| Concentration of boric acid (%) | Glass transition temperature (˚C) | ||
| PH PVA | FH PVA | M PVA | |
| 0 | 72 | 79 | 76 |
| 0.5 | 72 | 80 | 79 |
| 1 | 75 | 81 | 78 |
| 1.5 | 80 | 87 | 83 |