Structures and antifouling properties of low surface energy non-toxic antifouling coatings modified by nano-SiO<Subscript>2</Subscript> powder

Antifouling coatings are used to improve the speed and energy efficiency of ships by preventing organisms, such as barnacles and weed, building up on the underwater hull and helping the ships movement through the water. Typically, marine coatings are tributyltin self-polishing copolymer paints containing toxic molecules called biocides. They have been the most successful in combating biofouling on ships, but their widespread use has caused severe pollution in the marine ecosystem. The low surface energy marine coating is an entirely non-toxic alternative, which reduces the adhesion strength of marine organisms, facilitating their hydrodynamic removal at high speeds. In this paper, the novel low surface energy non-toxic marine antifouling coatings were prepared with modified acrylic resin, nano-SiO₂, and other pigments. The effects of nano-SiO₂ on the surface structure and elastic modulus of coating films have been studied, and the seawater test has been carried out in the Dalian Bay. The results showed that micro-nano layered structures on the coating films and the lowest surface energy and elastic modulus could be obtained when an appropriate mass ratio of resin, nano-SiO₂, and other pigments in coatings approached. The seawater exposure test has shown that the lower the surface energy and elastic modulus of coatings are, the less the marine biofouling adheres on the coating films. Supported by High-Tech Research and Development Program of China (Grant No. 2004AA001520)     

海洋污损生物粘附机制及防污涂层表面工程

任何浸入海水的结构物均会受到海洋污损生物的附着。 在物体表面涂覆防污涂料是最广泛的防污方式,无毒污损脱附型防污涂料已成为当前的研究热点。 分析了污损生物的粘附过程及界面粘结作用,探讨了表面能、涂层模量、表面化学成分、微观形貌、颜色等因素对涂层防污效果的影响,并指出涂料工程化中必须解决的问题。     

Dynamical Mechanical Analysis and Curing Analysis of Fouling Release Coatings and Components

A commercially available fouling release (adsorbed foulants removed by shear flow) coating based on poly(dimethylsiloxane) and a commercial marine epoxy primer have been analyzed by diffusing wave spectroscopy and by thermal and dynamical mechanical methods. Diffusing wave spectroscopy reveals 7–9 distinct relaxation intervals over short (minutes) to long (20 hour) time scales. Several junctures of these intervals are shown to correlate with mechanically determined film formation parameters, such as set to touch times, tack free times, and dry through times. Thickness series of coatings made by casting illustrate similarities and distinct differences between the epoxy primer and poly(dimethylsiloxane)-based fouling release coating formulations. Several low temperature β transitions are resolved in the fouling release coatings in addition the α (T_g) transition in both formulations. A scaling analysis of the thickness series data shows that both the primer and the top coat exhibit a negative exponent for thickness; −0.77 for the epoxy; −1.2 for the top coat. Stress-strain experiments reveal further significant difference between these two types of elastomers. The elastic modulus for the epoxy is 1000-fold higher than for the topcoat. A small elastic modulus is thought to be key in the successful functioning of fouling release coatings. Analyses of substrate effects (wire mesh, fiberglass braid) and of coating or loading levels on dynamical mechanical properties, in comparison with thickness series of thin films are presented. The woven braid offers the advantage that it can be loaded more easily than can wire mesh substrates. The negative exponents show that thinner coatings may be more mechanically resilient than thicker coatings, as the ability to store and dissipate mechanical energy decreases as thickness increases.     

