| ASTM Test | Physical Properties | Fibralon 4840 |
| F 37 | Sealability ml/hr Nitrogen 30psi, 3000 psi load | 0.002 |
| F 38 | Creep Relaxation % | 5.8 |
| F 36 | Compressibility % | 12.8 |
| F 36 | Recovery % | 52 |
| D-638 | Tensil Strength, PSI | 2370 |
| D-638 | Elongation % | 138 |
| D-1708 | Elongation Modulus at 100% PSI | 0 |
| D-792 | Specific Gravity | 2.02-2.09 |
| D-149 | Dielectric Strength, volts/mil | 260.8 |
| F-433 | Thermal Conductivity- BTU-in/hr -ft(2) deg F | 3.42 |
| D-621M | Deformation under load (1000 lb.), | 0.2 |