Effects of pigmentation on siloxane–polyurethane coatings and their performance as fouling-release marine coatings

Siloxane–polyurethane paints were formulated and characterized for coating properties and performance as fouling-release (FR) marine coatings. Paints were formulated at 20 and 30 pigment volume concentrations with titanium dioxide, and aminopropyl-terminated poly(dimethylsiloxane) (APT-PDMS) loadings were varied from 0 to 30% based on binder mass. The coatings were characterized for water contact angle, surface energy (SE), gloss, and pseudobarnacle (PB) adhesion. The assessment of the FR performance compared with polyurethane (PU) and silicone standards through the use of laboratory biological assays was also performed. Biofilm retention and adhesion were conducted with the marine bacterium Cellulophaga lytica, and the microalgae diatom Navicula incerta. Live adult barnacle reattachment using Amphibalanus amphitrite was also performed. The pigmented coatings were found to have properties and FR performance similar to those prepared without pigment. However, a higher loading of PDMS was required, in some cases, to obtain the same properties as coatings prepared without pigment. These coatings rely on a self-stratification mechanism to bring the PDMS to the coating surface. The slight reduction in water contact angle (WCA) and increase in pseudobarnacle release force with pigmentation suggests that pigmentation slowed or interfered with the self-stratification mechanism. However, increasing the PDMS loading is an apparent method for overcoming this issue, allowing for coatings having similar properties as those of clear coatings and FR performance similar to those of silicone standard coatings.     

高寒列车转向架防冰涂料的研究

在高寒地区运行的列车转向架部位容易发生结冰现象，这在一定程度上对行车安全造成隐患。对于平滑表面而言，表面的接触角滞后与冰粘附强度呈现线性关系，即接触角滞后越小，冰粘附强度越低。基于这一基础理论，本文意在构建低滞后的光滑涂层，实现涂层的低冰粘附强度，从而达到易除冰的效果。研究选用 HDI三聚体型多异氰酸酯为固化剂，对比了 3种商品化具有低表面能特性的含氟羟基树脂应用于双组分防冰涂料的性能差异，并采用疏水性最强、防冰性能最优的氟硅树脂制备了综合性能优异的高寒列车转向架防冰涂料。     

激光和等离子处理对复合材料表面涂层附着力的影响研究

为了提高环氧涂料在纤维增强聚丙烯复合材料上的附着力,采用激光和等离子体表面前处理方法,应用超景深显微镜、粗糙度测定仪、接触角测试仪以及附着力测试仪,研究了激光和等离子体表面处理对纤维增强聚丙烯复合材料表面形貌、表面粗糙度和表面水接触角的影响,并且探究了这 2种表面处理方式对环氧涂层在复合材料上附着力的影响。结果表明： 2种处理方式均可明显提高环氧涂层在基材上的附着力,附着力均可由不到 1 MPa提高至 8 MPa以上。     

Surface and mechanical properties of an organic-inorganic super- hydrophobic coating using modified nano-SiO2 and mixing polyurethane emulsion as raw materials

A series of organic-inorganic super-hydrophobic coatings were prepared using nano-SiO₂ particles modified by fluorine and silicone coupling agents, and a mixing polyurethane emulsion as main raw materials. The mixing polyurethane emulsion was consisted of the polyurethane emulsion end-terminated by double bond (WPUD) and polyurethane emulsion modified by silicone (WPUS). The influence of content of modified nano-SiO₂ particles and the weight ratio of WPUS to WPUD on microstructure and hydrophobicity of the coating surface were studied. The morphologies of coating surface were examined using SEM and AFM, hydrophobicity of the coating was researched by examining static water contact angle and so on. It was found that modified nano-SiO₂ particle was an indispensable factor during the preparation of super-hydrophobic coating. The roughness and hydrophobicity of the coating surface were enhanced obviously with an increase of the content of the modified nano-SiO₂ particles. When the content of the modified nano-SiO₂ particles increased up to 1.5%, the surface of coating possessed good super-hydrophobicity, and static water contact angle reached 169.1°. It was also noticed that the weight ratio of WPUS to WPUD in the base layer has also an important influence on the hydrophobicity and mechanical property of coating surface. With an increase of the ratio of WPUS to WPUD the hydrophobicity of the coating was enhanced, the tensile strength and peel strength reduced, but the elongation at break increased. When the weight ratio of WPUS to WPUD reaches up to 9/100, the static water contact angle reaches the maximum value of 169.1°.     

