| Rubber compound recipe (pphr) | PET Hardener Percentage | PET (pphr) |
| 0.66 | 0 | 0 |
| 0.589 | 20% | 11.6 |
| 0.552 | 40% | 20.77 |
| 0.47 | 60% | 28.2 |
| 0.443 | 80% | 34.4 |
| 0.39 | 100% | 39.6 |