Table 5.
Thermal properties obtained during the first DSC scan of annealed (A) and composted (C) films of neat and plasticized PLA, PHB, and PLA/PHB blends at different test times. (n.d.: not detected; for these samples, Tg could not be detected in the DSC thermograms).
| Time (d) |
Tg,PLA (°C) |
Tm,PLA (°C) |
ΔHtot,PLA * (J/g) |
Tm,PHB (°C) |
ΔHtot,PHB * (J/g) |
||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| a | c | a | c | a | c | a | c | a | c | ||
| PLA | 0 | 61.8 | 152.1 | 0.8 | |||||||
| 7 | 51.5 | 54.5 | 156.1 | 154.6 | 32.4 | 37.5 | |||||
| 14 | 44.5 | 51.8 | 153.7 | 153.5 | 39.7 | 39.8 | |||||
| 28 | n.d. | n.d. | 135.4 | 144.2 | 42.4 | 66.2 | |||||
| PLA/TB | 0 | 45.4 | 150.6 | 0.5 | |||||||
| 7 | n.d. | 44.6 | 151.9 | 153.5 | 32.5 | 35.8 | |||||
| 14 | 45.8 | 56.4 | 149.3 | 148.3 | 40.8 | 55.4 | |||||
| 28 | n.d. | / | 134.9 | / | 57.6 | / | |||||
| PHB | 0 | 172.9 | 85.3 | ||||||||
| 7 | 171.7 | 169.9 | 81.8 | 82.4 | |||||||
| 14 | 170.7 | 170.8 | 100.8 | 100.9 | |||||||
| 28 | 169.3 | 170.2 | 92.9 | 87.0 | |||||||
| PHB/TB | 0 | 168.1 | 63.9 | ||||||||
| 7 | 162.4 | 171.4 | 66.2 | 78.1 | |||||||
| 14 | 161.5 | / | 72.8 | / | |||||||
| 28 | 161.1 | / | 79.7 | / | |||||||
| PLA/PHB(7:3) | 0 | 59.3 | 153.6 | 4.3 | 172.6 | 17.9 | |||||
| 7 | 61.3 | 60.8 | 155.8 | 156.4 | 30.1 | 24.5 | 172.5 | 170.8 | 20.5 | 16.7 | |
| 14 | 48.2 | 55.3 | 155.4 | 154.2 | 35.9 | 36.7 | 170.1 | 167.9 | 20.8 | 17.0 | |
| 28 | 39.5 | 53.6 | 137.1 | 141.8 | 45.6 | 35.5 | 155.4 | 157.8 | 25.6 | 18.9 | |
| PLA/PHB(7:3)/TB | 0 | 28.7 | 146.7 | 6.5 | 165.0 | 19.3 | |||||
| 7 | 36.1 | 46.6 | 149.6 | 153.2 | 28.2 | 26.6 | 166.5 | 168.5 | 17.8 | 14.8 | |
| 14 | 48.7 | 53.2 | 147.7 | 151.8 | 32.7 | 46.3 | 162.7 | 166.8 | 18.3 | 21.1 | |
| 28 | 44.5 | 52.5 | 135.5 | 144.4 | 37.9 | 53.6 | 152.5 | 165.5 | 23.3 | 17.6 | |
| PLA/PHB(6:4) | 0 | 61.5 | 151.8 | 16.1 | 170.7 | 27.4 | |||||
| 7 | 53.9 | 61.4 | 154.6 | 154.9 | 28.7 | 25.7 | 171.4 | 170.3 | 32.3 | 25.4 | |
| 14 | 44.4 | 55.1 | 153.6 | 155.0 | 38.4 | 32.5 | 168.6 | 170.7 | 34.0 | 29.3 | |
| 28 | 28.3 | n.d. | 138.2 | 144.2 | 39.0 | 35.7 | 156.9 | 168.3 | 35.7 | 35.7 | |
| PLA/PHB(6:4)/TB | 0 | 28.5 | 146.4 | 9.6 | 165.3 | 23.4 | |||||
| 7 | 33.4 | 47.7 | 149.9 | 153.5 | 23.2 | 28.2 | 167.3 | 169.3 | 25.8 | 24.9 | |
| 14 | 48.0 | 53.5 | 147.9 | 152.7 | 34.1 | 42.2 | 164.3 | 169.4 | 26.5 | 30.9 | |
| 28 | 34.4 | n.d. | 137.4 | 138.9 | 40.9 | 40.1 | 154.7 | 169.1 | 32.9 | 48.5 | |
* ΔHtot is the total enthalpy of each polymer, considering both the crystallization exotherm (when it occurs) and melting endotherm (ΔHtot = ΔHm − ΔHc).