Methyl Methacrylate-co-glycidyl Methacrylate-Based Dielectric Films with High Breakdown Strength and Discharge Energy Density Tailored by PVDF.

Linear dielectric polymers are potential candidates for electrostatic capacitors due to their high breakdown strength, high efficiency, and low dielectric loss. In this work, a novel poly (vinylidene fluoride) (PVDF) tailored linear PMMA-co-GMA (MG) copolymer-based all-organic dielectric film with high breakdown strength and discharge energy density was prepared by the solution blending method. Compared with the PMMA homopolymer, the MG copolymer behaved with a higher energy density (5.6 J/cm3) since the GMA component bestowed higher polarity and yielded deep traps for the copolymer. On the other hand, the introduction of PVDF into MG further improved the dielectric constant and overcame the brittleness of MG films. When the concentration of PVDF was 30 wt %, the MG/PVDF film exhibited a high discharged energy density of 10.8 J/cm3 at 600 MV/m with a 78.7% discharge efficiency, which was 2.5 times that of pure PVDF (4.3 J/cm3 at 320 MV/m) and 1.9 times that of pure MG (5.6 J/cm3 at 460 MV/m). The improvement in energy storage performance might be ascribed to the excellent thermodynamic miscibility and hydrogen bond interaction between the linear MG copolymer and the ferroelectric PVDF. This research provides a new and feasible strategy for designing all-organic dielectric films with high energy density for energy storage applications.

Crosslinking modification and hydrogen bonding synergy to achieve high breakdown strength and energy density of PMMA-co-GMA/PVDF dielectric composite films.

Polymer-based dielectric materials have been used in film capacitors due to their rapid charge-discharge rate, lightness, and low cost. Nevertheless, the energy storage properties of these dielectric films were limited by their weak polarization ability and low discharge energy density. Herein, the solution casting method was used to prepare all-organic crosslinked composite films using linear methyl methacrylate-co-glycidyl methacrylate (MG) as the matrix and ferroelectric poly(vinylidene fluoride) (PVDF) as the organic filler. The crosslinked MG networks can enhance the breakdown strength, restrain dielectric loss, and keep high discharge efficiency. What's more, the presence of PVDF can compensate for the low electrical displacement, improve the permittivity, and overcome the brittleness of the crosslinked films. The optimal all-organic crosslinked dielectric film exhibited an ultrahigh breakdown strength of 800 MV m-1 and a high efficiency of 77.4%. The maximum energy density of the composite film reached up to 12.1 J cm-3, which was nearly 120% higher than the energy density of 5.6 J cm-3 of the pure MG film. The enhancement in energy storage properties is ascribed to the synergistic effects of chemical crosslinking and hydrogen bonding. This study offers a feasible method for all-organic polymer films to fabricate energy storage equipment.

All-organic PVDF-based composite films with high energy density and efficiency synergistically tailored by MMA-co-GMA copolymer and cyanoethylated cellulose.

All-organic polymer dielectric films have been widely used for different electrical devices in recent years. However, their development is impeded by low Ue and large device volume. In the present paper, polyvinylidene fluoride (PVDF) composite dielectric materials, with high energy density (Ue) and energy efficiency (η), were prepared through the synergistic effect of a new MMA-co-GMA (MG) copolymer and cyanoethylated cellulose. MG was miscible with PVDF, which reduced the dielectric loss (tan δ) and improved the η of PVDF due to the linear structure and the hydrogen bonding interaction with the epoxy groups for MG. To further enhance the Ue of the dielectric films, cyanoethylated cellulose (CR-C) was added as a third component into the PVDF composite matrix to improve the Ue. The deep trap effect of hydrogen bonds between PVDF/MG and CR-C improved the electric breakdown strength (Eb) of the three-phase composite films from 440 MV m-1 to 640 MV m-1. Moreover, the high polarization of cyanoethylated cellulose can significantly improve the Ue (24.43 J cm-3) of the three-phase composite dielectric film, and the efficiency can be maintained above 75% at 640 MV m-1. This research provides a new idea for the manufacturing of homogeneous and stable all-organic PVDF dielectric composite films based on the hydrogen bonding construction strategy.

Grafting Modification of the Reactive Core-Shell Particles to Enhance the Toughening Ability of Polylactide.

In order to overcome the brittleness of polylactide (PLA), reactive core-shell particles (RCS) with polybutadiene as core and methyl methacrylate-co-styrene-co-glycidyl methacrylate as shell were prepared to toughen PLA. Tert-dodecyl mercaptan (TDDM) was used as chain transfer agent to modify the grafting properties (such as grafting degree, shell thickness, internal and external grafting) of the core-shell particles. The introduction of TDDM decreased the grafting degree, shell thickness and the Tg of the core phase. When the content of TDDM was lower than 1.15%, the RCS particles dispersed in the PLA matrix uniformly-otherwise, agglomeration took place. The addition of RCS particles induced a higher cold crystallization temperature and a lower melting temperature of PLA which indicated the decreased crystallization ability of PLA. Dynamic mechanical analysis (DMA) results proved the good miscibility between PLA and the RCS particles and the increase of TDDM in RCS induced higher storage modulus of PLA/RCS blends. Suitable TDDM addition improved the toughening ability of RCS particles for PLA. In the present research, PLA/RCS-T4 (RCS-T4: the reactive core-shell particles with 0.76 wt % TDDM addition) blends displayed much better impact strength than other blends due to the easier cavitation/debonding ability and good dispersion morphology of the RCS-T4 particles. When the RCS-T4 content was 25 wt %, the impact strength of PLA/RCS-T4 blend reached 768 J/m, which was more than 25 times that of the pure PLA.