水性防污涂料的研究进展

海洋污损生物是海洋资源开发首先要面对的问题。防污涂料是防除海洋污损生物的关键材料。传统的防污涂料虽然发展成熟,但以油性溶剂为介质,存在挥发性有机物(VOC)排放过高、环境污染严重的问题。不释放VOC的水性涂料符合绿色无污染的环保要求,是防污材料领域研究的热点。本文对最重要的四种水性防污涂料(污损释放型水性低表面能防污涂料、自抛光型水性防污涂料、污损阻抗型水凝胶海洋防污涂料、强碱释放型水性硅酸盐防污涂料)从防污机理、制备方法和存在的问题等几个方面进行了综述,并对水性防污涂料的发展趋势进行了展望。     

二氧化硅纳米颗粒/硅树脂复合超疏水功能涂层的制备和性能研究

将二氧化硅纳米颗粒和硅树脂制成混合液,采用喷涂法(spray-coating)制备出了具备超疏水性的复合涂层.研究了二氧化硅、硅树脂不同含量配比对涂层疏水性能的影响,结果表明复合涂层的接触角随二氧化硅含量的增加而增加.在二氧化硅含量大于3%(质量分数)时,涂层显现超疏水性;当二氧化硅含量为3%(质量分数)、硅树脂含量为7%(质量分数)时,涂层与水的接触角达到151.6°,滚动角接近0°.通过扫描电子显微镜(SEM)观察涂层表面的微观结构,发现超疏水性的涂层具备微-纳复合阶层结构,类球状突起粒径在5μm左右,类球状突起上分布纳米团聚颗粒,直径约为50 nm.这种类似荷叶表面的微(纳复合阶层结构,结合硅树脂的低表面能,使得复合涂层具备了超疏水性能.     

LLDPE/纳米SiO_2复合材料的力学性能和光学性能研究

采用熔融共混方法制备了LLDPE 纳米SiO2 复合材料 ,并对该体系的力学性能和光学性能进行了系统研究 .结果表明 ,随着纳米SiO2 的加入 ,复合材料的弹性模量显著提高 ,冲击强度与拉伸强度呈峰形变化 ,且均在SiO2 含量为 3phr左右达到最大值 .加入少量的纳米SiO2 后 ,复合材料薄膜对长波红外线 (7～ 1 1 μm)的吸收能力较LLDPE膜有了显著提高 ,透光率略有下降但雾度提高 ,透光质量得到改善 .同时表明 ,纳米SiO2 的表面处理方法对膜的光学性能有显著影响     

Contact angle hysteresis, adhesion, and marine biofouling

Adhesive and marine biofouling release properties of coatings containing surface-oriented perfluoroalkyl groups were investigated. These coatings were prepared by cross-linking a copolymer of 1H,1H,2H,2H-heptadecafluorodecyl acrylate and acrylic acid with a copolymer of poly(2-isopropenyl-2-oxazoline) and methyl methacrylate at different molar ratios. The relationships between contact angle, contact angle hysteresis, adhesion, and marine biofouling were studied. Adhesion was determined by peel tests using pressure-sensitive adhesives. The chemical nature of the surfaces was studied by using X-ray photoelectron spectroscopy. Resistance to marine biofouling of an optimized coating was studied by immersion in seawater and compared to previous, less optimized coatings. The adhesive release properties of the coatings did not correlate well with the surface energies of the coatings estimated from the static and advancing contact angles nor with the amount of fluorine present on the surface. The adhesive properties of the surfaces, however, show a correlation with water receding contact angles and contact angle hysteresis (or wetting hysteresis) resulting from surface penetration and surface reconstruction. Coatings having the best release properties had both the highest cross-link density and the lowest contact angle hysteresis. An optimized coating exhibited unprecedented resistance to marine biofouling. Water contact angle hysteresis appears to correlate with marine biofouling resistance.     

Elastic modulus profiles in the cross sections of drying alkyd coating films: modelling and experiments

The temporal development of the modulus of elasticity and its profile were studied in water-borne alkyd coatings during the drying process of the coating films. Values of the Young’s moduli of elasticity of free coating films were measured using tensile tests. Since the elastic modulus is related to cross-link density, the values of the moduli give information on the advancement of the drying process. A mathematical model was developed to predict the degree of effective cross-linking and the mechanical behaviour of the drying coating films with different thicknesses. This model is based on trends observed by confocal Raman microspectroscopy, which exhibit the profile of the consumption of double bonds and thus can be used to monitor the development of cross-link density as a function of depth from the film surface. The average values of the Young’s measured moduli were successfully described by the numerical model as a function of drying time.     

