Epoxy resin reinforced with graphene derivatives: physical and dielectric properties

Hybrid Nanofiller-Enhanced Carbon Fiber-Reinforced Polymer Composites (CFRP) for Lightning Strike Protection (LSP)

The aviation industry relies on lightweight carbon fiber-reinforced polymers (CFRP) for fuel efficiency, which necessitates lightning strike protection (LSP) and electromagnetic shielding due to their electrical insulating characteristics. Traditional metallic meshes used for LSP are heavy and corrosion-prone, prompting the exploration of alternatives. This research showcases CFRP nanocomposites with enhanced LSP properties through the incorporation of graphene nanoplatelets (GNPs) and carbon nanotubes (CNTs). While the enhanced conductivity in the nanofilled epoxy matrix did not impact the overall conductivity of CFRP panels, a significant damage reduction was observed after simulated lightning strike tests. Similar approaches in the literature have also noted this discrepancy, but no attempts to reconcile it have been made. This work provides a framework to explain the damage reduction mechanism while accounting for the modest conductivity improvements in the nanoreinforced CFRPs. Additionally, a simple, nondestructive method to assess surface resin degradation after a lightning strike test is proposed, based on the fluorescence of diphenyl ketones. The discussion is supported by electrical conductivity measurements, damage pattern evaluation using the proposed UV-illumination method, ATR-FTIR, and scanning electron microscopy analysis pre- and postlightning strike simulation.

Ultrasonication Influence on the Morphological Characteristics of Graphene Nanoplatelet Nanocomposites and Their Electrical and Electromagnetic Interference Shielding Behavior

Graphene nanoplatelets (GNPs)/epoxy composites have been fabricated via gravity molding. The electrical and thermal properties of the composites have been studied with variable GNP type (C300, C500, and C750, whose surface areas are ~300, 500, and 750 m2/g, respectively), GNP loading (5, 10, 12, and 15 wt.%), and dispersion time via ultrasonication (0, 30, 60, and 120 min). By increasing the time of sonication of the GNP into the epoxy matrix, the electrical conductivity decreases, which is an effect of GNP fragmentation. The best results were observed with 10-12% loading and a higher surface area (C750), as they provide higher electrical conductivity, thereby preserving thermal conductivity. The influence of sonication over electrical conductivity was further analyzed via the study of the composite morphology by means of Raman spectroscopy and X-ray diffraction (XRD), providing information about the aspect ratio of GNPs. Moreover, electromagnetic shielding (EMI) has been studied up to 4 GHz. Composites with C750 and 120 min ultrasonication show the best performance in EMI shielding, influenced by their higher electrical conductivity.

Preparation and Properties of Hollow Glass Microspheres/Dicyclopentadiene Phenol Epoxy Resin Composite Materials

With the development of the integrated circuit and chip industry, electronic products and their components are becoming increasingly miniaturized, high-frequency, and low-loss. These demand higher requirements for the dielectric properties and other aspects of epoxy resins to develop a novel epoxy resin system that meets the needs of current development. This paper employs ethyl phenylacetate cured dicyclopentadiene phenol (DCPD) epoxy resin as the matrix and incorporates KH550 coupling-agent-treated SiO₂ hollow glass microspheres to produce composite materials with low dielectric, high heat resistance, and high modulus. These materials are applied as insulation films for high density interconnect (HDI) and substrate-like printed circuit board (SLP) boards. The Fourier transform infrared spectroscopy (FTIR) technique was used to characterize the reaction between the coupling agent and HGM, as well as the curing reaction between the epoxy resin and ethyl phenylacetate. The curing process of the DCPD epoxy resin system was determined using differential scanning calorimetry (DSC). The various properties of the composite material with different HGM contents were tested, and the mechanism of the impact of HGM on the properties of the composite material was discussed. The results indicate that the prepared epoxy resin composite material exhibits good comprehensive performance when the HGM content is 10 wt.%. The dielectric constant at 10 MHz is 2.39, with a dielectric loss of 0.018. The thermal conductivity is 0.1872 Wm^-1 k^-1, the coefficient of thermal expansion is 64.31 ppm/K, the glass transition temperature is 172 °C, and the elastic modulus is 1221.13 MPa.

