The Role of Film Processing in the Large-Area Dielectric Breakdown Performance of Nano-Silica-BOPP Films

Ilkka Rytöluoto,Mikka Karttunen,Mikael Ritamäki,Kari Lahti

doi:10.5324/nordis.v0i24.2286

Ilkka Rytöluoto, Mikka Karttunen + Show 2 more

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https://doi.org/10.5324/nordis.v0i24.2286

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Abstract

This paper summarizes the effects of various compositional, structural and film processing factors on the breakdown behavior of laboratory- and pilot-scale melt-compounded bi-axially oriented polypropylene (BOPP) nanocomposite films with silica fillers. A selfhealing multi-breakdown measurement approach has been extensively utilized for large-area breakdown characterization of a large number of material variants from different processing trials. The results suggest that although the optimum level of silica presumably resides at the low fill-fraction range (~1 wt-%), the silica content itself is not the only determining factor, as compounds with equal silica content were found to exhibit large differences in the breakdown properties depending on the compounding and film processing steps. Dispersion quality and filler agglomeration (in both the nm- and μm-scale) appear to be of great importance. Indications of possible interaction between nano-silica and co-stabilizer Irgafos 168 are also presented. Overall, the laboratory- and pilot-scale film processing trials suggest that up-scaling of the polymer nanocomposite production is sensible with traditional melt-blending technology, although further development and optimization of nanocomposite formulations and processing is necessary.

Highlights

In recent years, an increasing amount of research on dielectric polymer nanocomposite (PNC) films for nextgeneration high-energy-density capacitor applications has emerged and improvements in properties such as dielectric breakdown strength are strongly aspired for [1]
As the dielectric breakdown performance of polymer-based thin films is largely dependent on various processing- and material-related aspects [5], [6], a thorough understanding of the underlying factors and optimization of the film processing parameters are crucial in order to achieve improved breakdown strength in practical insulation systems
As discussed in [3], [4], Figure 2a clearly shows that an increase in silica content reduces the breakdown performance in the >5 % breakdown probability region in comparison to the unfilled reference bi-axially oriented polypropylene (BOPP) and leads to a concurrent improvement of the breakdown distribution homogeneity

Summary

Introduction

An increasing amount of research on dielectric polymer nanocomposite (PNC) films for nextgeneration high-energy-density capacitor applications has emerged and improvements in properties such as dielectric breakdown strength are strongly aspired for [1]. As the dielectric breakdown performance of polymer-based thin films is largely dependent on various processing- and material-related aspects [5], [6], a thorough understanding of the underlying factors and optimization of the film processing parameters are crucial in order to achieve improved breakdown strength in practical insulation systems. Provided that a potential PNC formulation is developed, it is important to consider whether or not it is possible to up-scale the film production process towards large-scale industrial manufacturing. A number of SiO2-BOPP PNC film production trials were carried out in order to study the effects of various processing parameters on the breakdown performance.

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