Oscillatory shear response of moisture barrier coatings containing clay of different shape factor

Oscillatory shear rheology of barrier coatings based on dispersed styrene-butadiene latex and clay of various shape factors or aspect ratio has been explored. Barrier performance of these coatings when applied to paperboard has been assessed in terms of water vapour transmission rates and the results related to shape factor, dewatering and critical strain. It has been shown that a system based on clay with high shape factor gives a lower critical strain, dewatering and water vapour transmission rate compared with clays of lower shape factor. The dissipated energy, as calculated from an amplitude sweep, indicated no attractive interaction between clay and latex implying a critical strain that appears to be solely dependent on the shape factor at a constant volume fraction. Particle size distribution was shown to have no effect on the critical strain while coatings of high elasticity exhibited high yield strains as expected. The loss modulus demonstrated strain hardening before the elastic to viscous transition. The loss modulus peak was identified by a maximum strain which was significantly lower for a coating based on clay with a high shape factor. The characteristic elastic time was found to vary between 0.6 and 1.3s. The zero shear viscosity of barrier dispersion coatings were estimated from the characteristic elastic time and the characteristic modulus to be of the order of 25-100 Pa s.     

Characterization of surface coatings by the scratch adhesion test and by indentation measurements

Summary Functional coating and surface modified layers can be characterized by engineering related criteria such as the ultramicrohardness test and the scratch adhesion test. The ultramicrohardness test is based on penetration depth measurements during a loading and unloading cycle. The depth sensing indentation provides a means of evaluating the elastic and plastic deformations of the tested material, from which, by calculation, the microhardness, HV, and the elasticity modulus, E, can be derived as illustrated on a number of examples of hard and soft materials and coating composites. The scratch test (REVETEST^R) and microscratch test (MST^R) has been applied to determine the adhesive and/or cohesive strength of coatings deposited on softer or tougher substrates. A Rockwell C diamond cone is used to scratch the surface of the coated or surface-modified specimen at a constant speed and under a continuously increasing load. The smallest load at which the coating is damaged, called the Critical Load, L_c, is determined by optical, electron optical, acoustic emission detection and/or by frictional force measurement, i.e. by the sudden increase of the driving force. This is illustrated on hard, brittle, and on soft coatings.     

Hardness Equation for Ormosils

Hardness of ormosils coating on various kinds of substrates is important, and by considering recent progresses in understanding the hardness of ionic crystals or covalent crystals, new hardness equations for calculating the hardness of glasses or ormosils from chemical compositions were derived. When we applied an indenter to the surface of glass or sol-gel coatings, the surface of indenter is a declined one to the flat surface of glass or coating, thus the applied force should be analyzed by using the shear modulus, S, and Young's modulus, E. This is now well accepted for the analysis of hardness of ionic or covalent bonding inorganic materials. For example, by considering the binding energy and plastic deformation, Gilman showed that Hv of NaCl crystal can be calculated by an equation including elastic stiffness which indicated a good agreement between calculated and observed value. For covalent crystals he reported that the strength of chemical bonds could be correlated with the glide (shear) activation energy for covalent crystals quantitatively. These explanations are basically applied to the hardness of silicate glasses and ormosils. By considering both shear modulus and Young's modulus we have derived equations for calculating the hardness of glasses or ormosils from chemical composition, which includes packing density of atoms and bond energy per unit volume has been taken account. The agreements between calculated and observed hardness values for ormosils were comparatively good.     

Effects of coating composition and surface pre-treatment on the adhesion of organic-inorganic hybrid coatings to low density polyethylene (LDPE) films

Organic-inorganic hybrid coatings, obtained through the sol-gel chemistry from tetraethoxysilane and polyethylene-poly(ethylene glycol) block copolymer, have been prepared in different compositions and applied to untreated and plasma treated LDPE films by spin coating. The mechanical properties of the coatings and the adhesion between coating and substrate have been characterized by fragmentation test. An increase in coating strength, elongation at break and adhesion has been observed with increasing the organic fraction in the hybrid coating. A plasma treatment of the LDPE surface, just before the application of the coating, lead to an increase of the adhesion between coating and substrate (interfacial shear strength), leaving almost unaffected coating strength and strain at fragmentation onset.     

