^1H NMR tests on damaged and undamaged XLPE and SiR samples

Abstract

Cross-linked polyethylene (XLPE) and silicone rubber (SiR) samples were subjected to a high-voltage AC stress plane–plane configuration and inclined plane test, respectively. The voltage was applied such that discharge was observed across the surface of the XLPE test sample for several hours and for visible damage to occur on SiR samples also after several hours. Selected stressed samples together with virgin samples from the same manufactured batch were tested using nuclear magnetic resonance (NMR) spectroscopy. Specifically, ^1H NMR spin–lattice (T(1)) and spin–spin (T(2)) relaxation time measurements were employed to examine potential changes in the chemical bonding of undamaged and damaged XLPE and SiR samples. Preliminary results show that there may be a moderate increase in the T(1) and T(2) values of the damaged samples in comparison with the undamaged ones. This raises the possibility that NMR can be a useful additional experimental tool in characterising material degradation.

Keywords

• silicone rubber
• bonds (chemical)
• XLPE insulation
• nuclear spin-lattice relaxation
• proton magnetic resonance
• spin-spin relaxation
• discharges (electric)
• undamaged XLPE
• SiR samples
• damaged samples
• damaged XLPE
• inclined plane test
• XLPE test sample
• visible damage
• virgin samples
• nuclear magnetic resonance spectroscopy
• stressed samples
• ^1H NMR tests
• high-voltage AC stress plane-plane configuration
• cross-linked polyethylene
• silicone rubber samples
• discharge
• ^1H NMR spin-lattice relaxation time measurements
• ^1H NMR spin-spin relaxation time measurements
• chemical bonding