RESUMEN
HYPOTHESIS: In the interfacial wetting boundary, the superhydrophobic surface is often damaged, and the anisotropic wettability of its surface has attracted many researchers' attention. The "petal effect" surface has typical anisotropic wettability. We predict that under the dual conditions of structural defects and high impact velocity, the "petal effect" becomes more adhesive on the surface. EXPERIMENTS: This study refers to the droplet state on rose petals, structural defects were constructed on the superhydrophobic surface. This paper studies the influence of macro-structural defects on the wettability change from natural to bionic "lotus effect" to "petal effect" in both static and dynamic angles. FINDINGS: Macro defects significantly change the static contact angle of the superhydrophobic surface. The higher the impact velocity of the droplet, the higher the energy dissipation of the "petal effect" surface (DSHS), which improves the adhesion of the surface to the droplet and prolongs the contact time. It is found that the defect structure and high impact velocity will directly affect the deposition and desorption of droplets on the superhydrophobic surface, and they are both essential. This wetting dynamic law is very likely to be helpful in the quantitative design of defect structure scale for dynamic desorption of droplets on superhydrophobic surfaces.
RESUMEN
Microwave curing technology has been widely used in resin and its composite materials. In order to study its effect for curing unsaturated polyester resin (UPR) composites containing calcium carbonate (CaCO3) filler, this paper first investigated the influence of microwave power and microwave irradiation time on the curing characteristics of UPR. Then, CaCO3 particles were added to the UPR to investigate the microwave curing effect of the UPR composites containing the CaCO3. The results showed that microwave irradiation could heat the UPR sample evenly, and rapidly cause the chain growth reaction, thus greatly shortening the curing time. The curing degree and products of the samples after microwave curing were consistent with that of the thermal curing. The addition of CaCO3 particles could increase the heating rate of the UPR composites, which would accelerate the curing rate of the UPR. However, higher microwave power could lead to pore defects inside the UPR composites with higher CaCO3 content, resulting in a lower strength. Thus, the compactness of the samples should be improved by reducing the microwave power and prolonging the microwave treatment time.
RESUMEN
An organic coating is commonly used to protect metal from corrosion, but it is prone to failure due to microcracks generated by internal stress and external mechanical action. The self-healing and self-lubricating achieved in the coating is novel, which allows an extension of life by providing resistance to damage and repair after damage. In this study, a new approach to microencapsulating bifunctional linseed oil with polyurethane shell by interfacial polymerization. Moreover, the self-healing and self-lubricating coatings with different concentrations of microcapsules were developed. The well-dispersed microcapsules showed a regular spherical morphology with an average diameter of ~64.9 µm and a core content of 74.0 wt.%. The results of the salt spray test demonstrated that coatings containing microcapsules still possess anticorrosion, which is improved with the increase of microcapsules content, after being scratched. The results of electrochemical impedance spectroscopy showed a |Z|f=0.01Hz value of 104 Ω·cm2 for pure epoxy coating after being immersed for 3 days, whereas the coating with 20 wt.% microcapsules was the highest, 1010 Ω·cm2. The results of friction wear showed that the tribological performance of the coating was enhanced greatly as microcapsule concentration reached 10 wt.% or more, which showed a 86.8% or more reduction in the friction coefficient compared to the pure epoxy coating. These results indicated that the coatings containing microcapsules exhibited excellent self-healing and self-lubricating properties, which are positively correlated with microcapsules content.
