Determination of the impact of cellulose ester molecular weight on the drying behavior of automotive refinish basecoats

In the case of automotive refinish basecoat formulations, anti-sag and dry-to-touch are very important requirements. A series of experiments were outlined to investigate the impact of cellulose acetate butyrate (CAB) on the drying behavior of refinish formulations using thermogravimetric analysis (TGA). The goal was to ascertain whether the chemical nature and the molecular weight of the cellulose ester had any impact on solvent losses during the film formation process. Automotive refinish formulas were prepared containing different grades of CAB. Two approaches were adopted for the initial set of experiments. The first batch of samples was prepared at the same application viscosity (iso-viscosity) which meant that the solids level varied depending on the molecular weight of CAB that was used. The second set had identical solids level (iso-solids) which in turn caused the viscosity to be dependent on the grade of CAB.     

溶剂及施工工艺对3C1B水性面漆外观影响研究

水性 3C1B（三涂一烘）工艺是以湿碰湿的方式喷涂水性中涂、水性面漆和清漆,并一次性烘干的工艺,可以显著降低能源损耗,提高生产效率。涂层外观是评价涂料质量和涂装效果的重要指标之一,而湿碰湿工艺的这种特殊的施工方式对涂层的外观表现更为敏感。本文以水性白实色涂料为例,从中涂、面漆的材料配方及施工工艺等方面对水性 3C1B汽车涂料的外观改进进行了研究,并识别出了关键影响因素,结果表明：水性面漆对漆膜整体外观的影响大于中涂;配方的干湿及喷涂雾化后的干湿对漆膜流平、流挂等影响较大,进而会影响漆膜的外观表现。     

Evaluation of the weathering performance of basecoat/clearcoat automotive paint systems by electrochemical properties measurements

The aim of the present study was to investigate the possibility of evaluating the weathering performance of a basecoat/clearcoat automotive paint system through the determination of its electrochemical properties. To this end, the electrochemical properties of a basecoat/clearcoat automotive paint in a 3.5% solution of NaCl in deionized water were measured at different weathering exposure times. A constant phase element (CPE) was used for describing the electrochemical behavior of the coatings under test. The values of the CPE parameters, i.e. Y₀ (the CPE constant) and n (the CPE power) were subsequently correlated to the extent of photo-oxidation (as measured by appearance, surface roughness, FTIR, surface tension and adhesion measurements) of clearcoat at the surface, in the bulk and at the interface between the basecoat and the clearcoat. The result showed that the electrochemical parameters Y₀ and n provide ready means for comparing the weathering performances of basecoat/clearcoat automotive paint systems. Increases in the value of Y₀ together with decreases in the value of n with increasing weathering exposure times suggest increased possibilities for the onset of cracking in the clearcoat itself in addition to its propagation towards the basecoat. Additionally, sudden variations in the values of Y₀ and n are indicative of increases for the clearcoat to peel off.     

我国汽车涂料的研究进展

综述了我国汽车涂料的分类。重点介绍了汽车底漆、中间漆、面漆、罩光清漆和修补漆的研究进展。指出了今后我国汽车涂料的发展方向。     

On the combined use of UVA, HALS, photooxidation, and fracture energy measurements to anticipate the long-term weathering performance of clearcoat/basecoat automotive paint systems

Transmission UV spectroscopy measurements of clearcoat ul traviol et light absorber (UVA) disposition, electronspin resonance (ESR) spectroscopy measurements of clearcoat and basecoat Active hindered amine light stabilizer (HALS) disposition, and transmission Fourier transform infrared (FTIR) measurements of photooxidation have been carried out on 5 μm thickslioes of clearcoat/basecoat/primer/e-coatpaint systems on steel panels as a function of outdoor exposure. These analysis results are combined with clearcoat fracture energy measurements to assess the possibility that a clearcoat/basecoat paint system will resistcatastrophic cracking/peeling failure at long times. Taken together, all results indicate that these nontraditional paint weathering performance metrics should be added to the existing repertoire of paint weathering performancemetrics to ensure that inferior clearcoat/basecoat automotive paint systems are not introduced into service. Ford Research Laboratory, MD 3182SRL, P.O. Box 2053. Dearborn, MI 48124     

