I tried making composite out of Araldite CY-230 epoxy and HY-951 hardener. But it is remaining in gel form and not solidifying. What may be the possible reason?
One simple explanation, probably, I can add to previous answers, namely, unsufficient quantity of hardener. Really, I have observed during long time the gel form of epoxy resin in bottle which was polluted by a little quantity of hardener.
The solubility of Hardener is usually rather slow. Actually in epoxy-hardener system a much better solvent for hardener is the product of the initial stages of reaction (induction period). Basing on these facts I propose to introduce the hardener in several portions. This approach in my opinion will result in fully cured solidified material.
Regards, Leonid
Sir you mean to say that hardener should be mixed in small quantity instead of mixing it in once?
I am agree with Leonid V. Vladimirov in opinion that step adding of hardener allow us to improve of solidification process. At whole, the careful mixing of enough viscous epoxy resin with relatively small portion of hardener is a very important. The reasonable heating of epoxy resin aimed on reducing of viscosity before mixing is seemed useful too.
Dear Dr. Jyotiraman De:
In my note (see above) I shared with you my observations on how to achieve the most effective mixing of epoxy resin with hardener. And "YES" - the addition of hardener in several portions (not at once) - seems to be the best way. By special experiments it was shown that the solubility of hardener in the products of its reaction with epoxide is substantially higher than solubility of hardener directly in epoxy resin.
Dr. Serge V. Shil'ko added some more details and I agree with all of them.
Good Luck to you with your experiments, Leonid
Dear Dr. Leonid V Vladimirov and Dr. Serge V. Shil’ko,
Thank you for your suggestions. I would try as you suggested and let you all know the results.
Regards,
Jyotiraman De
Dear Dr. Serge V. Shil’ko,
i have one query on your suggestion. Should the epoxy resin be allowed to cool till room temperature or the hardener be added to epoxy resin when the epoxy resin is hot?
Regards,
Jyotiraman De
I do not know the exact composition of your epoxy resin, neither of hardener. But anyhow - because the reaction is exothermic - you should NOT over-heat the composition trying to reach full solubility of hardener fast. Nor should you try to dissolve hardener at low (say, room temperature). By "try-and-errors" method you will find the optimal temperature which will lead you to desired properties of the resulting product. [[ from my own experience of curing Aromatic Epoxy Resins by Aromatic diamines -- the "optimal temperature " at the start of reaction was about 40-50C ]]].
Regards, Leonid
Dear Jyotiraman De, my coleagues just have expressed their opinion about your question. Really, you may heat the epoxy resin carefully before mixing and 40-50 C is admissible temperature for it. Of course, the optimal value of temperature depends on quantity of epoxy resin. When you take large quantity of resin (more than 20 g), the temperature should be reducing to prevent "explosive" exothermic polymerization with porous structure formation.
Regards, Serge
Dear Dr. Leonid V Vladimirov and Dr. Serge V. Shil’ko,
Thank you for your valuable guidance. I made 2 samples, mixing hardener with resin at room temperature and another after heating the resin at 45 C for half an hour. Rough sample was made for experimentation to visualize the solidification process neglecting the bubble formation. And happily the composite cured in less than 20 hours.
The 2 major factors were:
i) Mixing the resin-hardener composition till the change in viscosity or gel formation is observed.
ii) Heating the resin at 45 C made the liquid viscous and it resulted to more faster reaction. This was concluded by the rapid gel formation observation compared to the unheated resin-mixture composition.
Regards,
Jyotiraman De
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