Thermally stimulated currents (TSC) on new and field-aged underground cable material

Field-aged and unaged cable material have been investigated with the TSC technique. Two well defined relaxation modes have been observed for both materials: one high temperature peak (/spl alpha/) at about 115 /spl deg/C that can be related to the melting of the crystalline phase of the polymer and one low temperature peak (/spl beta/) located at about -300 /spl deg/C that can be associated with the glass-rubber transition. Comparison between both sample spectra have shown some noticeable differences. The field-aged material exhibited: (1) lower magnitude ofthe a peak; (2) slightly higher magnitude and temperature shift towards higher temperature for the /spl beta/ peak; (3) higher density and (4) lower melting enthalpy.