Modifications of Gamma poly (vinylidene fluoride) (γ-PVDF) films by high-energy electron beam irradiation

A novel in situ sample environment setup for combined small angle x-ray scattering (SAXS), wide-angle x-ray scattering (WAXS), and Fourier transform infrared spectrometer (FTIR) simultaneous measurement

Developing the synchrotron radiation experiment method based on combined technology offers more information on the formation mechanism of new materials and their physical and chemical properties. In this study, a new small-angle x-ray scattering/ wide-angle x-ray scattering/ Fourier-transform infrared spectroscopy (SAXS/WAXS/FTIR) combined setup was established. Using this combined SAXS/WAXS/FTIR setup, x-ray and FTIR signals can be obtained simultaneously from the same sample. The in situ sample cell was designed to couple two FTIR optical paths for the attenuated total reflection and transmission modes, which greatly saved the time of adjusting and aligning the external infrared light path when switching between the two modes with good accuracy. A transistor-transistor logic circuit was used to trigger the synchronous acquisition from the IR and x-ray detectors. A special sample stage is designed, allowing access by the IR and x-ray with temperature and pressure control. The newly developed, combined setup can be used to observe the evolution of the microstructure during the synthesis of composite materials in real-time at both the atomic and molecular levels. The crystallization of polyvinylidene fluoride (PVDF) at different temperatures was observed. The time-dependent experimental data demonstrated the success of the in situ SAXS, WAXS, and FTIR study of the structural evolution, which is feasible to track the dynamic processes.

Concurrent Enhancement of Breakdown Strength and Dielectric Constant in Poly(vinylidene Fluoride) Film with High Energy Storage Density by Ultraviolet Irradiation

Polyvinylidene fluoride (PVDF) film with high energy storage density has exhibited great potential for applications in modern electronics, particle accelerators, and pulsed lasers. Typically, dielectric/ferroelectric properties of PVDF film have been tailored for energy storage through stretching, annealing, and defect modification. Here, PVDF films were prepared by the solution casting method followed by an ultraviolet (UV) irradiation process, with special emphasis on how such treatment influences their dielectric and energy storage properties. Upon UV irradiation, the dielectric constant and breakdown strength of the PVDF film were enhanced simultaneously. A high energy density of 18.6 J/cm³, along with a charge-discharge efficiency of 81% at 600 MV/m, was achieved in PVDF after exposure to UV for 15 min. This work may provide a simple and yet effective route to enhance energy storage density of PVDF-based polymers.

Mapping the scientific research on the ionizing radiation impacts on polymers (1975–2019)

A bibliometric approach allowed us to study the global research trend on the impact of ionizing irradiations on polymers from 1975 to 2019. The investigation revealed 1,015 publications with growing interest since 1990. The research is split into three main categories: polymer science, nuclear science technology, and chemistry physical. The three main ionizing irradiations studied in this research are gamma, electron beam, and X-ray irradiations. The impact of ionizing irradiations on polymers under gamma irradiation is the most commonly studied field with 578 publications among the 1,015 publications. Electron beam irradiation is the second most studied field followed by X-ray irradiation. Whatever the irradiation modalities, publications focus on material degradation and material improvement studies.

Gamma Radiation-Induced Unsaturated P(VDF-CTFE) Membranes with Improved Mechanical Properties

Poly(vinylidene fluoride-chlorotrifluoroethylene) (P(VDF-CTFE)) membranes were prepared by drop-casting with tetrahydrofuran (THF), and were then radiated by a low dose of gamma radiation without any other reagents. The apparent colour of the freshly prepared film was a semi-transparent white, which gradually darkened and finally turned black after 10.2kGy gamma radiation. Meanwhile, the yield and breaking strength of the membrane both improved. X-Ray diffraction (XRD) spectra showed that the structure of the microcrystal of the irradiated P(VDF-CTFE)-THF membrane was not changed. FT-IR analysis showed that the structure of the newly formed double bonds was dominated by –CF2–CF=CH–CF2–, which was formed by both dehydrofluorination and dehydrochlorination. This structure was further confirmed by 1H NMR spectra. The intermediates, such a radical-containing double bonds (–(CF=CH)n–C•F–) formed in this process were traced by electron paramagnetic resonance (EPR) spectroscopy. The thermal and mechanical properties were studied by gel permeation chromatography (GPC), thermogravimetric analysis (TGA), stress–strain and dynamic mechanical analysis (DMA), and all the changes of microstructure and optimization of apparent properties were not found in the corresponding membrane prepared by a solution-cast method with ethyl acetate (EtOAc). Therefore, this paper briefly analyses the probable mechanism of using low dose of gamma radiation to improve the mechanical properties of the P(VDF-CTFE) film prepared with THF.

Improved battery performance contributed by the optimized phase ratio of β and α of PVDF

Inorganic salts (LiCl) were induced to improve the ratio of β and α of PVDF by the solution method. The vibrational spectra of PVDF polymorphic polymers were obtained by Fourier transform infrared spectroscopy (FTIR), and the results showed that the ratio of β and α of pristine PVDF was elevated from 43.66% to 53.27%. A small amount of LiCl grains was detected to be decorated on the surface of LiCl-involved electrodes by the SEM and EDS tests. The rate capability of the modified samples was evaluated when charge-discharged at 5C. The capacity of the 1/10LiCl@PVDF samples remained at a high level of 71.64% when charge-discharged at 5C, which was much higher than the value of 54.66% for pristine samples. The results of the CV and EIS tests revealed that the electrochemical polarization increasing rate and charge transfer resistance of the 1/10LiCl@PVDF samples were smaller than those of the pristine PVDF samples.

Inorganic salts (LiCl) were induced to improve the ratio of β and α of PVDF by the solution method.