i have done experiment on curing of epoxy L12 Hardener k6..Made a Neat composite..Ratio taken 10:1...But while checking tensile strength of neat composite i obtained very less values (23-30) as compared with company standard values of 60-70..What will be problem during the curing process..Any suggestions
Dear Linto,
I´ve seen, you already got several notes. In general it is absolutely necessary to very strictly adhere to the stoichiometric ratio given by the manufacturer. Any remaining uncrosslinked contents of resin or hardener can act as softener in the cured epoxy and strongly decrease the mechanical properties. Are there further any details mentioned by the manufacturer regarding the cure cycle? Often an additional short-term post-curing at elevated temperatures is recommended for a full hardening and therefore significantly enhances the properties. Moreover, porosities due to e.g. incorporated air in the blending process of the components can lead cracks and thus to an ealy failure.
Best regards
Alexandra
You can increase the catalyzer amount, futhermore is very important that you make cured kinetic by DSC or TGA.
Dear Linto,
Refer to the data sheet for the ratio, curing details, post curing instructions etc.
was the tensile test sample cut properly, were the resin and hardener mixed properly, So much deterioration is not possible
You have not mentioned the manufacturer of the resin system.
Some discussion concerning the benefits of a detailed kinetic analysis can be found here:
https://www.researchgate.net/post/What_are_the_practical_uses_of_doing_a_detailed_analysis_of_the_kinetics_of_curing_process
Additionally you can check for homogenous mixing.
best regards
Matthias
Added to the above answers, please monitor shelf life and pot life. Are the resin and the hardener free from moisture ?
Dear Linto,
I´ve seen, you already got several notes. In general it is absolutely necessary to very strictly adhere to the stoichiometric ratio given by the manufacturer. Any remaining uncrosslinked contents of resin or hardener can act as softener in the cured epoxy and strongly decrease the mechanical properties. Are there further any details mentioned by the manufacturer regarding the cure cycle? Often an additional short-term post-curing at elevated temperatures is recommended for a full hardening and therefore significantly enhances the properties. Moreover, porosities due to e.g. incorporated air in the blending process of the components can lead cracks and thus to an ealy failure.
Best regards
Alexandra
In addition to the above notes, it is always recommended to perform some characterisations with new resin/hardener systems. For instance, a DSC measurement can reveal any traces of uncured resin (look for typical resin exho and thermo peaks) or incomplete reaction. Basically no exothermic reaction within the curing temperature range of a supposedly cured sample should be identified. To define your curing profile, you can either rely on the data sheet, or do your own measurements through rheometry (temp. ramp to find the curing point, and isothermal measurements of the storage and damping moduli for curing time).
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