The structure and properties of polymer-metallic coating interphase

The structure of the surface layer in polymers (LDPE and PET) decorated with a thin metal (gold and platinum) layer was studied after their deformation under different conditions. It was found that relatively thick coatings debonded from the polymer substrate during tensile drawing. Debonding was observed at low tensile strains (below 20–30%). During the further drawing of a polymer, a regular microrelief typical of deformable “rigid coating on a soft substrate” systems appeared on its surface. This phenomenon is explained by the fact that the debonding metal coating uncovers not the surface of the pure polymer but a certain modified layer, which has a higher elastic modulus than the pure polymer. The formation of this layer is associated with the inclusion of metal atoms into the polymer during the metal decoration by plasma immersion ion deposition. As a result of this inclusion, a modified layer, which has a higher glass transition temperature, a higher elastic modulus, and other mechanical properties, is formed between the coating and the polymer.     

Preparation of an environmentally friendly antifouling degradable polyurethane coating material based on medium-length fluorinated diols

A novel medium-length fluorinated diols and poly(L-lactide) (PLLA) were synthesized via Michael addition reaction and ring-opening polymerization, respectively. Subsequently, Synthetic medium-length fluorinated diols and PLLA were combined to prepare new polyurethane composites with degradability and low surface energy. The compositional analysis and structural characterization of synthetic materials were characterized by using fourier transform infrared spectroscopy (FT-IR) and proton nuclear magnetic resonance spectra (¹HNMR). Thermogravimetric analysis(TGA) indicated that the introduction of medium-length fluorinated diols improved the thermal stability of the polyurethane. The biodegradation and low surface energy of the polyurethane were investigated by static hydrolysis experiment and water contact angle test. It was found that the degradation rate of the polyurethane increased as measurement time went on when the PLLA content was under 40%, and the water contact angle increased from 71.12° to 108.24° with the increase of fluorine content, which indicated that the degradable and low surface energy polyurethane has a potential as a coating material for a marine antifouling coating application.     

Characterisation of roof tile coating degradation using nano-indentation test and surface profilometry

Nano-science and nano-technology have been extensively explored to develop functional and smart coating systems. In this context, it is important to investigate novel characterisation methodologies for surface feature measurement and evaluation of diverse coating systems at nano and micrometrical scales which cannot be implemented by conventional tests. In this study, nano-indentation test have been carried out to characterise the environmental degradation of a polymer coating on a building material substrate. Multiple locations were selected for nano-indention for analysis and evaluation. It has shown that the coating weathering led to a reduction in deformation depth and an increase of hardness and modulus. Furthermore, the weathering resulted in surface quality degradation, which was characterised by hugely reduced surface homogeneity in terms of standard deviations in deformation, hardness and modulus. The coating degradations were also characterised by surface roughness measurement by profilometry. There were significant differences in surface roughness at the micrometrical scale for coatings with varying environmental degradations. They were quantified in terms of surface roughness statistics. The micro morphologies of the coating were observed by SEM which showed a good agreement with results from nano-indentation test and surface roughness measurement. This study demonstrates that nano-indentation test and surface roughness measurement are viable methodologies to evaluate specialised polymer coating systems and to characterise their degradations at the nano and micrometrical scales.     

无毒海洋防污剂研究进展

综述了无毒海洋防污剂研究进展,从防污活性、机理、特点及应用等方面着手介绍了近年来开发的几种新型无毒天然产物防污剂和人工合成防污剂,并就其发展前景进行了展望;指出开发研制无毒海洋防污剂是海洋防污技术的发展方向之一.     

