Suli Xing

Effects of seawater immersion on water absorption and mechanical properties of GFRP composites

Water absorption behavior and mechanical properties of specimens of an epoxy resin casting and the glass fiber reinforced epoxy matrix composites (GFRP) with two fiber volume fractions (Vf) immersed into artificial seawater were investigated. The composite specimens absorbed less water than the resin casting because water absorption by the matrices was the main way in the composites. The composites with a Vf of 44% absorbed more water than the composites with a Vf of 34% because there were more micropores inside the fiber bundles and capillary paths in the higher fiber volume fractions. Due to the reversible and irreversible changes in the resin casting and the failure of the fiber/matrix interface, the tensile strength, the flexural strength, and the ILSS of the composite specimens after 42 days’ immersion decreased 13%, 43%, 50%, respectively. And the tensile strength, the flexural strength and the ILSS of the specimens after desorption were 97%, 38%, and 43% of the original state, respectively.

A new resin with improved processability and thermal stability

To maintain outstanding thermal stability, amino- and hydroxyl-containing phthalonitrile monomers, 4-(4-aminophenoxy)-phthalonitrile (APN) and 4-(4-hydroxyphenoxy)-phthalonitrile (HPN) were selected and synthesized. Their structures were confirmed by proton nuclear magnetic resonance spectroscopy. Their curing polymers were characterized by Fourier transform infrared spectroscopy. The self-catalytic curing behaviors of the monomers were investigated by differential scanning calorimetry (DSC) at different heating rates. From the results, APN exhibits a higher curing temperature, while HPN exhibits a longer curing time. Then, mixtures of these monomers were investigated by DSC. The result shows that the 50/50 mixture exhibits different autocatalytic behaviors: the curing temperature is lower than that of APN and the curing time of the mixture is shorter than that of HPN. Furthermore, thermogravimetric analysis shows that the polymer from the mixture exhibits higher temperature of 5% weight loss (T5%) and char yield value at 800°C than those of the polymers from each monomer. All these results indicate that the new mixture resin exhibits improved processability with excellent thermal stability, attributed to the synergistic effect between similar monomers; the synergistic effect optimizes the cure reaction kinetics and promotes cross-linking reactions, thereby producing an excellent resin; this approach is a new method for improving the processability without sacrificing thermal stability.

Construction of super-hydrophobic iron with a hierarchical surface structure

Wettability of an iron surface is crucial for the wide applications of iron in practice. In this work, a hierarchical structure highly similar to that of the underside of a bamboo leaf was constructed on an iron surface via the template method and controllable etching. After modification by stearic acid, the iron surface with hierarchical structure showed excellent water repellency, with an average contact angle of 156° and a sliding angle of 3°. X-ray diffraction (XRD) techniques and Fourier transform infrared spectroscopy (FTIR) are applied to examine the chemical components of an iron surface.

Synthesis and Characterization of 4-(2-hydroxyphenoxy) phthalic nitrile

4-(2-hydroxyphenoxy) phthalic nitrile was prepared by the nucleophilic substitution reaction of catechol and 4-nitro phthalic nitrile in DMF with the existence of N2 and K2CO3. The optimal reaction conditions were obtained as follows: the mole ratio of catechol, K2CO3 and 4-nitro phthalic nitrile is 2:1:1, with the quality of the solute concentration of 0.222g/mL and reaction temperature 80°C. Consequently, the yield of final product reached 87.64%, and the structure of the 4-(2-hydroxyphenoxy) phthalic nitrile was characterized by IR, 1H NMR and DSC.

Icephobicity and the effect of water condensation on the superhydrophobic low-density polyethylene surface

A superhydrophobic surface was obtained on a low-density polyethylene (LDPE) substrate using a facile method. The water contact angle and the sliding angle of the superhydrophobic LDPE surface were 155 ± 2° and 4°, respectively. The ice shear stress of the superhydrophobic LDPE surface was 2.08 times smaller than that of the flat LDPE surface. The superhydrophobic surface still showed excellent icephobicity and superhydrophobicity after undergoing a circulatory icing/deicing procedure five times. In addition, water condensation and its effect on the icephobicity of the as-prepared superhydrophobic surface were also studied.