Probing micro-scale charge migration of polycrystalline polypropylene under high temperatures

Area of Science:

• Materials Science
• Polymer Science
• Electrical Engineering

Background:

• Dynamic charge transport in polymers is crucial for insulation performance.
• Understanding nanoscale charge migration mechanisms in polymer composites at high temperatures remains challenging.

Purpose of the Study:

• To investigate charge migration mechanisms in polypropylene (PP) microregions using Kelvin probe force microscopy (KPFM).
• To explore the influence of temperature and phase structure (α-PP vs. β-PP) on charge transport and dielectric properties.

Main Methods:

• Fabrication of PP films via solution crystallization.
• Utilizing KPFM to analyze charge accumulation, dissipation, and migration in microregions.
• Implementing an in-situ heating system to study temperature-dependent charge behavior.
• Developing an in-situ micro-region dielectric constant testing method.

Main Results:

• Charge accumulation and dissipation rates follow an exponential law.
• The charge injection barrier is lower in α-PP than β-PP, influenced by surface conductivity.
• Charge transport rate increases with electric field strength and temperature.
• The β phase's irregular structure and shallow traps enhance charge transport at high temperatures.
• Dielectric constant of β-PP is slightly higher, with a reverse increase above 100 °C attributed to interface polarization and dipole orientation.

Conclusions:

• Microregion charge behavior in PP is significantly influenced by temperature and crystalline phase.
• The findings provide critical insights into polymer dielectric performance at elevated temperatures.
• The developed in-situ methods enable detailed analysis of microscale dielectric phenomena.