Improvement of anti‐icing properties of low surface energy coatings by introducing phase‐change microcapsules

Polymers with low surface energy such as silicone and fluoropolymers are widely applied in preparing anti‐icing coatings, but they may have some limitations. To improve the anti‐icing properties of the coatings, composite coatings were developed by introducing phase‐change microcapsules (PCMs). Room temperature vulcanized silicone rubber and a fluorosilicone methacrylate copolymer were examined. Tests involving infrared thermal imaging, icing delay time, and ice shear strength were performed to determine the anti‐icing properties of the coatings. It was found that during cooling the composite coatings containing PCMs could release the latent heat of phase change to delay the icing process of water droplets on its surface. The introduction of PCMs increased the surface roughness, and the ice shear strengths of the composite coatings could remain at a low level and ice on the coatings could be easily removed, indicating that PCMs could be practicably applied in anti‐icing coatings. POLYM. ENG. SCI., 58:973–979, 2018. © 2017 Society of Plastics Engineers     

A robust quasi-superhydrophobic ceria coating prepared using air-plasma spraying

Hydrophobic coatings that could survive in harsh environment have a wide range of applications from industry to houseware. However, the state-of-the-art polymer-based coatings cannot meet such requirements due to their low melting point and poor wear resistance. In this study, we reported a plasma sprayed ceramic coating made of ceria with exceptional hydrophobicity, high-temperature stability, and good wear resistance. The coating exhibited a water contact angle (WCA) up to 139°, due to the intrinsic hydrophobicity of ceria and unique surface morphology produced by plasma spraying. The WCA only slightly decreased to 131° after annealing at 773 K. In addition, the polished coating (WCA ~ 116°) was still more hydrophobic than the sintered bulk specimen (WCA ~ 95°) with the same composition and roughness, which can be attributed to the surface chemistry change induced by Ar⁺ ion bombing by plasma. It is believed that such robust hydrophobic coating should have great potential in engineering application.     

水性环氧树脂/纳米SiO2复合疏水涂层的制备及性能研究

用氨基硅油（ APDMS）改性水性环氧树脂（ EP）得到疏水性的环氧树脂乳液（ APDMS-EP）;用 1H,1H,2H,2H-全氟辛基三乙氧基硅烷（ FAS）与纳米 SiO₂反应得到氟改性纳米 SiO₂（F-SiO₂）。采用不同比例的 F-SiO₂与 APDMS-EP进行复配,室温固化制备疏水涂层,并对 F-SiO₂的结构进行了表征,研究了 F-SiO₂用量对涂层的接触角、铅笔硬度、附着力、热稳定性及耐腐蚀性能的影响。结果表明： APDMS的引入使水性环氧树脂涂层的水接触角从 47.3°提高到 97.7°;加入 F-SiO₂后涂层疏水性进一步提高,当加入 15%的 F-SiO₂时,涂层对水和丙三醇的接触角分别为 120.3°和 104.5°,F-SiO₂的加入也增强了涂层的防腐性能。     

污损释放型涂料的防污与减阻性能研究

制备了一种以有机硅树脂为基体树脂的污损释放型涂料,并对其防污性能与减阻性能进行了研究。结果发现,硅油能够渗出到涂层的表面,引起表面形貌和表面能的强烈变化。随着硅油渗出量的增加,涂层表现出的"结构表面能"越大,并有利于防污性能的增强。污损释放型涂层的表面粗糙度远小于通用自抛光型涂层的表面粗糙度,并且在不同雷诺数下均表现出了良好的减阻效果。所研制的污损释放型涂料同时具有良好的防污性能与减阻性能,能够为我国商品化环境友好型防污减阻涂料的研发提供借鉴。     

