| With development of aerospace and automobile industry, great demands are brought forth in these years on engines of planes or cars, in which oils, as"blood"in engines, play crucial and important roles in operational life span and service efficiency of engines. Water in the oils is one of the main factors, which can accelerate deterioration of oils. Therefore, controlling water content in oils can ensure the safe working of the airplane and automobile.Among all of oil/water separating technologies for engines, coalescence separating technology has been widely used in virtue of its large processing capacity and low energy comsuption and low cost. For an instance, the filter layer is most important part in coalescing separator, which is usually composed of special hydrophobic and oleophilic materials. By using difference of contact properties of the filter layer between water and oil, the water in oil can be effectively held back and remaining oil can passed throughthe filter. So consequently, coalescing separator can separate the water from oil successfully.Hitherto, filter layer of coalescing separator is mostly prepared by spraying imported Teflon (polyfluortetraethylene) onto the metal mesh. However, Teflon can not dissolve in common organic solvents, and have to require high temperature to melt the polymer to form film on the metal mesh. Besides, the film made by Teflon is very thick and its oleophilic property is also not well, which finally cause to increase the flow resistance of the oil and lower the oil/water separating efficiency. Therefore, developing solvent-base fluorinated acrylate (FA) resin to make superhydrophobic and superoleophilic film is very meaningful to increase the precision and efficiency of oil/water separating. Based on these, we focused on studies of fluorinated acrylate film on stainless steel mesh as follows:First of all, fluorinated acrylate copolymers were synthesized by free radical polymerization in solvent. The effects of soft/hard monomers weight ratio, kinds of hydroxylic monomers and their dosages, fluorinated monomer dosage, reaction temperature and fluorinated monomer addition method on the molecular weight of the copolymer, resin viscosity and hardness, adhesion, solvent resistance, etc. of the curing film were investigated. Optical Contact Angle Meter (OCA) measured water contact angles (WCA) of the film prepared by different dosages and adding methods of fluorinated monomer on the stainless steel plate. The effects of concentration of the coating solution and pore size of the mesh on the WCA on stainless steel mesh were also studied. The results reveal that copolymer with low molecular weight, low viscosity and curing film with well adhesion, solvent resistance, oil resistivity and high (low) temperature resistance can be obtained by adjusting copolymer component and optimizing polymerization technique.Addition of fluorinated monomer can increase WCA of the coating obviously, however, when the dosage of fluorinated monomer was larger than 16%, the WCA didn't change any more. Adding the fluorinated monomer one shot at the late reaction stage can take full advantage of it, for less fluorinated monomer was needed to reach the same hydrophobic property. The WCAs on stainless steel mesh were larger than the plate using the same copolymer. When the concentration of the coating solution was 5%, fluorinated monomer dosage was 3%, the WCA on 300 mesh of stainless steel mesh was more than 130°.Secondly, the influence of copolymer composition, length of fluorine-carbon chain and aliphatic chain of higher alkyl (meth) acrylate and addition method of fluorinated monomer on the oil, water contact angles and water rolling property of the coating was discussed when importing higher alkyl (meth) acrylate as oleophilic monomer. The copolymer chemical structure, crystallization, and surface elemental content were analyzed via Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), X-ray Diffraction (XRD), X-Ray Photoelectron Spectroscopy (XPS) etc. The results suggest that the crystalline structure can be obtained at longer fluorine-carbon chain and aliphatic chain, and it is determined by the copolymer composition: when the content of the fluorinated monomer is low, the copolymer is mainly crystallized with side chains of alkyl chains; when the content of the fluorinated monomer is high, the copolymer is mainly crystallized with side chains of fluorinated chains. At low content of the fluorinated monomer, the water rolling property of the coating can be enhanced as increasing the length of aliphatic chains.In addition, the longer the aliphatic chains are, the more oleophilic the coating is. When the side chains are rigid, taking SMA for example, the oleophilicity of the coating can be further enhanced. The wettability of the thermoset resin is more stable than the thermoplastic resin, and the thermoset resin takes less