Low-κ′ dielectric properties of UV-treated bi-axially oriented polypropylene films

Abstract

A 40 µm multilayer bi-axially oriented polypropylene (BOPP) film, was fabricated by the tenter process and its dielectric response was investigated after applying combined action of UV, humidity and heat. Dissipation factor (tan δ) and relative dielectric constant measurements were performed via the capacitance method for frequencies 20Hz–1 GHz. These results show that the relative dielectric constant (κ′) reduces towards ultra low values (1.8) with an increasing number of applied UV–condensation cycles without any subsequent increase in the dielectric loss. Having no added physical porosity and absence of fluorine atoms, the irradiated BOPP structures offer significant advantages over poly(tetrafluoroethylene) PTFE due to reduced polarization effects, lower dielectric constant values and chemical stability to the adjacent copper or aluminium conductors. Possible application fields are dry type high-voltage capacitors and insulation within electronic components.

Improved Working Temperature and Capacitive Energy Density of Biaxially Oriented Polypropylene Films with Alumina Coating Layers

“…Figure c shows the Al 2 O 3 layer thickness dependences of dielectric constants and dissipation factors from 20 to 125 °C. The dielectric constant and the dissipation factor at 1 kHz for a pure BOPP film at 20 °C are 2.21 and 1.29 × 10 –3 , respectively, consistent with earlier reports. − Due to the dielectric constant of Al 2 O 3 (∼9.0) , higher than BOPP (∼2.21) and the interfacial polarizations possibly existing at the interfaces between BOPP and Al 2 O 3 layers, , the dielectric constant of composite films increases to a higher value of ∼2.39 when the thickness of the Al 2 O 3 layer increases to ∼270 nm (sample ID: AO/BOPP/AO-270). However, with further increasing the thickness of the Al 2 O 3 layer, the defects, surface buckles, and even microcracks will appear during the longtime sputtering; these complicated impact factors should degrade the dielectric constants of the composite films .…”

Dielectric properties of nanopowder emulsions in paraffin oil

“…The relative dielectric constant remains stable at a value of 2.13 for frequencies over 1 kHz. At frequencies below 100 Hz, κ΄ values decrease similarly to previous results for transformer oils [1] and/or other type of organic samples [12,13]. This response relates to the enhanced dielectric losses developing as a result of the dominating low-frequency polarizations.…”

Greatly enhanced breakdown strength and energy density in ultraviolet‐irradiated polypropylene

“…During the UV irradiation, several broken covalent bonds appear in PP, forming a number of charged free radicals with strong chemical activity. These free radicals further combine with oxygen in the air to form carbonyl groups [20,21]. Nevertheless, the rather weak absorption peak intensity of carbonyl group suggests that only few carbonyl groups are generated in PP film under proper UV irradiation time.…”