Transparent polysilicone coatings as protecting films for gold commemorative coins

Novel transparent organic silicone resin coatings were successfully prepared through the reaction between the alkoxy groups of methyltrimethoxy‐silane (MTMS) and γ‐aminopropyltriethoxysilane (APTES) and hydroxyl groups of hydroxyl terminated silicone oil (HTSO). The influences of different monomer feed mass ratio on the coating properties were investigated via measuring the hydrophobicity and hardness of coating films. The coating films were characterized with IR, UV, TG, scanning electron microscope (SEM), and automatic contact angle meter. Some properties of coating films, such as adhesion, impact resistance, and wear‐resistance, were also evaluated. The results indicated that these coating films formed on the surfaces of gold commemorative coins possessed some good properties including high hydrophobicity, high water contact angles, high light transmittance, good heat‐resistance, adhesion, hardness, and weatherability, etc. Moreover, the uniform, clear, transparent, and dense coating films did not cover the symphony surface patterns or affect the metallic luster. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

含硫极压抗磨剂对苯基硅油摩擦学性能的影响

将硫化烯烃添加到苯基硅油中,采用四球试验机考察了硫化烯烃对苯基硅油摩擦学性能的影响。结果表明,添加硫化烯烃可降低苯基硅油的磨斑直径和摩擦系数;当苯基硅油中国产硫化烯烃或进口硫化烯烃的质量分数为5%时,其烧结负荷较纯苯基硅油分别提高了118.75%和181.25%,且后者比前者高28.57%;但两种硫化烯烃都不能改善苯基硅油的油膜强度。     

Preparation and characterization of a greenish yellow lackluster coating with low infrared emissivity based on Prussian blue modified aluminum

Greenish yellow lackluster coatings with low infrared emissivity were prepared by Prussian blue (PB) surface modified Al powders and polyurethanes. The morphology and component of PB/Al powder were characterized by scanning electron microscopy and X-ray diffractometer. The infrared emissivity, surface gloss and visible light color of PB/Al composite coating were investigated by an infrared emissometer, a glossmeter and a colorimeter, respectively. Mechanical properties of PB/Al composite coatings were studied by using adhesion test and impact strength test. The results indicate that PB/Al powder decreases not only the gloss of the coating, but also its emissivity within the wavelength range of 8–14 μm. The composite coatings have good adherence and impact strength at PB/Al content below 50 wt.%, and then the mechanical properties decrease in the PB/Al content range from 50 wt.% to 60 wt.%. By comparing PB/Al composite coating and Al powder tinting coating with the same color and surface gloss, PB/Al composite coating exhibits significant lower infrared emissivity, which is attributed to closer inter-powder distances of metallic fillers and higher electrical conductivity in the coating.     

Role of Sn on the adhesion in Cu–Sn alloy-coated steel–rubber interface

Cu–Sn coatings with varying Sn content were deposited on steel substrate by immersion route and the effect of variation of Sn content and the substrate roughness on the interfacial adhesion strength of Cu–Sn-coated steel substrates vulcanized with styrene butadiene rubber were investigated. The surface roughness of the coatings did not vary compared to pristine steel substrate with change in Sn weight% in the coatings. The coated surfaces exhibited bare spots or deep trough as micro-discontinuities in the coatings, where formation of Fe₂O₃ was evident from SEM-EDS, AES, and XPS analysis. Microstructural study of the coating cross-section and coating-substrate interface by transmission electron microscopy of cross-sectioned samples revealed inadequate penetration of coating inside these troughs. Peel test carried out on the Cu–Sn-coated steel–rubber joints showed mixed mode i.e. adhesive and cohesive mode of interfacial fracture irrespective of the coating composition. The peel test further indicated higher interfacial adhesion strength for Cu–Sn-coated samples than pure Cu-coated samples, with an optimum adhesion strength for the coatings containing 3–4?wt.% Sn.     