Accompanying of parameters of color,gloss and hardness on polymeric films coated with pigmented inks cured by different radiation doses of ultraviolet light

In the search for alternatives to traditional paint systems solvent-based, the curing process of polymer coatings by ultraviolet light (UV) has been widely studied and discussed, especially because of their high content of solids and null emission of VOC. In UV-curing technology, organic solvents are replaced by reactive diluents, such as monomers. This paper aims to investigate variations on color, gloss and hardness of print inks cured by different UV radiation doses. The ratio pigment/clear coating was kept constant. The clear coating presented higher average values for König hardness than pigmented ones, indicating that UV-light absorption has been reduced by the presence of pigments. Besides, they have indicated a slight variation in function of cure degree for the studied radiation doses range. The gloss loss related to UV light exposition allows inferring that some degradation occurred at the surface of print ink films.     

Thin Film Elastic Modulus of Degradable Tyrosine-Derived Polycarbonate Biomaterials and Their Blends

The integrity, function, and performance of biomedical devices having thin polymeric coatings are critically dependent on the mechanical properties of the film, including the elastic modulus. In this report, the elastic moduli of several tyrosine-derived polycarbonate thin films, specifically desaminotyrosyl ethyl tyrosine polycarbonates p(DTE carbonate), an iodinated derivative p(I(2)-DTE carbonate), and several discrete blends are measured using a method based on surface wrinkling. The data shows that the elastic modulus does not vary significantly with the blend composition as the weight percentage of p(I(2)-DTE carbonate) increases for films of uniform thickness in the range of 67 to 200 nm. As a function of film thickness, the observed elastic moduli of p(DTE carbonate), p(I(2)-DTE carbonate) and their 50:50 by mass blend show little variation over the range 30 to 200 nm.     

Adhesion between coating layers based on epoxy and silicone

The adhesion between a silicon tie-coat and epoxy primers, used in marine coating systems, has been studied in this work. Six epoxy coatings (with varying chain lengths of the epoxy resins), some of which have shown problems with adhesion to the tie-coat during service life, have been considered. The experimental investigation includes measurements of the surface tension of the tie-coat and the critical surface tensions of the epoxies, topographic investigation of the surfaces of cured epoxy coatings via atomic force microscopy (AFM), and pull-off tests for investigating the strength of adhesion to the silicon/epoxy systems. Calculations for determining the roughness factor of the six epoxy coatings (based on the AFM topographies) and the theoretical work of adhesion have been carried out. The coating surfaces are also characterized based on the van Oss-Good theory. Previous studies on the modulus of elasticity of the polymers involved have also been considered. It was found that adhesion problems might be due to inadequate wetting, the significantly different topographies, and differences in the mechanical strengths of the epoxies. Acid-base interactions calculated from the van Oss-Good theory were found useful in explaining the enhanced adhesion for some epoxy/silicon surfaces.     

Control of cell adhesion by mechanical reinforcement of soft polyelectrolyte films with nanoparticles

Chemical cross-linking is the standard approach to tune the mechanical properties of polymer coatings for cell culture applications. Here we show that the elastic modulus of highly swollen polyelectrolyte films composed of poly(L-lysine) (PLL) and hyaluronic acid (HA) can be changed by more than 1 order of magnitude by addition of gold nanoparticles (AuNPs) in a one-step procedure. This hydrogel-nanoparticle architecture has great potential as a platform for advanced cell engineering application, for example remote release of drugs. As a first step toward utilization of such films for biomedical applications we identify the most favorable polymer/nanoparticle composition for optimized cell adhesion on the films. Using atomic force microscopy (AFM) we determine the following surface parameters that are relevant for cell adhesion, i.e., stiffness, roughness, and protein interactions. Optimized cell adhesion is observed for films with an elastic modulus of about 1 MPa and a surface roughness on the order of 30 nm. The analysis further shows that AuNPs are not incorporated in the HA/PLL bulk but form clusters on the film surface. Combined studies of the elastic modulus and surface topography indicate a cluster percolation threshold at a critical surface coverage above which the film stiffness drastically increases. In this context we also discuss changes in film thickness, material density and swelling ratio due to nanoparticle treatment.