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The nanostructured coatings research progress and development trend

Introduction
    With the world attaches great importance to environmental protection, increasing the quality of life and the continuous development of various high-tech industries, the performance requirements of the coating is also rising. Paint products, environmental protection, health, high-performance, multi-functional and intelligent development is an inevitable demand of social development. However, the rapid development of the coatings industry today, the traditional the resin synthesis method or coating formulations designed to further enhance the performance and development of the existing coating new generation of functional coatings space has plastisol coated chain become smaller and smaller. For nearly 10 years, a series of studies at home and abroad, nanomaterials and nanotechnology applications can break through the technical bottleneck of the traditional the resin synthesis method and the coating preparation methods to achieve the traditional coating high performance and new functional coating provides possible. , At home and abroad mainly around the new resin synthesis method, the introduction of nanoparticles and coating the surface of the nano-structure design and construction undertaken the preparation of nanostructured coatings research, and some progress has been made.
    1 using the new resin synthesis method to obtain a new film material
    Resin as the coating of the key materials --- film-forming substances, directly affects the coating of the physical, chemical, mechanical properties and coating surface microscopic structure, etc.. To this end, in recent years, people tried by exploring new resin synthesis method to obtain a new resin film-forming material. For example, the emulsion polymerization is widely used in synthetic resins, coatings, plastics, rubber and adhesive industry. But conventional emulsion generally require use of a large number of small organic molecules emulsifiers form micelles in the water phase first, and then through the initiators dissolved in water and a small amount of monomer, resulting oligomer radical, these free radicals into the emulsifier gum bundle chain growth, chain termination, latex particles through the surface emulsifier molecules electrostatic repulsion and (or) the steric hindrance effect and stability. Small organic molecules emulsifiers eventually remaining in the resin, the properties of the coatings have a significant negative effects (such as stain resistance and weather resistance and poor). For this reason, in recent years, with the auxiliary monomer as the driving force to the acid - alkali new soap-free emulsion polymerization method. For example, Armes [1-3] using nano-SiO2 particles the surface silanols weakly acidic characteristics, adding a small amount of auxiliary monomers containing basic groups in the polymerization of the monomers in the polymerization process, the nano-SiO2 particles by acid - the base interactions adsorbed to the surface of the monomer droplets or polymer latex particles, from emulsifiers effect, the whole process without adding any organic small molecule emulsifier, a soap-free emulsion polymerization method of the acrylic resin. OF [4-6] to the acid - base, electrostatic or hydrogen bonding to the driving force, obtained nano SiO2 particles of the acrylic resin of the "emulsifiers" soap-free emulsion polymerization method. --- One of the world's largest chemical company BASF in Germany [7] this nano-SiO2 particles stable acrylic resin soap-free emulsion for industrial application and found that the coating of stain resistance, water resistance, durability and all There are significantly improved. Schmid et al [8] also relevant film-forming properties of the emulsion system. Author in the study of nano-SiO2 / styrene-acrylic hybrid emulsion film-forming properties, also found that the latex film photonic crystal characteristics [9] can be obtained through this method does not require any pigment colorful structure color coating. Koukiotis [10] prepared by microemulsion polymerization method highly transparent MMA / BA copolymer microemulsion solid content with ordinary polymer emulsion. They found that the prepared emulsion has a very peculiar nature, not only prepared film is excellent, and the minimum film-forming temperature dropped significantly, and has laid a good foundation for the development of the new type of water-based nano resin. In addition, the design and synthesis of nano-polymer is also an important direction of the resin with specific branched structure. It has been reported [11], hyperbranched polymers in the premise of the same relative molecular mass is lower than the linear polymer viscosity, the viscosity of dendrimer totally inconsistent with the existing viscosity - law of relative molecular mass, its viscosity in the nano-scale range unusually reduced, as shown in Figure 1, the novel coating provides a huge potential opportunity for the synthesis of the resin.
