Simulations and experimental investigation of paint film leveling

The surface structure of a paint film is the result of the interplay of a variety of physical influences, e.g., the superposition of droplets during spray application, the surface tension-driven leveling, and the viscosity increase in the leveling phase. A numerical simulation program is presented that incorporates all the relevant mechanisms of paint film structure formation during and after spray application. The simulation program was validated by comparing simulations and leveling experiments. The influence of the initial film geometry and viscosity on the leveling behavior is demonstrated. For the investigations, model liquids and commercial paints with an increasing complexity of the physical properties were chosen: Newtonian flow behavior without solvent evaporation, Newtonian flow behavior with solvent evaporation, viscoelastic paints with non-Newtonian flow behavior. Four variants are proposed regarding how thixotropy can be measured and how a mathematical model can be created. The advantages and disadvantages of the variants with regard to the implementation of thixotropy in the simulations are listed. A method to predict the leveling behavior of thixotropic paints with simultaneous recovery of the viscous and elastic properties from rheological measurements using discrete relaxation time spectra is presented.     

漆膜干燥性能的测定方法

漆膜的干燥性能非常重要.本文简要介绍了漆膜干燥时间的测定方法,包括表干时间、实干时间以及回黏性、无印痕和码垛性试验方法.     

Contact angle characteristics and breaking strength of paint plastic film

The advancing contact angle of water on plastic film coatings on metal was measured against both the air and the metal side surfaces after their being peeled off from the metal substrate. The plastic used was a methacrylate copolymer, and it was baked on cadmium, aluminum, nickel, iron, and gold. Contact angle for the air side was about 74° at 25°C. for all metals, but the values on the metal side differed considerably, ranging from 76° for gold to 50° for cadmium. At the same time the static breaking strengths of the same films were investigated by applying a knife-edge vertically to the film with increasing load and measuring the weight at which the electric resistance through the film became zero. Increasing film thickness gave increasing strength, but further thickening made the film weaker with a tendency for crack formation. The film–metal combinations of larger contact angle difference generally also showed the higher breaking strength.     

Self-opacifying aluminum phosphate particles for paint film pigmentation

Conclusion  Opaque particles of aluminum phosphate can be obtained in two ways: self-opacification within drying latex films and thermal treatment at 500–700°C (which was previously described). Self-opacification is easily achieved and allows for extensive replacement of TiO₂ as a white pigment, with a gain (in an acrylic latex) in the optical properties of the pigmented film. Universidade Estadual de Campinas, 13083-970 Campinas SP, Brazil. MARISA MASUMI BEPPU is a graduate student in the School of Chemical Engineering at the State University of Campinas, Brazil. Her dissertation deals with inorganic phosphate salt optical and colloidal properties. EMíLIA CELMA DE OLIVEIRA LIMA is an Assistant Professor of Chemistry at the Federal University of Goiás, in Goiania, Brazil. She has been working in the field of inorganic particles and gels since 1989 and received two awards for her work; one at the Seventh International Conference on Colloid and Surface Science, in Compiègne, 1991, and the other was given by the Brazilian Association of Paint Makers (Abrafati) for her work on the making of hollow particles. RENATO MASSAMI SASSAKI is a graduate student in the Institute of Chemistry at the State University of Campinas, Brazil. His dissertation deals with morphological characterization of porous materials. FERNANDO GALEMBECK serves as the Head of the Institute of Chemistry and as Professor of Physical Chemistry at the State University of Campinas, where he has been since 1980. His areas of research include surfactants, pigments, and polymers. Dr. Galembeck has authored approximately 100 research papers in refereed journals.     

Antimicrobial and anti-quorum-sensing properties and paint film usage of novel diazaborine-based copolymers

To meet high hygiene requirements, intensive studies are being carried out on antimicrobial materials. This study reports the synthesis of 3-((1-hydroxybenzo[d][1,2,3]diazaborinin-2(1H)-yl)sulfonyl)propyl methacrylate (DAZBMA) and its polymer, which is antimicrobial [tested with Staphylococcus aureus (ATCC 25923 and MU 40) and Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, and Candida albicans ATCC 10239] on solid surfaces. Antibiofilm capability was tested against MU 40. Although DAZBMA and its polymer show a high quorum-sensing inhibition property (tested with Chromobacterium violaceum CV 026 and CV 12472 and P. aeruginosa PA01), the lesser antibacterial activity of the polymer was improved by copolymerizing DAZBMA with quaternized 2-dimethylaminoethyl methacrylate. The paint films containing the prepared copolymer are highly active against all tested bacteria and show an antibiofilm effect against hospital-acquired multiple-antibiotic-resistant MU 40. The novel copolymer can be used in water-soluble paints to reduce its biofilm production and pathogenicity, especially for paints used in hospitals. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 46907.     