中国重汽卡车免中涂车身漆膜外观品质提升方法探究

重卡车身取消中涂后涂装面漆存在漆膜外观质量下降的问题。本文立足中国重汽卡车公司实际生产,从电泳和面漆涂装两方面结合施工工艺与设备探讨了在卡车车身取消中涂后提升面漆漆膜外观品质的方法。重点探讨了如何通过改善前处理和电泳涂装的工艺与设备来降低电泳漆膜表面粗糙度,以及如何通过优化面漆施工参数和提高油漆施工性能来提升面漆外观,从而达到提升免中涂车身漆膜外观品质的目的。     

我国汽车修补漆市场概况及其发展趋势

简述了我国汽车修补漆的市场现状及其动向,并指出其发展趋势。     

汽车修补漆用高固体分丙烯酸树脂的研究

随着全球降低涂料中VOC含量的环境法规出台,汽车修补漆正由传统溶剂型涂料向高固体分、水性化方向发展。通过丙烯酸单体、引发剂、链转移剂和合成条件的选择,开发了一种黏度适中的固体分达70%的丙烯酸树脂。该树脂与异氰酸酯固化剂配合应用于汽车修补漆,其性能完全达到市售国外同类树脂的水平。     

Application of microcalorimetry to the study of interactions in coating formulations

Water-based coating formulations contain many components, such as latex binder, pigment, dispersant, thickener, and surfactant. Complex interactions between these components affect properties of the coating in both the wet and dried states. For example, rheology of the paint is dependent on the interactions of components in the formulation. Pigment interaction can affect the degree of dispersion and, therefore, have ramifications on end use properties such as hiding and tint strength of the paint film. Isothermal titration calorimetry has been used to determine the enthalpy of interaction of the coating components. Representative examples will be given to demonstrate structure–property relationships that correlate the interactions of latex, pigment, surfactant, dispersant, and thickener with paint viscosity as well as end use performance parameters such as adhesion and tint strength.     

Preparation,characterization, and analysis of anti-corrosion subsea coatings

Within this work, a two-component anti-corrosive epoxy primer formulation, Sigmacover? 280, and its resulting films were prepared and evaluated. The optimum coating time following formulation was extended by adding an appropriate amount of solvent as a controlled thinner. The draw down coating method was identified to be a reproducible and a robust paint film deposition process. Gravimetric analysis, Differential scanning calorimetry (DSC), and through-dry testing were used in the characterization of the curing and drying behavior of each applied primer film. The shortest time for achieving a through-dry state occurred with thinner films cured at the higher temperature, as seen in the film curing/drying. The minimum covercoating time and full cure time of the paint films, cured under the different conditions, were evaluated by means of its dryness, hardness, and curing state studies/characterization.     

Microstructure–property–quality‐correlated paint design: An LMC‐based approach

Paint is designed to offer various chemical and physical properties for surface protection, styling, and appearance. Nevertheless, the anticipated quality of the surface coating is frequently unsatisfactory, which is often attributed to paint formulation. As new demands on coating performance continuously emerge, paint formulation design becomes much more challenging than ever. It is recognized that paint design can be significantly improved with the help of advanced computational methods, as they can provide great freedom and control over the investigation of paint formulation through any number of in silico experiments virtually under any application conditions. This article introduces a lattice Monte Carlo based computational methodology for paint formulation design. By this methodology and structural analysis techniques, a variety of correlations among paint material, curing condition, coating microstructure, and coating qualities can be generated, which are critical for the development of superior paint formulations. A comprehensive study on acrylic‐melamine‐based paint design and analysis demonstrates the methodological efficacy. © 2008 American Institute of Chemical Engineers AIChE J, 2009     