    Resin nano technology either in theory or prepared on are a good start, but the new nano resin performance also, in theory, can not effectively predict, but there are also many problems in the preparation has not been effectively addressed, such as in inorganic nanoparticles stable emulsion polymerization aspects, how to achieve control of the polymer particles in the range of nano-scale; microemulsion polymerization how to further improve the solid content and lower emulsifier content; Preparation of nano resin in dendritic how controlled structure and macro preparation requires innovation theory and methods, break through the bottleneck of the design and preparation of nano resin technology to provide theoretical and technical support for the preparation of a new generation of high-performance resin.
    Direct introduction of inorganic nanoparticles in order to improve the properties of the coating
    Inorganic nanoparticles can be generated by blending method, in situ method, introduced into the resin and coating of self-assembly methods. The different nanoparticles gives the different properties of the coating, such as: high hardness and high abrasion resistance to scratching (SiO2, Al2O3, ZrO2, etc.), UV shielding (ZnO, TiO2, CeO2, etc.), antibacterial (Ag, ZnO , TiO2, etc.), electrical conductivity (carbon nanotubes, ATO, etc.), barrier properties (boehmite, clay, etc.) and the like. Zhou et al [12] using nano-SiO2 particles to improve the two-component acrylic polyurethane and polyester polyurethane coating hardness and scratch resistance. Bauer et al [13] nano-SiO2 or Al2O3 particles modified to UV-curable acrylate coatings, scratch resistance coating has been improved significantly. Harreld et al [14] using methacryloxy propyl trimethoxy silane and methyl methacrylate (MMA) copolymer, obtained by polymerization to prepare the ultra-high hardness, low shrinkage transparent hybrid coating. Xiong et al [15] obtained by the hydrolysis of the precursor TiO2 sol and functionalized polyacrylate composite gained high refractive index and high UV shielding transparent organic - inorganic hybrid coatings. Yuwono [16] titanium isopropoxide precursor prepared nanocrystalline TiO2-PMMA nonlinear optical coatings. Yeh et al [17] intercalated clay with surfactant polymer composites with PMMA, poly ethoxyaniline greatly improved of these polymer coating for steel corrosion protection. Kumar et al [18] Lee _______ free radicals generated in the vegetable oil alkyd resin dry film-forming process of auto-oxidation of a reducing agent, benzoic acid silver precursor Ag nano-particles in situ generated anti-bacterial coating, such as Figure 2. The process is simple, and the high value of green commercial applications. , Sangermano [19] of the rare earth ion doped LaF3 nanoparticles with epoxy coating composite prepared nano-structured coatings for laser waveguides directly written to the field.
    Research in this area is relatively large, but because the resin and the coating system is very complex, the system either is aqueous, and may be solvent-based, but also can be solvent-free (powder coating, UV-curing); resin molecular chain can be either polarity can also be non-polar. In particular, because of environmental pressures, resin and paint water-based coatings industry trends, the introduction of inorganic nanoparticles is necessary to consider its dispersion stability in aqueous systems, but also pay attention to the film curing resin interaction of the coating of the molecular chain. Therefore, the need to explore inorganic nanoparticles for different resin paint coating system to import the new method, the establishment of the inorganic nanoparticles in different resin paints and coatings in the universal dispersion stability control methods, the development of the surface of inorganic nanoparticles design, stable dispersion theory.