Facile fabrication of superhydrophobic polysiloxane/magnetite nanocomposite coatings with electromagnetic shielding property

Superhydrophobic coatings, with a water contact angle (WCA) of 158.3° and a sliding angle of 4.3°, were readily prepared by mixing silicone resin, aminopropyltriethoxysilane and Fe₃O₄ nanoparticles, and subsequently curing at an ambient temperature. The surface wettability, surface morphology and composition, and long-term durability of the coatings were investigated by WCA analysis, field emission scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, and QUV accelerated weathering tests, respectively. The results show that the coatings display a pencil hardness of B, excellent weatherability, and electromagnetic shielding effectiveness beyond 60% in the frequency range of 10–3000 MHz.     

Skin-customized wearable device adhesive without skin damage

Wearable medical devices are gaining popularity owing to their potential for seamless integration with the human body and long-term monitoring of physiological activity. However, conventional adhesives were developed based on the assumption of healthy adult skin and may not account for variations in skin characteristics across different species, environments, and body parts. Consequently, the adhesive strength of wearable devices may significantly differ depending on the skin surface to which they are attached, potentially causing skin damage. In this study, we developed a customized wearable-device adhesive without skin damage by analyzing the characteristics of the skin surface based on oil and water content and roughness according to different species and parts. Our findings demonstrated that increased root-mean-square roughness of the skin surface led to reduced contact area and decreased adhesion force between the polydimethylsiloxane (PDMS) pad and skin surface. Surprisingly, hairless skin exhibited 1.5 times higher adhesion strength than hairy skin due to stronger molecular forces resulting from the higher surface energy of the skin. Additionally, the hole-patterned PDMS pad on sweaty skin displayed improved adhesion properties compared to the cylinder-patterned PDMS pad. Therefore, customized wearable adhesives provide an effective strategy for developing skin-damage-free wearable devices.     

Development of polyorganosilazane–silicone marine coatings

The objective of the present work is the development and characterization of marine coatings based on polyorganosilazanes (PSZ). Two types of coatings containing silicone oils and biocidal compounds were investigated as anticorrosive and antifouling coatings. The flexibility, hydrophobicity and adhesion properties of the PSZ-based coatings on aluminum substrates were studied. Static immersions in natural seawater were investigated to evaluate the antifouling performances of these coatings. The corrosion properties were studied by salt spray tests. Results demonstrated that coatings based on silicone oils appeared to be the most efficient coatings in terms of antifouling and anticorrosive properties. Ten-month antifouling efficiency was revealed for biocide-free polydimethylsiloxane-based PSZ coatings in natural seawater static immersion. The adjunction of dicopper oxide as biocidal pigments was shown to decrease the stability in cans of the corresponding paints and therefore decreasing the flexibility of coatings. In addition, this pigment affected badly the anticorrosive properties of the coatings together with a short antifouling efficiency time. Thus, the silicone oil-based PSZ displayed remarkable advantages in addition to their dual antifouling and anticorrosive properties which are the absence of biocidal compounds released in marine environment and the absence of volatile solvent.     

Fractal analysis of surfaces roughened by grit blasting

Surfaces roughened by grit blasting influence the adhesion strength of plasma-sprayed ceramic coatings. The average surface roughness has been used to evaluate the surface topography of such surfaces. It is well known that the adhesion strength of ceramic coatings reaches a maximum value at a certain substrate surface roughness. However, this result cannot be understood based on only surface roughness. The blasted surface has fractal characteristics. There are two types of fractal surfaces, which are characterized by self-similarity and self-affinity. Using fractal analysis to evaluate the surface topography of substrates, the fractal dimension was measured for the roughened surfaces. The maximum fractal dimension was attained at a blasting angle of 75°, where the adhesion strength also reached approximately its maximum value. It is concluded that the fractal dimension is a more appropriate measure than the average surface roughness for evaluation of the adhesion strength of ceramic coatings.     