芳香族聚噁二唑纤维的酸老化行为及降解机理研究

研究了芳香族聚-1,3,4-噁二唑(POD)纤维浸泡于不同酸溶液中的力学性能和表面形貌的变化,表征了酸老化前后POD纤维的聚集态结构与分子结构,探讨了POD纤维的酸老化机理.结果表明:POD纤维力学性能在体积分数30％的硫酸溶液中下降最快,在硝酸溶液中老化最严重;POD纤维老化后线密度变大,温度越高,力学性能下降越快;...     

mLLDPE薄膜的光氧化及热力学降解

茂金属线型低密度聚乙烯(mLLDPE)和传统线型低密度聚乙烯(LLDPE)薄膜经紫外灯照射不同时间后,用红外光谱和差示扫描量热法对薄膜跟踪测试。发现mLLDPE的羰基指数及不饱和碳碳双键的变化快于LLDPE;mLLDPE的氧化初始温度及熔融热焓的变化也明显低于LLDPE。     

Crystal morphology of organic pigments and rheology of dispersions in ink and paint media

The purpose of this work is to establish relationships between physico-chemical character of pigments and rheological behaviour of dispersions under steady shear conditions. It has been found that the approximately cube-shaped crystals of CI Pigment Yellow 13-type pigments disperse substantially as individual crystals in (highly viscous) lithographic ink media; strength of structure and plastic viscosity relate simply to number concentration of crystals and area of the pigment/medium interface, respectively. Interpretation of data for dispersions of Red 57.1 pigments in similar media is complicated by persistent face-to-face aggregation of their rectangular plate-shaped crystals. In dispersions of metal-free monoazo pigments (Yellows 1 and 74, Reds 3 and 112) in decorative paint media (relatively low viscosity) strength of structure shows a markedly increased dependence on pigment concentration above a critical concentration. This concentration is different for each pigment and is determined primarily by crystal shape, the less cube-shaped the crystals the lower the critical concentration. Plastic viscosity is dependent upon area of the pigment/medium interface and thickness of adsorbed layer of paint medium.     

重防腐涂料涂装后涂膜主要弊病分析

对重防腐涂料涂装后形成的流挂、针孔、干喷、缩孔、裂纹、发白等6种漆膜弊病的原因进行了分析,提出了预防措施和修补办法.     

战国早期皮甲胄漆膜检测与研究

本文选取曾侯乙墓出土已自然干燥的3个甲胄残片的漆膜样品,采用三维视频显微镜、扫描电镜能谱分析、红外光谱分析、拉曼分析等现代仪器分析方法,针对漆膜形貌、分层结构与组成成分等进行研究。发现曾侯乙墓的甲胄漆膜的成膜成分主要为大漆;红色漆膜的主要显色成分为朱砂;黑色漆膜为大漆自然显色,未添加石墨;漆器存在多次髹涂的工艺;未发现漆灰层。     

完全降解水溶性薄膜的制备

本文在选择好适宜的成膜料的基础上,以淀粉为主体材料,添加适当的增塑剂、防黏剂、表面活性剂、快干剂、水等,通过流延法成型而制备了可完全降解型水溶性薄膜。     

Accelerated degradation of a chlorinated rubber paint system applied over rusted steel

Chlorinated rubber coatings have proved to be effective anticorrosion materials for steel structures. However, their formulation and manufacture must be undertaken with extreme care — particularly as regards the chlorination process and the stabilizers and plasticizers added — in order to avoid early failures. This paper reports on the premature failure of a chlorinated rubber system that was applied directly over uncontaminated rusted steel. The accelerated formation of rust at the steel/paint interface rapidly resulted in complete degradation of the organic coating. Interfacial rust appears to catalyze the cleavage of the C-Cl covalent bonds in the polymer, which gives rise to the formation of chloride ions. These in turn have a dramatic accelerating effect on the corrosion of the base steel, thereby deteriorating the paint system.     

Polymer degradation in porous media flow

The hydrodynamic degradation of high molecular weight poly(acrylamide-co-Na acrylate) in 1M NaCl in porous media flow was studied as a function of polymer concentration in the dilute and semidilute concentration ranges. Porous media rheometry was used to monitor molecular weight changes due to chain scission. At equivalent superficial velocities of flow through a glass bead pack, polymers at dilute concentrations showed greater loss of molecular weight than polymers at semidilute concentrations.     

