OEM汽车涂装车间技术的环境生命周期评价（一）

生命周期评价（LCA）是一种评价产品系统的环境影响和环境权衡的标准化方法。伊士曼化工公司完成了一项＂从涂料到成品车涂装＂的LCA研究,在该研究中,比较了5种有代表性的OEM汽车涂装车间工艺配置的温室气体（GHG）影响和挥发性有机化合物（VOC）排放性能。涂装车间数据由IHS提供。这些工艺配置包括：1）三涂两烘（3C2B）水性（WB）底色漆和1K罩光清漆;2）3C2B WB底色漆和2K罩光清漆;3）3C2B低固含溶剂型底色漆和1K罩光清漆;4）三涂一烘（3C1B）高固含溶剂型底色漆和1K罩光清漆;5）3C1B WB底色漆和1K罩光清漆。本研究的目标是通过比较通用工艺技术类别来帮助理解差异和制定决策。本研究的结论是,3C1B高固含溶剂型工艺可以实现最低的GHG释放量,同时达到欧洲现行的VOC排放限值35 g/m2。但是,如果世界上某些地区的OEM选择不采用VOC减排技术,那么为了达到排放限值35g/m2,需要采用WB技术。这项LCA研究表明,高固含溶剂型技术是对环境影响最小,有利于可持续性发展的技术,建议政策制定者和利益相关者予以考虑。     

Polyethylene/polyurethane blends for improved paint adhesion

Polyolefins have low free surface energy that prevents good wettability of adhesives or paint emulsions to their surface. This work shows that adhesion of olefin block copolymers (OBC) to a polyurethane-based paint can be significantly improved by blending thermoplastic polyurethane (TPU) into OBC. Furthermore, blend morphologies near the paint/polymer interface, and surface compositions of injection molded plaques, were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy with attenuated total reflectance (FTIR-ATR) in order to explore the underlying mechanism of paint adhesion to TPU/OBC blends. It was found that for 35 wt% and 25 wt% TPU loading, the top paint layer is well-attached at the interface, whereas for 15 wt% loading, there was incomplete wetting of the paint, and a gap between the polymer substrate and paint was apparent. XPS and SEM gave consistent results demonstrating that outermost surface composition of TPU in these blends is slightly higher than in the bulk. It is speculated here that, during painting and the subsequent drying step, polyurethane chains from the paint diffuse into the blend substrate and entangle with TPU in the blend. The entanglement between paint and substrate generates a physical link that provides adhesion.     

Flash IR pre-curing of the decorative layer in metal-flake powder coatings

Metal-flake powder coatings are a special class of metallic paint finishes composed of two superimposed layers: a pigmented decorative base coat and an overlaying transparent protective top coat. In the present investigation, a novel curing procedure for such bilayer coatings is proposed. Flash IR pre-curing of the base coat promotes the formation of a surface diffusion barrier and limits movement of the decorative pigments and metal flakes around their initial positions. Oven baking after deposition of the top coat then completes curing of the bilayer coating. The influence of the IR intensity and irradiation time on the final properties of bilayer coatings was investigated. The visual appearance, surface morphology and scratch resistance were evaluated. Experimental findings revealed that the hybrid IR/oven baking curing procedure is a viable method for obtaining bilayer powder coatings with outstanding properties in a shorter processing time and with considerable energy savings.     

CFD simulation of paint deposition in an air spray process

This work analyzes the mechanism of spray deposition by means of computational fluid dynamics (CFD) in order to reproduce virtually the spraying of a paint gun adopted for use in the automotive industry and to predict paint drop trajectories and film builds on the target surface. The prediction of the flow of the continuous phase was obtained by solving the time averaged Navier-Stokes equations in connection with suitable closure models for turbulence (RNG and Realizable k-ε). The dispersed phase was treated by a Lagrangian approach, by tracking numerically a large number of representative particles from the gun exit to the target surface. The initial conditions for the droplets were estimated from a detailed simulation of the paint jet at the exit of the nozzle. In this way one could evaluate positions and velocities of droplets at impact and estimate the properties of the deposited layer of paint. The method was validated by comparison with experimental data obtained by phase doppler anemometry and, subsequently, the approach was applied to different geometries and operating conditions.     

Contact angle measurements to determine the rate of surface oxidation of artists’ alkyd paints during accelerated photo-ageing

The rate of surface photo-oxidation and changes in polarity of the surfaces of artists’ alkyd paint films were studied by a rapid and novel approach using sessile drop contact angle measurements. The contact angles of distilled water and diiodomethane drops on the film surfaces were measured over a period of 25–2000 h of artificial ageing at 40 °C under an indoor light filtered Xenon light source. Chemical changes on the surfaces of the films were also followed using Fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR). Titanium white artists’ paint samples from three different manufacturers were investigated: Winsor & Newton, Ferrario and Da Vinci Paint Co. As the films aged, there was a decrease in the contact angle and an increase in the polar component of the free surface energy of the paint film surfaces indicating the formation of photo-oxidation products. Such changes correspond well to the chemistry of oil paints, and suggested chemistry of long-alkyd paints, because of their relatively high weight percent of fatty acids.     

