Table 1: Vibrational Combination Bands of Polylactic Acid (PLA).
| Calculated position (cm-1) | Observed position (cm-1) | Assignment |
|---|---|---|
| 4725 | 4770 | νasCH3 + νC = O (1780) |
| 4725 | 4725 | νasCH3 + νC = O (1740) |
| 4635 | νsCH3 + νC = O | |
| 4420 | 4438 | νasCH3 + δasCH3 |
| 4351 | 4372 | νasCH3 + δasCH3 |
| 4330 | 4307 | νsCH3 + δasCH3 |
| 4330 | νasCH3 + δ(CH) wagging | |
| 4260 | 4255 | νsCH3 + δsCH3 |
| 4240 | νsCH3 + δ(CH) wagging | |
| 4233 | 4217 | νasCH3 + (νCOC + δCH) |
| 4180 | 4175 | νasCH3 + (νCOC + ρ asCH3) |
| νCH3 + δCH | ||
| 4143 | 4135 | νsCH3 + (νCOC + δCH) |
| 4098 | 4086 | νasCH3 + ρasCH3 |
| 4090 | νsCH3 + (νCOC + ρasCH3) | |
| 4065 | 4051 | νasCH2 + νCOC |