石蜡熔点对PE漆漆膜质量的影响

分析石蜡熔点影响四PE漆漆膜质量的原因，指导施工者根据不同的施工环境选择适当的石蜡。     

环氧带锈涂层在干湿交替环境中失效过程的电化学阻抗谱

应用电化学阻抗谱(EIS)技术研究了浸泡在3.5%NaCl溶液中的环氧带锈涂层在干湿交替条件下的劣化过程。结果表明,干湿交替环境下环氧带锈涂层的阻抗变化与全浸环境类似,表现为3个阶段:阻抗迅速降低阶段,缓慢降低阶段和最后的失效阶段,但干湿交替环境中涂层阻抗值比全浸环境要低两个数量级,涂层电容则约高一个数量级,涂层失效速率明显高于全浸泡环境下的失效速率。环氧带锈涂层在干湿交替环境下的失效原因,主要可归因于干湿交替循环使涂层发生溶胀与收缩,增加了涂层的孔隙率;此外,干湿交替状态也会促进氧向涂层/金属界面的渗透,从而加速基体金属的腐蚀并加快涂层的失效过程。     

Effects of mechanical properties of paint film on the forming of pre-painted steel sheets

Formability is one of the most important factors for pre-painted steel sheets (PCMs). Both high formability of the steel substrate and high integrity of the paint films on it after processing are required. In this study, elongation, tensile strength and elastic strain energy of various paint films were examined by tensile test, and the relationship between the mechanical properties of paint films and the integrity of paint films of PCM after bending and drawing were studied. We found that the required properties of paint films of PCM depended on the forming mode. In the bending mode, in which steel sheets were mainly subjected to tensile strain, the damage of paint films was dominated by the maximum strain and the tensile strength of the paint films. The paint films having higher maximum strain and higher tensile strength had better formability in bending. On the other hand, the damage of paint films was dominated by the maximum strain of paint films and elastic strain energy stored in paint films after deformation in the drawing mode in which steel sheets were subjected to tensile and compressive strain. The paint films having higher maximum strain and lower elastic strain energy had better formability in drawing. The relationship between the lubrication attributes of paint films and the limit of drawing ratio (LDR) of PCM was also studied. It was observed that the PCM with paint films having low friction coefficient had a higher LDR and it was the same ratio as the unpainted substrates.     

Investigations of the drying process of a water based paint film for automotive applications

In a cooperative research project funded by the German BMBF the drying process in the automotive industry has been investigated. More precisely, it was the aim of the project to develop a simulation program that in its final stage allows the calculation of the heat-up process of a fully painted car body, including heat and mass transfer in the thin, water based paint film. The investigations focused on the joint base coat and clear coat drying process used in the automotive industry.A physical model was developed that treats mass and heat transfer of a ternary mixture applied as a thin film on a substrate. This model was added to the commercial CFD-Solver ANSYS-FLUENT and successfully compared with experimental data in practical conditions. The estimation of paint failures, i.e. pinholes that might occur due to unfavourable drying, which is based upon an empirical model applying a design-of-experiments scheme, was also added to the CFD-Solver.     

Modelling film formation and degradation of semi-transparent exterior wood coatings

Deposition and aggregation of small solid particles are encountered in many natural and industrial environments. These processes are of substantial significance for the development of a coating film on a wooden substrate. Formulating new coatings with improved performance and lower cost for exterior wooden joinery, mainly a trial-and-error approach, has a large influence on the initial film forming stage in a coating's life. Therefore modelling can supply insight in the particle–particle–substrate interaction. Two approaches are proposed. The first one uses a random point process to position the cluster centres and particles in a dry film. The second strategy starts with a random scattering of the particles in a wet film followed by Monte Carlo sampling and subsequently minimization of the total energy of the particle system. Surface roughness and gloss are calculated from the simulated surface structure. Next to these simulations, surface reconstruction of coated wood with confocal scanning laser microscopy (CSLM) is used to obtain surface roughness values and deduction of gloss applying the bidirectional reflection distribution function (BRDF) theory. As semi-transparent systems are the subject of gloss calculation on surfaces measured by CSLM and computer simulation, refractive index is estimated using an analytical solution of the reflectance and transmittance problem. Withal, coating and subsequent degradation simulation can become a valuable tool for screening purposes.