I guess you are asking about which DGEBA band/specie is related to its toughness at FTIR spectra. I recommend to use instead some mechanical testing, given they are highly reliable, meanwhile FTIR is semi-quantitative.

Resin toughness can be increased by the addition of

- mineral fillers

- elastomers

- thermoplastics

All three exhibit somewhat different morphologies. First you should make optical or SEM micrographs on fractured surfaces, you may also try to enhance the contrast by cehmical or plasma etching. Then you may try to identify the additive by comparing the IR spectra of pure epoxy (provided that you know the crosslinker) with the toughened compound.

Dear Gyorgy Banhegyi,

Many thanks for your useful answer.

The main problem is no access to chemichal formula and resin data sheet because of reverse engineering.

Dear Victor H Ponce,

Thanks for suggestion, but I already performed relevant mechanical tests.

I woulsuggest then to try to use Raman microscopy or IR microscopy, if available. That may help in idetifying the phases.

Dear Prof Gyorgy,

I already performed FTIR test. For further information and note your practical suggestions, I attached the FTIR result of un aged sample.

Please have a look at the following publications:

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3270863/

I did not have time for a detailed analysis, but is seems that your system is similar to that shown in Fig. 3. of the above publication. The 465 1/cm band may be due to silica filler.

There is a good chance that the impact modifier is CTBN, see the spectra in:

http://hal.archives-ouvertes.fr/docs/00/25/33/61/PDF/ajp-jp4199404C8119.pdf

especially the 2177 CN stretching is very specific.

You may also consult the following publications: https://www.researchgate.net/publication/230342246_Hydroxyterminated_polybutadiene_toughened_epoxy_resin_Chemical_modification_microstructure_and_impact_strength

Article Hydroxy‐terminated polybutadiene toughened epoxy resin: Chem...

 Dear Prof Gyorgy,

So many thanks for useful links, you are definitely right the toughned compound is CTBN.

Dear Prof Gyorgy,

After aging samples and performing FTIR test, the peak at 3426 cm-1,1714 cm-1, 1558 CM-1 respectively decreased comparing un-aged FTIR result. They could be an indicator for degrading CTBN.

That would need a more detailed analysis. The nitrile peak did not decrease at all.

Dear Prof Gyorgy Banhengyi,

You are totally right but please concern this fact that i am doing research on incipient thermal damage which composite is not truly in aging stage which DMA results proved this stage. However, tensile tests showed relative increase in stiffness and impact resistance test remarkable reduction in composite toughness.

Is there any reliable evidence in FTIR result to exhibit toughness deterioration?

Regards,

Amin Khajeh