[Machuu]

Hello everyone, I'm writting thesis about FT-IR analysis of polyolefins like LDPE, LLDPE, HDPE, iPP and block copolymers of PP-PE. On PP and PP block copolymers spectrum appears unknown band for me (2723 cm^-1), and I can't find any informations about it. Could anyone help me and tell where can I find answers? Picture shows iPP spectrum

I will be gratefull for your help.

[Corribus]

It shows up in my ATR spectra of PP as well and is not officially assigned in any of my literature resources. However it shows up at slightly lower than double the energy of the δCH₃ symmetric bend mode (1376 cm^-1 on my spectrum). So it may be an overtone of that transition.