These articles might be helpful.
1. https://www.mdpi.com/2073-4360/12/12/3054/htm
2. Article Recent advances in epoxy resin, natural fiber-reinforced epo...
3. Article Mechanical and wear properties of epoxy matrix composite rei...
Dear Ravi SHANKAR Rai, the best hardners for epoxy resins are thiols (mercaptans) and aliphatic amines. Acids and their anhydrides are also used. Literature on these systems are straight via simple search. My Regards
Thank you Abdelkader BOUAZIZ sir for kind suggestions. please help me with the mixing ration and prerequisites during mixing and making FRP samples.
No thanks Sir. Attached is an interesting overview on epoxy curing chemistry and systems. My Regards
Dear Ravi SHANKAR the choose of epoxy-hardener depends allways on application, because the hardener is mostly a big part of the emerging material.
Dieter Kunz sir, the purpose is to enhance the mechanical properties especially impact strength of the CFRP and light weight as needed for automobiles and aircraft.
The stoichiometry is quite simple. For every hydrogen you need one epoxy group, that means for a SH or NRH you need one epoxy group, for a NH2 you need two epoxy groups. Let's take for example IPDA as amine hardener. It has a molekular weight of 170 and contains two amino groups, that means 4 active hydrogen. Therefore the hydrogen equivalent weight is 170/4 = 42.5. The epoxy equivalent weight (EEQ) of a typical technical Bisphenol-A-diglycidylether is e.g. 190. The stoichiometric mixture ist therefore IPDA : epoxy resin 42.5 : 190 per weight for this example. But the stoichiometry must not be as accurate as in polyurethane systems. Epoxy resins are tolerant to mistakes.
For anhydride hardened epoxy resins you need a 1:1 stoichiometry for cyclic anhydride : epoxy group. But theses systems are slower and need higher temperatures fo curing.
Burkhard Koehler Sir, thank you so much for such a detailed explanation.
Dear Ravi, this is a very general question since it depends on the kind of epoxy resin and the kind of product you require. Most hardners used for epoxy are amines but it can be a primary (quick cure) or secondery or tritary amine (slow cure). Also the ratios depend on the resin. if it is a pure epoxy it can move between 10-30/100 if the resin is filled it can be 1:1.
thank you so much for sharing your knowledge and giving me the clarity on my work. Alisa Buchman thanks a lot.
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