Regards, Leonid
dear Leonid,
let me precise my answer.
on the same site, you can find that there are several possible anhydride/epoxy ration.
- If there is a stoechiometric ratio, the isopropanol will react with anhydrides.
- Otherwise, some isopropanol will open other epoxide rings during post cure.
you can have a look at a FTIR spectra of a cured epoxy anhydride system in F Delor Jestin et al, Polymer Degradation and Stability, Volume 91, Issue 6, June 2006, Pages 1247-1255 (we did a lot in the lab for a PhD still running). You will see that there is actually very low concentration in OH after curing.
so the precise answer would be: much less OH in epoxy anydride than in epoxy diamines. Do you agree?
regards
Dear Emmanuel:
you "switched" the question by adding the 3rd component: isopropanol. In this case isopropanol will react with anhydride groups - thus reducing the amount of anhydride hardener (because of esterification). Yes, and in this VERY case - the concentration of OH-groups in the total reaction product will be lower than if the diamine is used. Moreover - if you'll take a very high concenration of isopropanol - you'll "kill all the anhydride groups -- BUT the OH-groups of the Epoxy Resin - will still remain.
Regards,
Leonid
ok, we agree ... let me also remind you that for industrial purpose, anhydride are used very often in slight excess (increasing Tg for example).
regards
OK, we came to agreement. The only thing to add is that the OH-groups of 2-propanol
look almost the same as OH-groups formed after the epoxy cycle opens. THUS the concentration of OH-groups which came from epoxy will certainly depend on the concentration of your solvent. For clear-cut experiment you should not use 2-propanol.
Best Regards, Leonid