In‐situ investigation of dielectric properties and reaction kinetics of a glass‐fiber‐reinforced epoxy composite material using dielectric analysis

Abstract

Monitoring the curing behavior of a thermosetting material is a key issue for ensuring a stable manufacturing process (e.g., injection molding). Dielectric analysis (DEA), which is applicable for online‐monitoring, is used to investigate the curing behavior of a glass‐fiber‐reinforced epoxy molding compound. At first, the influences of experimental settings (pressure, temperature, and frequency) on dielectric responses (dielectric loss and ion viscosity) are characterized in a fully crosslinked material. Results show a significant impact of temperature and frequency on dielectric responses. Furthermore, DEA is combined with differential scanning calorimetry (DSC) to investigate dielectric properties depending on crosslink density under non‐isothermal and isothermal conditions. The results show that DEA can detect cure changes only for a crosslink density <80%. Finally, reaction kinetics, which can predict the crosslink density, is derived using DSC and validated through DEA for determining the best suitable kinetic expression for the investigated material. The crosslink density, estimated by reaction kinetics, can be correlated with the dielectric properties.

Effect of gel additives on poly(vinylidene chloride‐co‐acrylontrile)‐based polymer membranes

“…This is possibly associated with the large dipole moment of the carboxyl (C=O) group as well as nitrile (C ≡ N) group in the blend and their strong dipole interactions which might be responsible for the high values of ε″ observed at low frequencies. [ 27 ] Under the influence of an electric field, ions tend to diffuse and migrate along the field appropriately. Since the stainless steel electrode acts as blocking electrodes for ions, they localize at the electrode–electrolyte interface and form a hetero‐charge layer.…”

Characterization of Cure Behavior in Epoxy Using Molecular Dynamics Simulation Compared with Dielectric Analysis and DSC

“…Second, the Kissinger method was applied for determining the activation energy E A and the pre-exponential term A . Equation (9) can be evaluated according to a linear relationship , reported by Yan et al [ 38 ]. Then, the activation energy E A and the pre-exponential term A are determined using Equations (10) and (11): where , R gas is the gas constant, β is the heating rate, T p represents the temperature, and α p is the crosslink density with the index p , which means that the indicated values correspond to the position of the rate peak maximum.…”

“…Second, the Kissinger method was applied for determining the activation energy E A and the pre-exponential term A. Equation ( 9) can be evaluated according to a linear relationship y = a K •x + b K , reported by Yan et al [38]. Then, the activation energy E A and the pre-exponential term A are determined using Equations ( 10) and (11):…”

Research on structure and properties of MWCNT@PDA/polymer matrix composite films with enhanced energy storage performance

“…F I G U R E 3 Cross-sections SEM photos of MWCNT@PDA/PVDF-TrFE composite film (A) and MWCNT@PDA/PVDF-TrFE-CTFE composite film (B) when the MWCNT contents were 0 wt% (1), 0.5 wt% (2), 1.0 wt% (3), 1.5 wt% (4), and 2.0 wt% (5) In order to explain the polarization behavior of the composite film with the change of the electric field intensity better, the ferroelectric test was performed on the two composite films with different filler contents, and the results are shown in Figure 6. When the filler content was 0.5 wt%, the maximum breakdown field strength was 1300 kV/cm.…”

“…Electric energy storage equipment has a high‐power density due to its ultra‐fast charge and discharge capabilities, which can meet the specific needs of various fields, such as artificial muscles, capacitors, and smart skins. [ 1–7 ] As the important part of capacitors, materials with high dielectric constant and its energy storage performance determines the performance of capacitors. A single dielectric material has been difficult to meet the needs of industrialization.…”