Sensitivity of proton NMR relaxation times in a HTPB based polyurethane elastomer to thermo-oxidative aging

Solid-state 1H NMR relaxometry studies were conducted on a hydroxy-terminated polybutadiene (HTPB) based polyurethane elastomer thermo-oxidatively aged at 80 °C. The 1H T1, T2, and T1ρ relaxation times of samples thermally aged for various periods of time were determined as a function of NMR measurement temperature. The response of each measurement was calculated from a best-fit linear function of the relaxation time vs. aging time. It was found that the T2,H and T1ρ,H relaxation times exhibited the largest response to thermal degradation, whereas T1,H showed minimal change. All of the NMR relaxation measurements on solid samples showed significantly less sensitivity to thermal aging than the T2,H relaxation times of solvent-swollen samples.