The effect of plasma‐polymerised silicon hydride‐rich polyhydrogenmethylsiloxane on the adhesion of silicone elastomers

BACKGROUND: Silicone elastomers have outstanding material properties including good thermal stability, low electrical conductivity, biocompatibility and resilient physical and chemical properties. These elastomers, however, exhibit relatively poor adhesion to stainless steel, and the use of a nanometre thick plasma‐polymerised primer layer as a means of enhancing this adhesion was investigated in this study. The primer coatings studied consisted of polyhydrogenmethylsiloxane (PHMS), tetraethyl orthosilicate (TEOS) and mixtures of these two liquid precursors. RESULTS: The plasma‐polymerised primer coatings were deposited onto stainless steel substrates using a PlasmaStream^? atmospheric pressure plasma jet system. Deposited coatings were examined using ellipsometry, contact angle measurements, optical profilometry, Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopy and scanning electron microscopy. The adhesion of silicone elastomers bonded to the primed and bare stainless steel surfaces was assessed using 45° adhesion strength measurements. Elastomer adhesion was correlated with surface energy, thickness and roughness. CONCLUSION: An up to 15‐fold increase in adhesive fracture energy was observed for silicone elastomers bonded to the primed versus untreated stainless steel. The highest adhesion was observed for a coating deposited from a PHMS‐to‐TEOS precursor molar ratio of 3 to 1. Copyright © 2009 Society of Chemical Industry     

Water- and ice-repellent coatings

Conclusion  The study on water-repellent coatings and their effect on adhesion of ice is summarized as follows:

Comparison of drag characteristics of self-polishing co-polymers and silicone foul release coatings: A study of wettability and surface roughness

An experimental study has been carried out to evaluate the drag characteristics of different self-polishing co-polymers (SPC) (tin based and tin-free) and a silicone foul release (FR) coating. Drag measurements have been performed on a smooth aluminum cylinder connected to a rotor device. Various coatings on cylinders were examined and differential length technique was also used to avoid the end effects during rotation. Surface energy of the coated samples was determined using static contact angle measurement. Characteristic roughness measurements of the coated surfaces were evaluated with atomic force microscopy (AFM) technique.

Drag measurements showed that the frictional resistance of the FR coated cylinders was lower than that of SPC coated samples.

Contact angle results showed that the critical surface tension and its polar component for silicone FR coating are less than SPC coatings. This prevents firm adhesion of fouling organisms on underwater hulls.

AFM studies revealed a lower surface roughness for silicone FR coating as compared to SPC coatings. Also, its surface texture is considerably different from SPC coatings.

It can be concluded that the drag characteristics of a surface are affected by its free energy and roughness parameters.     

Comparison of drag characteristics of self-polishing co-polymers and silicone foul release coatings: A study of wettability and surface roughness

An experimental study has been carried out to evaluate the drag characteristics of different self-polishing co-polymers (SPC) (tin based and tin-free) and a silicone foul release (FR) coating. Drag measurements have been performed on a smooth aluminum cylinder connected to a rotor device. Various coatings on cylinders were examined and differential length technique was also used to avoid the end effects during rotation. Surface energy of the coated samples was determined using static contact angle measurement. Characteristic roughness measurements of the coated surfaces were evaluated with atomic force microscopy (AFM) technique.Drag measurements showed that the frictional resistance of the FR coated cylinders was lower than that of SPC coated samples.Contact angle results showed that the critical surface tension and its polar component for silicone FR coating are less than SPC coatings. This prevents firm adhesion of fouling organisms on underwater hulls.AFM studies revealed a lower surface roughness for silicone FR coating as compared to SPC coatings. Also, its surface texture is considerably different from SPC coatings.It can be concluded that the drag characteristics of a surface are affected by its free energy and roughness parameters.