Surface Microstructure Study on Corona Discharge-Treated Polyethylene Using Positron Annihilation Spectroscopy.

Area of Science:

• Materials Science
• Surface Science
• Polymer Science

Background:

• Corona discharge treatment is crucial for modifying polymer surfaces, impacting high-voltage cable insulation performance.
• Understanding microstructural and chemical changes is key to predicting material behavior under electrical stress.

Purpose of the Study:

• To investigate the depth profile of microstructural and chemical changes in corona discharge-treated polyethylene (PE).
• To correlate these changes with the performance and degradation of PE insulation materials.

Main Methods:

• Utilized Doppler broadening of positron annihilation spectroscopy (DBPAS) and positron annihilation lifetime spectroscopy (PALS).
• Employed attenuated total reflectance Fourier transform infrared spectra (ATR-FTIR), Raman spectra, and contact angle measurements.
• Employed a slow positron beam for non-destructive depth profiling.

Main Results:

• Increased corona discharge duration led to more oxygen-containing polar groups, enhancing hydrophilicity.
• Mean free volume size decreased slightly, while the degradation layer thickness increased and diffused into the PE matrix.
• A linear S-W plot indicated no change in defect type, with S parameter decreasing and W parameter increasing with corona duration.

Conclusions:

• Corona discharge treatment significantly alters PE microstructure and surface chemistry, affecting hydrophobicity/hydrophilicity.
• Positron annihilation techniques provide effective non-destructive profiling of degradation in insulation materials.
• The findings aid in predicting the performance and longevity of high-voltage cable insulation.