Enhanced dielectric properties of sandwich‐structured biaxially oriented polypropylene by grafting hyper‐branched aromatic polyamide as surface layers

Abstract

This work represents multilayer films with sandwich structure by grafting hyper‐branched aromatic polyamide (HBP) on both sides of biaxially oriented polypropylene (BOPP) (HBPBOPPHBP). BOPP serves as the middle layer to offer high breakdown strength and HBP acts as surface layers to boost the dielectric constant. As a result, the dielectric constant increases significantly from 2.2 of control BOPP to 5.5 (almost increased 1.5 times) after grafting 2.06 μm HBP surface layers, while the dielectric loss still remains at a very low level (<0.03). In addition, all HBPBOPPHBP sandwich‐structured films show higher charge energy density than that of unmodified BOPP. For instance, the discharge energy density of HBPBOPPHBP (1‐20‐1) film is up to 2.38 J/cm3 at an applied electric field of 400 kV/mm, which increases about 36% over that of pure BOPP (i.e., 1.75 J/cm3). Meanwhile, charge–discharge efficiency retains about 90%. This work offers a simple strategy to fabricate polymer‐based high performance dielectric composites.

An Overview of Linear Dielectric Polymers and Their Nanocomposites for Energy Storage

“…However, linear dielectrics usually exhibit a relatively low permittivity. For example, the permittivities of commercial biaxially oriented polypropylene (BOPP) [28], polyetherimide (PEI) [29], and polyethylene terephthalate (PET) [30] are 2.2, 3.2, and 3.3, respectively. Therefore, the energy density of these materials will be significantly improved with the increase of the dielectric constant.…”

“…Therefore, BOPP films prepared by melt extrusion and the biaxial stretching of PP show high efficiency. However, due to the intrinsic low permittivity of PP, the BOPP usually exhibits a low energy density (<2 J/cm 3 ) [28]. In addition, the working temperature of BOPP is usually below 105 • C, which significantly limits its application in high-temperature environments [37,38].…”

Efficient approach to produce functional polypropylene via solvent assisted solid-phase free radical grafting of multi-monomers

“…The possible structure and reaction mechanism of AA, MMA and MAH grafting onto PP are discussed in Refs. [2,30,31] and described in Fig. 1.…”

“…Polypropylene (PP) is one of the most widely used polymers in industry, as fiber, film and pipe, because it has many advantageous properties such as easy processing, high chemical resistance, flexibility, low density, adequate mechanical properties and low cost. Due to the low surface energy and lack of reactive functional groups on its molecular chains, PP is not compatible with a wide range of other polymers and fillers and also has printing and adhesion problems [1][2][3][4]. The methods that have been used for obtaining functional modification of PP include chlorination [5], hydroperoxidation [6], hydrogen abstraction from tertiary carbons, followed by ozonolysis [7], in situ copolymerization and grafting copolymerization [8].…”

Largely enhanced energy density of BOPP–OBT@CPP–BOPP sandwich-structured dielectric composites

“…Nonetheless, the energy density was only 2.38 J cm −3 at 400 MV m −1 and the charge–discharge efficiency was less than 60%. 40 In summary, these efforts have achieved some successes in improving the dielectric performance of the PP-based composites. However, there are still some challenges to be addressed before these composites are put into commercial applications.…”