Synthesis of TiO2 nanogel composite for highly efficient self-healing epoxy coating

Biohybrid microcapsules based on electrosprayed CS-immobilized nanoZrV for self-healing epoxy coating development

In this work, zirconium vanadate nanoparticles were immobilized into chitosan using a facile electrospraying technique to produce CS-ZrV hybrid microcapsules for the development of a self-healing coating. Upon assessment, hybrid microcapsules possessed desirable properties with a mean particle size of 319 μm, maintaining good thermal stability of ∼55% at 700 °C, and were subsequently incorporated into an epoxy resin to develop a biocompatible self-healing coating, CZVEx, for carbon steel corrosion protection. Scratched samples of self-healing and control coatings were analyzed in a corrosion medium of 3.5 wt% aqueous NaCl. SEM images of the scratched coating sample, after days of immersion, revealed healing of defects through the appearance of an epoxide gel-like substance due to the release of polymeric vanadate that reacted with corrosion agents, resulting in polymerization of vanadium hydrates and subsequent self-healing, validated by the proposed mechanism of self-healing. Electrochemical impedance spectroscopy analysis further confirmed CZVEx coating possessed excellent self-healing capabilities through a significant impedance rise from 4.48 × 105 to 5.52 × 105 (ohm cm2) between the 7th and 14th day of immersion. Furthermore, comparative polarization assessment of coating samples with/without defects indicated the accuracy of EIS for self-healing analysis, and showed the sample with no defect was only 2.6 times more corrosion resistant than the scratched coating, as against bare steel substrate that was 22 times less resistant, revealing superior self-healing anticorrosion properties of the coating.

Low viscosity and low temperature curing reactive POSS/epoxy hybrid resin with enhanced toughness and comprehensive thermal performance

The mechanical and high-temperature resistance properties of epoxy resins cured at low temperatures (Tcuring ≤ 100 °C) are often inferior, and the most toughening modification methods for epoxy resins tend to compromise thermal resistance, which significantly limit the practical applications of it. Therefore, this work reported a low viscosity and low-temperature curing epoxy hybrid resin system (OPEP), adopting E-51 as a resin matrix, liquid anhydride (MHHPA) as a curing agent, tertiary amine (DMBA) as a curing accelerator, and reactive octa-epoxy terminated polyhedral oligomeric silsesquioxane (OG-POSS) as a toughening modifier. Results demonstrated that the OPEP system has excellent processability with low viscosity and long processing window period and satisfies the practical requirements of low-temperature curing. The OG-POSS exhibits superior compatibility and reactivity with the resin matrix, and its addition slightly reduces the Eα of the curing reaction and has a certain promotive effect on the curing of epoxy resin. In addition, the curing reaction rate of the OPEP resin complies with the Šesták-Berggren autocatalytic kinetics model. The impact strength, flexural strength, tensile strength, and elongation at break of the OPEP resin reached a maximum of 15.55 kJ m-2, 121.65 MPa, 90.36 MPa, and 2.48%, representing increases of 55.97%, 3.1%, 64.68%, and 26.51% compared to those of the pure resin, respectively. Notably, due to the heat-resistant inorganic silicon cage structure of OG-POSS, the thermal decomposition temperature (Td5), glass transition temperature (Tg), and heat distortion temperature (THDT) of the OPEP0.02 resin were 313.2 °C, 123.7 °C, and 102.0 °C, showing increases of 13.0 °C, 2.3 °C, and 6.8 °C compared to the pure resin, respectively, which is difficult to achieve for the general thermosetting resin toughening modification method. This research utilized organic-inorganic nanohybrid materials (POSS) to optimize the toughness and thermal stability of the resin in a coordinated manner, providing guidance for the preparation of high-performance epoxy resins that cure at low temperatures.

Enhanced ultra violet resistance of epoxy nanocomposites filled with liquid-like graphene oxide/silicon dioxide nanofluid

The ultra violet (UV) resistance of epoxy resins has been paid more and more attention, and the development of highly efficient UV resistant materials is critical. Therefore, we showed liquid-like graphene oxide (GO)/silicon dioxide (SiO₂)-based derivatives for UV resistance of epoxy resins. To be specific, SiO₂ nanoparticles were deposited in situ on the surface of GO. Subsequently, a black, homogeneous and solvent-free GO/SiO₂ nanofluid was prepared by grafting organosilanes (KH560) and polyetheramines (M2070) on the surface of GO/SiO₂. Furthermore, the solvent-free GO/SiO₂ nanofluid/epoxy resin composites were also prepared. The bending properties before and after UV irradiation of the nanocomposites at room temperature were investigated to reveal the role of the interphase. The toughening mechanism of GO/SiO₂ nanofluid was elucidated by observing the fracture surface. As expected, the loss of bending strength of the resin resulting from UV illumination was efficiently reduced by the GO/SiO₂ nanofluid. This may be attributed to the excellent anti-UV aging properties of GO and SiO₂ nanoparticles. Moreover, the GO/SiO₂ nanofluid can provide excellent bending resistance for epoxy resin both before and after illumination, owing to its great compatibility with epoxy resin by organic chains and hindrance to crack propagation by nano cores.

Synthesis and Characterization of Epoxy-Rich TMOs Deposited on Stainless Steel for Corrosion Applications

Epoxy-trimetallic oxide (epoxy-TMO) coatings of ZrO2:TiO2:ZnO at different compositions were synthesized and used to protect a stainless steel surface. The different TMO compositions were synthesized using the ball-milling method and later dispersed on the polymer matrix. The different characterizations performed on these coatings showed that the epoxy-TMO coating with a ratio of 50:40:10 (wt%) exhibited the highest corrosion resistance, in the order of ~1012 Ωcm2, due to the barrier effect of the distributed particles after 28 days in an aggressive environment (3.5 wt% NaCl solution). The influence of the metal oxides in forming a semiconductor layer produces a capacitor-like behavior, influencing corrosion control via a mass transfer mechanism barrier. The water uptake reveals the effect of each metal oxide in the formation of a physical barrier due to the dispersion mechanism, as well as how the particles function within the polymer matrix.