浅谈汽车涂装工艺用电管理

涂装车间是汽车制造工艺中的耗电大户,有效控制涂装车间的电耗,可降低汽车制造的动能成本。以烘干炉、喷漆室供排风设备为例讨论如何降低电耗。     

Effect of particle size distribution on the performance of two-component water-reducible acrylic polyurethane coatings using tertiary polyisocyanate crosslinkers

A two-component waterborne polyurethane system with a 250 g/l VOC has been formulated to meet the performance requirements of the automotive refinish market. This paper discusses an experimental study to develop a two-component water-reducible polyurethane coating using a tertiary aliphatic polyisocyanate crosslinker with dry times, appearance, and reactivity equivalent to a two-component solventborne system. The effects of acrylic polyol monomer composition, glass transition temperature (T_g), and hydroxyl concentration on drytime and ambient cure film performance have been determined. The effects of particle size distribution of the formulated coating on performance were examined. It was found that smaller particle size provides overall improved film properties, i.e., faster dry time, increased hardness, and faster development of solvent resistance. The relationships of both acrylic polyol composition and formulation variables on the particle size distribution are discussed. Presented at 76th Annual Meeting of FSCT in New Orleans, LA, on Oct. 11–16, 1998. 1937 West Main Street, Stamford, CT 06904.     

汽车修补漆雨后起泡问题解析

通过对汽车修补漆漆膜起泡弊病的调查与分析,设定了相应的实验方案,证实汗液是造成此问题的原因,而原子灰的存在则使此种危害更加严重。通过增加工艺要求,经试验验证及实践,解决了该问题。     

An improved accelerated weathering protocol to anticipate Florida exposure behavior of coatings

A new accelerated weathering protocol has been developed which closely replicates the performance of automotive and aerospace coating systems exposed in South Florida. IR spectroscopy was used to verify that the chemical composition changes that occurred during accelerated weathering in devices with a glass filter that produced a high fidelity reproduction of sunlight’s UV spectrum matched those that occurred during natural weathering. Gravimetric water absorption measurements were used to tune the volume of water absorption during accelerated weathering to match that which occurred during natural weathering in South Florida. The frequency of water exposure was then scaled to the appropriate UV dose. A variety of coating systems were used to verify the correlation between the physical failures observed in the accelerated weathering protocol and natural weathering in South Florida. The new accelerated weathering protocol correctly reproduced gloss loss, delamination, cracking, blistering, and good performance in a variety of diverse coating systems. For automotive basecoat/clearcoat paint systems, the new weathering protocol shows significant acceleration over both Florida and previous accelerated weathering tests. For monocoat aerospace systems, the new weathering protocol showed less acceleration than for automotive coatings, but was still an improvement over previous accelerated tests and was faster than Florida exposure.     

The effect of clear coat and basecoat interdiffusion on the appearance of automotive coating system

In this study, the possible effect of clear coat and basecoat interdiffusion on final appearance of the coating system is examined. The clear coat was applied at different thicknesses wet on wet on the basecoat. The orientation of aluminum flakes was evaluated by the orientation distribution and the flop index measured by the goniospectrophotometer. The gloss, haze, specular reflectance, distinctness of image and orange peel attributes were measured by the goniophotometer and the orange peel analyzer, respectively. The obtained results indicated that the clear coat thickness had no influence on the orientation distribution and the flop index, while the other measured appearance attributes were under influence of clear coat thickness. Optimal appearance attributes were achieved at 75.3 ± 1.8 μm of the clear coat. In addition, the texture analysis was performed on the images of the coatings. No variation in texture was found by increasing the clear coat thickness. Based on the appearance measurement results, it seems that interdiffusion of the basecoat and clear coat has negligible impact on the appearance of the coating system.     