Molecular Understanding of Adhesion of Epoxy Resin to Graphene and Graphene Oxide Surfaces in Terms of Orbital Interactions

The adhesion mechanism of epoxy resin (ER) cured material consisting of diglycidyl ether of bisphenol A (DGEBA) and 4,4'-diaminodiphenyl sulfone (DDS) to pristine graphene and graphene oxide (GO) surfaces is investigated on the basis of first-principles density functional theory (DFT) with dispersion correction. Graphene is often used as a reinforcing filler incorporated into ER polymer matrices. The adhesion strength is significantly improved by using GO obtained by the oxidation of graphene. The interfacial interactions at the ER/graphene and ER/GO interfaces were analyzed to clarify the origin of this adhesion. The contribution of dispersion interaction to the adhesive stress at the two interfaces is almost identical. In contrast, the DFT energy contribution is found to be more significant at the ER/GO interface. Crystal orbital Hamiltonian population (COHP) analysis suggests the existence of hydrogen bonding (H-bonding) between the hydroxyl, epoxide, amine, and sulfonyl groups of the ER cured with DDS and the hydroxyl groups of the GO surface, in addition to the OH-π interaction between the benzene rings of ER and the hydroxyl groups of the GO surface. The H-bond has a large orbital interaction energy, which is found to contribute significantly to the adhesive strength at the ER/GO interface. The overall interaction at the ER/graphene is much weaker due to antibonding type interactions just below the Fermi level. This finding indicates that only dispersion interaction is significant when ER is adsorbed on the graphene surface.

Polyanionic electrically conductive superabsorbent hydrogel based on sodium alginate-g-poly (AM-co-ECA-co-AMPS): Broadband dielectric spectroscopy investigations

In this study, the dielectric behavior of polyanionic electrically conductive superabsorbent hydrogel based on sodium alginate-g-poly(AM-co-ECA-co-AMPS) was investigated by broadband dielectric spectroscopy (BDS). The dielectric spectra obtained from -70 to 70 °C showed a superposition of three distinctive processes, electrode polarization, charge carrier's transport, and a molecular relaxation process. These dynamic processes were further analyzed along with the effect of both temperature and reduced graphene oxide (rGO) content. The development of a clear electrochemical double layer (ECDL) at the electrode/hydrogel interface strongly supports its possible application in supercapacitors' forms of energy storage. TGA, DSC, rheology, and electrochemical properties were studied. Furthermore, when the composite hydrogel with rGO content of 2.5 % was assembled into a symmetric supercapacitor, it displayed a specific capacitance of 756 F.g^-1 at 1 A.g^-1 and 704 F.g^-1 after 5000 cycles with high capacitance retention of 93.2 %. The superior conductivity and porous structure of the rGO composite hydrogel are credited with the hydrogel's excellent electrochemical capabilities.

Evaluation of augmented thermal, thermo-mechanical, mechanical properties of nano alumina reinforced TGDDM epoxy nanocomposites

N,N′-Tetraglycidyldiaminodiphenyl methane (TGDDM) was reinforced with various weight fractions (0.5, 1, and 1.5 wt%) of amine functionalized nano alumina (F-Al) were cured with diaminodiphenyl-methane (DDM). FT-IR analysis revealed that formation of functionalized nano alumina (F-Al) structure, was brought about via coupling agent APTES. Furthermore, the morphology of TGDDM epoxy nanocomposites was studied using X-ray Diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), microscopic analysis and an atomic force microscope (AFM). We found a bonding relationship between TGDDM epoxy and F-Al in TGDDM/F-Al nanocomposites It was interesting to note that the values of tensile, flexural and impact strength of 1 wt% F-Al reinforced TGDDM epoxy nanocomposites were found to be 141.5, 192.5 MPa, and 92.4 J/m2, respectively., which resulted in a substantial improvement in the dynamic mechanical analysis (DMA) to 4.3 and 5.5 for 0.5 and 1 wt% F-Al reinforced TGDDM epoxy nanocomposites and the glass transition temperature (Tg) increased from 210°C to 225°C as the F-Al content increased. The initial degradation temperature (IDT) of 0.5, 1, and 1.5 wt% F-Al reinforced TGDDM epoxy nanocomposites were significantly enriched to 328°C, 345°C, and 335°C respectively from 290°C of neat (TGDDM) epoxy matrix. Likewise, the char yield for the neat (TGDDM) epoxy matrix was 13% and that for 0.5, 1, and 1.5 wt% F-Al reinforced TGDDM epoxy nanocomposites were 17%, 25%, and 20% respectively. It is feasible to state unequivocally that considerable F-Al diffusion within the TGDDM epoxy can only occur at low weight percentages. The results clearly showed that F-Al reinforced TGDDM epoxy nanocomposites may be investigated for advanced high performance industrial engineering applications.