fluorinated monomer than the latter at the same hydrophobic property. It is prone to obtain perfluorinated-end capped copolymer when adding the fluorinated monomer at the later reaction stage, of which the surface free energy is the lowest and water, oil contact angles and water rolling distance reach their maximums.When the length of fluorine-carbon chain n is larger than 6 (n>6) and fluorinated chains are crystalline, the fluorinated chains screen the polar groups and alkyl groups very well, which make the coating excellent hydrophobic and oleophobic property; When n>6 and fluorinated chains are not crystalline, the effect of screening is limited, and the polar groups will be reorganized and migrated after they contact with polar molecules such as water. Hence, the water, oil contact angles and water rolling distance of the coating decrease. When n<6, the fluorinated chains can't screen the polar groups and alkyl groups, as a result, the surface free energy of the coating becomes higher and the the oleophilicity is strengthened by the surface alkyl groups, however, the hydrophobicity of the coating is weakened at the same time.Thirdly, a superhydrophobic and superoleophilic silica film on stainless steel mesh was obtained by simple sol-gel method using tetraethoxysilane (TEOS) and methyl triethoxysilane (MTES) as precursors. The effects of surface morphology and chemical composition on the wetting behavior of the film were discussed and studied by Transmission Electron Microscope (TEM), Field-emission Scanning Electron Microscopy (FSEM), Atomic Force Microscopy (AFM), FTIR, Elementary Analyzer (EA) and XPS. The results demonstrate that when increasing the silica particle size, molar ration of MTES/TEOS, molar concentration of TEOS and aging period, the hydrophobicity of the silica film is enhanced due to the increase of surface roughness or coverage of the methyl groups, but the stability of the silica sol deteriorates for more and more particles agglomerate. So it is rational to prepare the superhydrophobic/superoleophilic film in medium conditions. Diiodomethane droplet, which has higher surface tension, can spread out on the silica film for the capillary force and intrinsic oleophilicity of the methyl groups.Fourthly, the wettability of the silica film can be switched from superhydrophobicity /superoleophilicity to superamphiphilicity by adequate annealing, and then can become ultra-amphiphobicity after surface modification with fluoroalkylsilane monolayer. The analysis of surface morphology and chemistry reveals that the methyl groups are migrated from the surface of silica film at high temperature. Besides, the crystal structure of the silica particles has been changed. The silica film exhibits superamphiphilicity because of the disappearance of the methyl groups. After modified with fluoroalkylsilane, the superamphiphilic film shows ultra-amphiphobicity. There are two reasons, one is the introduction of low surface free energy groups, another is loss of the micro-nano binary structure, which make the wetting regime transfer from Cassie state to Cassie-Wenzel state. Therefore, the water tilt angle increases obviously. The equation of water contact angle in Oil-Water-Solid interface was deduced by Young's equation. The conditions for oil/water separating were obtained and different oil/water separating state for superhydrophobic /superoeophilic, superamphiphilic and ultra-amphiphobic film were rationally explained by the deduced equation.Finally, SiO2/polyacryalte composite coating were prepared by directly blending inorganic nano-silica particles into fluorinated acrylate copolymers and further curing with HDI-trimer. The effects of silica dosage, concentration of coating solution and copolymer composition on the wettability of composite coating were studied. The results suggest that the silica dosage, concentration of coating solution have important influence on the roughness of the composite coating. When the surface free energy of fluorinated copolymer is low, the oil and water contact angles will both increase when increasing the surface roughness. However, when the surface free energy of fluorinated copolymer is little higher, the water contact angle will increase but oil contact angle decrease. The mechanism for oil/water separating is discussed on the stainless steel mesh, and the application in oil/water separating of the composite coating was conducted. The results show that enhancement of the hydrophobicity is the most important for oil/water separating. Taking composite coating using copolymer MMA/SMA/HEMA/FMA for example,in which FMA was added in the earlier stage of the reaction, the oil/water separating efficiency was more than 99% when separating water from n-hexane, petrol, diesel oil, aviation kerosene and hydraulic oil on stainless steel mesh with pore size smaller than 300μm.
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