Chitosan toughened epoxy resin by chemical cross-linking: Enabling excellent mechanical properties and corrosion resistance

There is a growing demand for the development of epoxy resin modified with biomaterials, aiming to achieve high toughness. Herein, chitosan crosslinked epoxy resin (CE) was synthesized by diisocyanate as a bridge. With 4,4'-diamino-diphenylmethane (DDM) as the curing agent, thanks to the unique cross-linking structure of the CE resin and the presence of carbamate groups, the cured CE/DDM exhibited superior properties compared to commercially available epoxy resin (E51). The tensile strength of the cured CE-3/DDM reached 90.17 MPa, the elongation at break was 11.2 %, and the critical stress intensity factor (KIC) measured 1.78 MPa m1/2. These values were 21.4 %, 151.6 %, and 81.6 % higher than those of the cured E51/DDM, respectively. It is worth noting that the addition of biomass material chitosan did not reduce the thermal stability of the resin. Additionally, the CE coatings on the metal substrate exhibited exceptional corrosion resistance, as evidenced by higher impedance values in electrochemical impedance spectroscopy (EIS) and polarization voltages in the Tafel curve compared to those of the E51 coating. This study opens up a novel approach to modifying epoxy resin with biomass materials with high toughness and corrosion resistance, without sacrificing other performance.

Hydrophobicity and corrosion resistance of waterborne fluorinated acrylate/silica nanocomposite coatings

This study aims to improve the hydrophobic properties and corrosion resistance of fluorinated acrylate coatings. The surface of nano-SiO2 was modified by the silicone coupling reagent (KH-570), and the reactive functional groups were introduced to modify fluorinated acrylates. The functionalized SiO2-modified waterborne fluorinated acrylate emulsion was prepared by free polymerization with dual initiators. The structure of the polymer was analyzed by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectro-meter (1H-NMR), X-ray photoelectron spectroscopy (XPS) and Waters gel chromatography (GPC). The properties of the films and coatings were analyzed by contact angle, atomic force microscopy, scanning electron microscopy, and electrochemical analysis. The results showed that the contact angle reached 120° when the SiO2 content was 3%, the electrochemical impedance value reached 1.49 × 107 Ω·cm2, and the pencil hardness was 3H.

Preparation and Characterization of Waterborne UV Lacquer Product Modified by Zinc Oxide with Flower Shape

In this paper, the waterborne UV lacquer product (WUV) was used as the main raw material, zinc oxide (ZnO) was used as the additive, and the stearic acid as the surface modifier. According to the method of spraying coating on the surface of poplar wood (Populus tomentosa), a simple and efficient preparation method was carried out to generate a super-hydrophobic surface and enhance the erosion resistance of the coating. By testing, the contact angle (CA) of water on the coating surface can reach 158.4°. The microstructure and chemical composition of the surface of coatings were studied by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction (XRD). The results showed that under acidic conditions, the non-polar long chain alkyl group of stearic acid vapor molecule reacted with the hydroxyl group in acetic acid, the metal ions of the ZnO were displaced to the stearic acid and generated globular zinc stearate (C₃₆H₇₀O₄Zn). The hydrophobic groups –CH₃ were grafted to the surface of zinc stearate (ZnSt2) particles and the micro/nano level of multistage flower zinc stearate coarse structure was successfully constructed on the surface of poplar wood, which endowed it with superhydrophobic properties. It is shown that the coating has good waterproof and erosion resistance.