Defect by design: Harnessing the "petal effect" for advanced hydrophobic surface applications.

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.

Study on Microwave Curing of Unsaturated Polyester Resin and Its Composites Containing Calcium Carbonate.

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.