Implementing DOE to study the effect of paint application parameters, film build, and dehydration temperature on solvent pop

This research investigated popping when automotive clearcoat was applied over waterborne basecoats using design of experiments (DOE). The study was conducted using melamine crosslinked acrylic latex basecoat and acrylic acid/epoxy clearcoat. The focus of the project was directed toward the paint application and dehydration stages. The study was conducted in four phases. In Phase 1, three paint application parameters, flow rate (FR), atomizing air (AA), and distance of the applicator tip from the substrate (D), were investigated. In Phase 2, FR and target distance were investigated in relation to popping while keeping other parameters as well as film build constant. In Phase 3, the effect of film build on popping was investigated by selecting three levels of film build. Phase 4 was focused on the possible effect of dehydration oven temperature on popping. Results indicated that FR does not affect popping directly. However, it significantly affects the film build. Both film build and dehydration oven temperature were found significant in relation to popping occurrences. This work suggests that dehydration oven temperature and film build affect solvent popping. Although this study identified the significant factors causing waterborne basecoat popping, conditions for a pop-free paint surface were not established.     

Modeling, prediction, and analysis of alkyd enamel coating properties via neural computing

The use of artificial neural networks (ANNs) in the modeling and prediction of alkyd enamel coating properties, as well as in the sensitivity analysis that can be performed between the properties and the different paint components, are described. A feedforward neural network with sigmoidal activation functions was used with a conjugate gradient algorithm to recognize the complex input-output relation between the paint properties and the formula components. We restricted the study to only two properties of alkyd enamel paints: gloss and drying time. A database of five different families of alkyd enamel paints, containing the different components of the formulations as well as process information, was used in this study. The results obtained show, within the expected uncertainty tolerance, that predictive power of more than 90% for these two properties can be achieved. A sensitivity analysis was also performed using ANNs, yielding the relative importance of the different components of the formulation on the properties of the enamel coatings, which agrees with experience for gloss but gives mixed results for the drying time (apparently due to the high uncertainties in the measurement of this property).     

Waterborne latex coatings of color: II. Surfactant influences on color development and viscosity

A matrix of coating variables, nonassociative versus associative thickeners, different latex median particle sizes, individual surfactants and colorants [carbon black (CB), red, and yellow pigments], was examined for their influence on variances in coatings rheology and color development. Within the different coating groups, the variable of interest in this study was the surfactant added to the colorant formulation. In all three colorant formulations, sodium dodecyl sulfate (an anionic surfactant) provided poorer color development (CD) than in applied formulations containing an equivalent nonylphenol oxyethylene (EO) surfactant. In CB formulations, nonionic surfactants with higher EO content provide improved color development at low (2 mM) concentrations, but near equality in CD is achieved with low EO surfactants at higher concentrations. In contrast to CB formulations, red and yellow colorants exhibit good color development with high EO content nonionic surfactants only at low nonionic surfactants concentrations. This variance appears to be related to the interactions of surfactants with inorganic pigments (talc and laponite) in the colorant formulation. The coating’s rheology is related to latex, thickeners, and surfactant components of the paint, as has been noted in previous studies, but not to the nature of the color pigment. The viscosity of the hydroxyethyl cellulose (nonassociative type) and HEUR (associative type) thickened paint decreased with colorant addition due to dilution effects. There were no unusual deviations with the NP(EO)_x surfactants, except when a large hydrophobe nonionic surfactant [e.g., C₁₈H₃₇(EO)₁₀₀] is added. In HEC thickened coatings, the viscosity decreases when C₁₈H₃₇-(EO)₁₀₀ is in the colorant due to that surfactant inhibiting depletion flocculation. In the C₁₈H₃₇(EO)₁₀₀ coatings containing the HEUR thickener, significant increases in viscosity were observed, above the dilution values observed with the colorant addition. This is related to the viscosity maximum in the low concentration of HEUR with the C₁₈H₃₇(EO)₁₀₀ surfactant. Color development is independent of the viscosity profile of the coating. Presented in part at the 81st Annual Meeting of the Federation of Societies for Coatings Technology, November 13–14, 2003 in Philadelphia, PA.     

绿色颜料在高性能涂料中的应用

该文阐述了绿色无机颜料和绿色有机颜料在氟碳涂料、高级建筑涂料、重防腐蚀涂料、汽车涂料、卷材涂料、隔热反射涂料、示温涂料、导电涂料等高性能涂料以及对环境友好的水性涂料、粉末涂料、紫外光固化涂料等领域的应用。