Hii..

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

Please help..!

I didn't find the right solution from the Internet.

References:-
http://www.chemicalforums.com/index.php?topic=93853.0
case study examples

Thanks!