Effects of Interphase Modification and Biaxial Orientation on Dielectric Properties of Poly(ethylene terephthalate)/Poly(vinylidene fluoride-co-hexafluoropropylene) Multilayer Films

Abstract

Recently, poly(vinylidene fluoride) (PVDF)-based multilayer films have demonstrated enhanced dielectric properties, combining high energy density and high dielectric breakdown strength from the component polymers. In this work, further enhanced dielectric properties were achieved through interface/interphase modulation and biaxial orientation for the poly(ethylene terephthalate)/poly(methyl methacrylate)/poly(vinylidene fluoride-co-hexafluoropropylene) [PET/PMMA/P(VDF-HFP)] three-component multilayer films. Because PMMA is miscible with P(VDF-HFP) and compatible with PET, the interfacial adhesion between PET and P(VDF-HFP) layers should be improved. Biaxial stretching of the as-extruded multilayer films induced formation of highly oriented fibrillar crystals in both P(VDF-HFP) and PET, resulting in improved dielectric properties with respect to the unstretched films. First, the parallel orientation of PVDF crystals reduced the dielectric loss from the αc relaxation in α crystals. Second, biaxial stretching constrained the amorphous phase in P(VDF-HFP) and thus the migrational loss from impurity ions was reduced. Third, biaxial stretching induced a significant amount of rigid amorphous phase in PET, further enhancing the breakdown strength of multilayer films. Due to the synergistic effects of improved interfacial adhesion and biaxial orientation, the PET/PMMA/P(VDF-HFP) 65-layer films with 8 vol % PMMA exhibited optimal dielectric properties with an energy density of 17.4 J/cm(3) at breakdown and the lowest dielectric loss. These three-component multilayer films are promising for future high-energy-density film capacitor applications.

Characteristic analysis of biaxially stretched PVDF thin films

“…After stretching, the biaxially oriented PVDF thin film would have balanced piezoelectric activities on the film plane compared to uniaxially oriented one, that would preserve larger piezoelectric coefficient . The highest β‐phase and piezoelectric response ( d 33 ) of biaxially stretched PVDF film was found with stretch ratio of R = 4 × 4 . The aim of this article is to fabricate the PVDF thin film by the equi‐biaxial stretching process in both stretching directions with same stretch ratio; then characterize and evaluate the function of the biaxially stretched PVDF thin film by means of various equipment, and make further comparison with the results of uniaxial stretching under different stretch ratio as well as temperature.…”

Revealing the correlation between molecular structure and dielectric properties of carbonyl‐containing polyimide dielectrics

“…12 Therefore, for the purpose of meeting the requirement of high-temperature capacitors in hostile circumstances, it is of great importance to develop high-temperature resistant polymer dielectrics with superior dielectric properties. [15][16][17] On the other hand, polar polymers such as polyurea and polyurethane, polythoiurea, poly(phenyl oxide), polyimide with reasonably increased dielectric constant and acceptable dissipation factor have been studied by many research groups. [15][16][17] On the other hand, polar polymers such as polyurea and polyurethane, polythoiurea, poly(phenyl oxide), polyimide with reasonably increased dielectric constant and acceptable dissipation factor have been studied by many research groups.…”

“…13,14 Ferroelectric polymers such as poly(vinylidene) fluoride (PVDF) and its random copolymers P(VDF-TrFE) and P(VDF-TrFE-CFE) (TrFE: trifluoroethylene; CFE: chlorofluoroethylene) are of high dielectric constant; however, besides the relatively high dissipation factor, the low curie temperature (about room temperature) and melting points (<170 C) limit their high-temperature applications. [15][16][17] On the other hand, polar polymers such as polyurea and polyurethane, polythoiurea, poly(phenyl oxide), polyimide with reasonably increased dielectric constant and acceptable dissipation factor have been studied by many research groups. [18][19][20][21][22][23][24][25][26][27] The polar groups functioned as permanent dipoles would be beneficial to the enhancement of dielectric constant.…”

Polymer Nanosheet Containing Star‐Like Copolymers: A Novel Scalable Controlled Release System

“…Layer‐multiplying coextrusion of two immiscible polymers generates nanostructured multilayered composite films, and it usually contains hundreds or thousands of polymer thin layers, with thicknesses ranging from the nano‐ to micrometer scales . However, fabrication of free‐standing polymer film with nanoscale thickness from this technique has not been reported.…”

“…The development and optimization of the controlled release systems represents one of the most attractive research topics due to their potential applications in drug delivery, sensors, personal care products, anticorrosion, self-healing coating, Layer-multiplying coextrusion of two immiscible polymers generates nanostructured multilayered composite films, and it usually contains hundreds or thousands of polymer thin layers, with thicknesses ranging from the nano-to micrometer scales. [49][50][51][52][53][54][55][56][57][58] However, fabrication of free-standing polymer film with nanoscale thickness from this technique has not been reported. In this study, we investigate the controlled release property of PNS, which is generated from the coextruded multilayer polymer films (MPFs).…”