| Group | Wave number (cm−1) | Vibration type | Assigned to |
| -C-H | 2985 - 2810 | Stretching | PP |
| -CH2 | 2950 - 2850 | Stretching | HDPE |
| -CH2 | 1475 - 1440 | Bending | PP |
| -CH3 | 1380 - 1370 | Bending | PP |
| -CH2 | 1470 - 1460 | Bending | HDPE |
| -CH2 | 730 - 700 | Rocking | HDPE |