Effect of film structure and morphology on the dielectric breakdown characteristics of cast and biaxially oriented polypropylene films

Morphology Development, Structure and Dielectric Properties of Biaxially Oriented Polypropylene

“…An inverse trend between surface roughness and breakdown strength was also observed (not shown), with the results being consistent with those presented by Fujiyama et al for a variety of surface-roughened BOPP films [23]. Further analysis and discussion on processing-structure-breakdown relationships is omitted from this paper and will be presented elsewhere [5].…”

“…However, surprisingly few systematic studies have been published on the dependence of dielectric properties on the base PP properties, film processing parameters and the resulting morphology-such knowledge would provide further means to optimize dielectric performance of BOPP capacitor films. This paper outlines our recent study [5] on processingstructure-dielectric property relationships of two capacitor-grade isotactic PP (iPP) materials which were extruded into 200-500 µm cast films using three different extruders and subsequently biaxially oriented using a laboratory sheet stretching machine with two different stretch-ratios to produce BOPP films in the 10-15 µm thickness range. Extensive material characterization was performed for the cast and biaxially oriented film samples, including: (i) crystalline structure, (ii) melting behavior, (iii) surface roughness, haze, orientation and cross-sectional structure, (iv) large-area DC dielectric breakdown performance, and (v) permittivity and dielectric loss.…”

Silica-Polypropylene Nanocomposites for Film Capacitors: Structure–Property Studies and the Role of Biaxial Stretching Conditions

“…It is well known that the initial cast film morphology plays a significant role in the morphology formation upon biaxial stretching [6]. Mixed type α/β-form crystalline structure was confirmed by DSC analysis for each cast film, as is exemplified in Figure 1 for a 4.5 wt-% silica-PP and unfilled reference PP compounds.…”

“…Room temperature large-area DC breakdown characteristics of the biaxially stretched films were measured using a selfhealing breakdown method detailed in [5], [6]. Test capacitors with active area of 81 cm 2 were assembled by sandwiching the sample film between two sheets of commercial metallized BOPP film, the metallized surfaces of which were facing towards the sample film.…”

Compounding, Structure and Dielectric Properties of Silica-BOPP Nanocomposite Films

“…Next-generation PP-silica nanocomposites to be utilized in DC cables and capacitors are currently being developed in the European project GRIDABLE. It is known from our previous studies that optimized nanoparticle surface functionalization, pre-mixing, compounding and film manufacturing practices under clean processing conditions are pivotal in achieving highdielectric-performance biaxially oriented thin films [3,12,13]. Thus, as a preparatory stage for a forthcoming industrial-scale material production trial, silica-BOPP films manufactured in laboratory scale are currently being studied for establishing optimized material formulations and processing procedures.…”