A STUDY ON THE RELATION BETWEEN MORPHOLOGICAL AND CHEMICAL CHANGES AND WETTABILITY MODIFICATION OF POLYETHERSULFONE SURFACE AFTER IRRADIATION WITH A PULSED KrF LASER

Laser irradiation is used for surface modification of polymers aiming to improve their properties for different applications. The wettability of a polymeric surface can significantly affect its performance for biological applications. In this paper, the interaction of high-energy KrF laser photons in the two above- and below-threshold regimes with polyethersulfone polymer is studied. The role of morphological and chemical changes of the irradiated polymer and their correlation in the modification of the wetting property of this polymer is investigated. The obtained results show that the morphological parameter of surface roughness is the dominant mechanism in the below-threshold regime, while in the above-threshold region, the competition between this parameter and the carbonization amount of the surface determines the final hydrophilic response.

Non-wettable antibacterial thin film: PS/Aloe vera and PS/Acalypha indica

The water and liquid repelling materials due to their low surface energy and specific nanometer and micrometer scale roughness have particular interest due to the great variety of potential applications ranging from self-cleaning surfaces to microfluidic devices. Natural plant-based polymer hydrophobic coatings have several engineering and biomedical applications. In this study, natural plants such as Aloe vera and Acalypha indica were used for preparation of polystyrene hydrophobic film by the dip-coating method. The effects of Aloe vera and Acalypha indica extract on the morphological, structural, optical and antibacterial properties of as-prepared polystyrene thin films were studied. FTIR spectra were carried out to ascertain the presence of functional groups in the prepared polymeric film. Contact angle measurement showed that the PS/ Aloe vera has higher anti-wetting property (CA = 112°) compared to PS/ Acalypha indica (CA = 104°), which could be confirmed by the surface morphology analysis. Furthermore, the effective antibacterial activity against Klebsiella pneumoniae and Staphylococcus aureus was compared by agar-well diffusion method. The observed result reports, PS with Aloe vera film exhibit higher hydrophobic with antibacterial activity compared to PS with Acalypha indica film. In addition, the PS/ Aloe vera coated cotton maintained their repellent properties against various liquids for 10 h, while PS/ Acalypha indica coated cotton exhibit anti-wetting property for 4 h. These findings open up new avenues for the preparation of hydrophobic film for various biomedical applications.

Mechanical Equilibrium Dynamics Controlling Wetting State Transition at Low-Temperature Superhydrophobic Array-Microstructure Surfaces

Superhydrophobic materials are significant for engineering applications in the anti-icing field because of their non-wetting property. The interface physical mechanisms of non-wetting properties are important to promote real applications of superhydrophobic surfaces, especially under low-temperature conditions. Here, we found that low temperature could induce the wetting state transition from a Cassie–Baxter state to a Wenzel state. This transition occurred at 14 °C (and 2 °C) on superhydrophobic surfaces with pillar heights of 250 μm (and 300 μm). As a consequence, the driving-force of the Cassie-Wenzel (C-W) wetting transition was induced by the contraction of air pockets on cooling, and the pressure of air pockets supporting the droplet decreased with the contraction degree. Decreasing the pressure of air pockets broke the mechanical equilibrium at the solid–liquid contact interface, and the continuous contraction overcame the resistance in the C-W wetting transition. Based on the analysis of work against resistance in the C-W wetting transition, lower C-W wetting transition temperature was mainly attributed to a higher pillar, which produced more work against resistance to require more energy. This energy was directly reflected by the energy required for continuous contraction of air pockets. Superhydrophobic surfaces with higher pillar structure remain stable non-wetting property at low-temperature conditions. This work provides theoretical support for the application of superhydrophobic materials in low-temperature environments.

High energy surface as a receptor in electrospinning: A good switch for hydrophobicity to hydrophilicity

The lotus leaf surface is modified by covering nanofibers to check its wetting property. The well-known lotus effect of the modified surface is greatly weakened, and a hydrophilic property is found. The geometric potential theory is used to explain the phenomenon, it shows that the two adjacent nanofibers can produce a high geometric potential to push water molecules to move along the fibers, as a result, a hydrophilic surface is predicted after surface modification. An experiment is designed to elucidate the main factors affecting the wetting property of the modified surface of lotus leaf.

Friedel-Crafts alkylation modification and hydrophilic soft finishing of meta aramid

Based on the Friedel-Crafts alkylation reaction, epichlorohydrin is applied to decorate the meta aramid to enhance the comfort of the fabrics. It is obviously more perfect that the samples are treated with the hydrophilic soft finishing agent. In this paper, the effects of modification and finishing time on the structure and properties of meta aramid are studied. The results indicate that the surface roughness, polarity, active point, and wetting property of the modified fabrics are increased, and the loading rate and fastness of the finishing agent on the meta aramid are enhanced. After finishing, the wetting time and the time of water transfer from the surface to the bottom become shorter in the fabrics, and the water absorption rate becomes faster, the core absorption height rises by 60%, the bending stiffness lowers by 39%, the moisture permeability increases by 5.9%, the permeability decreases by 3.6%, and the friction electric voltage reduces by 78%, The longitudinal and weft secondary combustion time increase by 0.3 s and 0.2 s, the smoldering time increase by 0.3 s, and the improving rate of damage length are 5.4% and 7.6%, respectively.

Microstructure and mechanical properties of brazing joint of silver-based composite filler metal

In this article, environmental friendly BAg25Cu40Zn34Sn (BAg-25) and BAg30Cu37Zn32Sn (BAg-30) flux-core solder metal capable of facilitating automatic production of brazing manufacturing processes were prepared. The butt and lap induction brazing tests were carried out on the substrate with BAg-25 and BAg-30. Wettability, microstructure and mechanical properties of the solders on the base metal were studied by field emission scanning electron microscope (SEM-EDS), electron backscattering diffraction (EBSD), tensile testing machine and microhardness tester. Results indicated that the wetting property of BAg-30 with 30% silver content was better than that of BAg-25 with 25% silver content. At the same time, besides copper and silver-based solid solutions, the brazed joint of BAg-30 solder also contain Cu + Ag eutectic phase. In the brazed joint of BAg-25 solder, the grain size is smaller, which makes the tensile strength and the shear strength of the joints better. Therefore, the BAg-25 flux-core solder metal will further reduce the industrial cost and meet the requirements of mechanical properties.

Preparation of Lignite Dust Suppressant by Compound Surfactants and Effect of Inorganic Salt on Dust Suppressant

In order to improve the safety, operability, and cleanability of the dust suppressant, this paper uses the surfactant monomers selected in the previous experiment as the main material formula and adds the inorganic salt as the synergist to prepare the dust suppressant for the PMX. The wetting property of the solution was characterized by the surface tension and contact angle of the pressed coal pieces. The sedimentation experiment was used to screen the compounding system of the surfactant. Finally, the dust suppressant was used to reduce the dust of the PMX in the coal dust simulation system. The results show that (1) the surfactant compounding system can effectively improve the wetting property and the sedimentation time of coal dust. The fast penetration T (0.06%), SDBS (0.15%), and APG (0.20%) are the preferred main ingredients. (2) Adding inorganic salts on the basis of compounding, according to the effect of inorganic salts on the effect of dust suppressant, it is concluded that NaCl (1.00%) is the best synergist. (3) In order to save costs, reduce the amount of surfactant. According to the simulated dust reduction experiment, formula N: anionic surfactant SDBS (0.06%), anionic surfactant fast-permeability T (0.06%), and inorganic salt NaCl (1.00%) are the best for PMX dust fall.