    3. Surface micro-and nano-structures constructed to obtain the functional coating
    Use of a polymer chain segment and the difference in solubility in a solvent having a special structure of the surface can be obtained. For example, Erbil et al [20] of the polypropylene (PP) was dissolved in xylene / methyl ethyl ketone mixed solvent, since the p-xylene is a good solvent for PP, butanone nonsolvent PP segment in a solvent in the uneven distribution. This solution was coated on a glass plate, placed in the solvent was removed under vacuum and can be prepared by a porous structure of the PP film, the surface water contact angle of up to 155 °. Similarly, the difference of the different segment of the block polymer in the same solvent can also be obtained in the super-hydrophobic surface. Xie et al [21] using a triblock copolymer of PMMA-PP-PMMA segments formed by the difference in solubility in the solvent dimethylformamide (DMF) in the micelle core polypropylene segment, this structure similar to the papillae of the lotus leaf surface, the same having a secondary structure, after evaporation of DMF, the micelle structure can be well deposited on the surface, to form a super-hydrophobic surface, and the contact angle with water of up to 160 °. Yabu, etc. [22] will be PMMA-poly methacrylic perfluorooctanoate ester-PMMA triblock copolymer was dissolved in the AK-2559 of solvent (CF3CF3CHCl2/CClF2CHClF mixed solvent), the solution after coating is placed a humidity of 40% ~ 60% humid air environment, the occurrence of self-assembly behavior honeycomb structure, the honeycomb structure has been formed after the release treatment orderly pin cushion structure, an alkoxysilane group) formamidinyl propylamino] -6 - methyl - 4 - hydrogen pyridone, the substance in ethyl acetate via hydrogen bonds may be formed on both ends of the three oxide group-rod-shaped dimer molecules nest formed by the hydrolysis of Si-O-Si bond crosslinked structure by low surface energy material modified after the formation of the super-hydrophobic surface. Zhao et al [24] Preparation of polystyrene - polydimethyl siloxane (PDMS) block copolymer micelle solution by a gas-induced phase separation method of the PDMS chain segments in the surface enrichment, to thereby obtain a super-hydrophobic sexual characteristics. Sun et al [25] such as the poly-isopropyl acrylamide as a low surface modified rough surface of the material when the temperature from 25 ℃ to 40 ℃, the the original intramolecular hydrogen bonds into intermolecular hydrogen bonds, the polymer chain segment distorted rearrangement, hydrophobic segment tends to surface, the flat surface of the contact angle changed from 63.5 ° to 93.2 °, while the rough surface of the contact angle changes from 0 ° to 149.3 °.
    Recently, Professor Washington University Wooley et al [26] and the University of North Dakota Webster Professor [27] in the financial support of the U.S. Navy Department, were synthesized hyperbranched fluoropolymer - polyethylene glycol reticular resin and PDMS - polyurethane block-copolymer resin, the dry film of the resin, phase separation occurs, and the surface to form nano-scale unevenness of morphology. Preliminary studies indicate that this coating has excellent resistance to serum proteins, hemagglutinin and lipopolysaccharide adhesion properties.
    Other structures with micro-and nano-structural morphology of the surface of the method include: lithography, laser etching, deposition or chemical deposition method, hydrothermal method, sol - gel method, carbon nanotubes law electrospinning method, template method . But these methods are difficult to apply resin coating micro-and nano-structure to build on. Required under harsh conditions, the equipment is expensive Currently, the most likely still on the formation of micro-polymer phase separation method or a self-assembly method, but so far only for the preparation of the coating of the small area, and when the temperature of the surface of the micro structure obtained is melted and morphology to be easily destroyed, satisfied that the structure and morphology of the polymer composition and structure, and the formation conditions of very high special requirements of the solvent used in the paint industry to prohibit the use of comprehensive performance of the polymer used, it is difficult as the deposition of the coating substances. Therefore, you need to have practical value of the polymer film-forming resin, to investigate the the corresponding coating system micro-nanostructure coating method, in particular, need to develop a macro coated surface and bulk nanostructures possess controllable preparation method provide theoretical guidance for the development of a new generation of functional coatings.
    4 Conclusion
    Overall, the application of nanomaterials and nanotechnology in the coatings industry is still in the initial research stage, basic research at home and abroad at the same level. Nanomaterials and nanotechnology in order to truly achieve large-scale application in the resin coating must also address the following key scientific and technical issues: (1) has a nano-scale and the effect of the new resin design synthesis and film formation mechanism, development structure and controlled performance of high-grade resin synthesis methods, design synthesis of novel resin film-forming material; (2) understand and summarize inorganic nano particles surface design and its general laws in different resin dispersion paint coating system stability, its uniform and stable dispersion of universal control method; (3) reveal nanostructured coatings law and principles of design and their microstructure and performance, clarify the formation mechanism of the development of nano-structured coating has practical value macro amount of preparation technology, especially with bulk nanostructured coatings macro preparation techniques; (4) reveals the evolution of the micro-structure and properties of micro-structure and properties of nanostructured coatings and their conditions of service, the establishment of the nano-structured coating layer performance evaluation method and the stable control method. We are confident that the nanostructured coatings will become the cornerstone of the future and even the recent scientific and technological development of the coatings industry, and make an important contribution to the development of new materials.

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