Synthesis and Characterization of Novel Polypropylene Systems for High Energy Capacitor Applications
Open Access
- Author:
- Matsuyama, Yuichi
- Graduate Program:
- Materials Science and Engineering
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- None
- Committee Members:
- T C Chung, Thesis Advisor/Co-Advisor
Tze Chiang Chung, Thesis Advisor/Co-Advisor - Keywords:
- non-polar polymers
hydroxylation
dielectric constant
long chain branched polypropylene
film capacitor - Abstract:
- High breakdown strength and high permittivity are two essential properties in a film capacitor for high energy storage applications. Polypropylene is a leading material in this area with a high breakdown strength (>640 MV/m) and a low energy loss (Dissipation factor at 1 kHz, <0.02). However, its low melt strength limits the choice of thermal processing techniques. The melt strength can be improved by the introduction of long chain branches via a synthetic approach using a T-reagent. In this study, the efficiency of a T-reagent was improved through a low temperature (below 37 °C) reaction and a synthesis of a long chain branched polymer containing polyethylene backbone and polypropylene branches (PE-BSt-PP). The low temperature reactions showed improvement in the branch/pendant styrene ratios, and the PE-BSt-PP approach utilized all of the T-reagent present. Comparisons of linear and branched polypropylene exhibited a reduction in fatal defects in long chain branched polypropylene and increase in the overall stability of the film, indicated by the increases in Weibull alpha and beta values. Hydroxylation improved the permittivity of polypropylene by a factor of 2 and non-polar polybutadiene by a factor of 10. Compared to the unmodified 1,4-polybutadiene, the dielectric constant of the hydroxylated 1,4-polybutadiene containing alternative vinyl alcohol and ethylene units in the backbone was increased by nearly an order of magnitude at 50 °C and 20 to 200 Hz, due to parallel OH dipole orientation. Investigation of different polymers with various concentrations of hydroxyl groups revealed the correlations between the dielectric constant, concentration of hydroxyl group, structure, and glass transition temperature.