Small Strain-Induced Abrupt Drop in the Electrical Breakdown Strength of Polypropylene Insulation.
basic_science · Level V
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- Record sourced from PubMed, PMID 41170935.
- Also identified by DOI 10.1021/acs.nanolett.5c04644.
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Abstract
It is commonly acknowledged that the electrical properties of polymer dielectrics remain stable before yielding. However, in this Letter, an abrupt 17.4% decline in the electrical breakdown strength was observed at 4% tensile strain in polypropylene (PP) insulation, which is far below its yielding strain (ε<sub>y</sub>, 16%). In situ scanning electron microscopy was conducted, and microvoids were unexpectedly found, forming at 4% strain, which is inconsistent with the understanding that cavitation only happens near ε<sub>y</sub>. The microvoids lead to higher free volume, increased carrier mobility, and the abrupt decline in the breakdown strength. Furthermore, such critical strain was identified as the elastic limit strain (ε<sub>e</sub>, 3.5%). On that basis, PP samples with suppressed yields and higher ε<sub>e</sub> (5.4%) were prepared with more elastomers. Only a 5.1% decrease in the breakdown strength was observed at 6% strain. This work reveals that suppressing yield and increasing ε<sub>e</sub> can improve the electrical performance stability of semicrystalline dielectrics under mechanical stress.