The effects of acid rain on the appearance of automotive paint systems studied outdoors and in a new artificial weathering test

A study was performed exposing seven automotive OEM coatings (base coat/clear coat paint systems) outdoors in Jacksonville and to different variants of the acid dew and fog (ADF) test, a new approach to simulating the worst case of the weather conditions in harsh urban and industrial environments. Varying the climatic conditions and the severity of the simulated acid precipitation, a certain variant of the ADF test was found to show a satisfying practice correlation. Profilometric and chemical analysis revealed that the coatings differ in the rate of photodegradation after an acid attack due to the penetration of acid solution.     

无苯退漆剂研究及应用

在涂料涂装施工过程中,需要将无用的漆膜除去.本文通过对比常见的几种退漆方法,针对以往常用的含苯有机溶剂退漆剂存在的选择性强,适用范围窄,挥发性强,退漆速度慢,苯含量高,毒性大等缺点,根据各种涂料树脂及溶剂的物化性能,通过选用国产非苯类芳香烃类溶剂,进行多次配方筛选试验,研制出新型无苯退漆剂.经实验室评定及现场工业应用结果表明,研制的无苯退漆剂克服了原含苯退漆剂存在的缺点,可用于除去硝基、氨基、醇酸、酚醛、聚氨酯、过氯乙烯、丙烯酸、环氧树脂等多种漆膜.适用碳钢、不锈钢、铜、铝及木质家具等多种材料表面漆膜的退除.     

涂层表面形貌形成过程模拟与分析

表面涂层形貌形成过程的定量描述对涂层质量控制效果的提升至关重要,建立了集成蒙特卡罗（Monte Carlo）和计算流体力学（CFD）的混合方法模拟复杂的海量液滴沉积成液膜及其随后的流平过程,并系统研究油漆液滴平均直径、黏度、密度以及表面张力对涂层表面粗糙度、流平速度以及流平时间的影响。模拟结果表明,油漆液滴平均直径增大,涂层初始表面粗糙度增大,流平速度减小,流平时间延长;黏度增大,涂层的初始和最终表面粗糙度增大,流平速度减小,流平时间延长;密度减小,涂层初始表面粗糙度增大,初始流平速度增大,流平时间稍微缩短,对最终表面粗糙度影响不大;表面张力增大,涂层流平速度增大,流平时间缩短,对涂层最终表面粗糙度影响很小。     

Scratch resistant clear coats: development of new testing methods for improved coatings

More and more car manufacturers are now demanding clear coats with improved scratch resistance from their paint suppliers. Some motor companies have developed their own tests, some have chosen a test developed by a paint supplier and others are still looking for their optimum test. The opinion prevails that there should be one test which covers all aspects of realistic damage. However, microscopic photographs and reflow experiments show that two kinds of scratches occur in reality, abrasive as well as non-abrasive, renewable ones. Different standard clear coat systems have different sensitivities to both scratch types. In the scratch tests the rating of the clear coats is divergent, because the ratio of both sorts of scratches differs. We have developed a set of two tests, where each test mainly generates one scratch type. These tests, together with physico-chemical measurements (glass transition onset temperature T_g, laser optical profile scanning, indentation depths) lead to a deeper insight into scratch phenomena. One way to develop a clear coat which is resistant against all kinds of scratching damage is described.     

Dynamics of the wetting process on dielectric barrier discharge (DBD)-treated wood surfaces

Protection and preservation of wood properties in exterior environments can only be ensured if the surface is coated with a paint or varnish. In our experiments a dielectric barrier discharge (DBD) was used as a wood surface pretreatment for improvement of the subsequent deposition of thin paint layers from solutions onto these surfaces. As the adsorption, interfacial interactions and adhesion of paints are strongly dependent on surface wettability, the dynamics of the wetting process were analyzed. The results show that the water contact angle decreases after the DBD treatment, proving a more wettable surface. Additionally, the spreading of paint solution on the DBD-treated surface is more isotropic, showing a lower tendency to elongate along the wood fiber orientation.     

The preparation,characterization and photocatalytic activity of radical-shaped CeO2/ZnO microstructures

This paper uses a wet-chemical precipitation route to prepare radical-shaped ZnO microprisms and to deposit Cerium oxide (CeO₂) on the surface of ZnO, to form CeO₂/ZnO microstructures. The samples are characterized using X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and UV–vis diffuse reflectance spectroscopy. Their catalytic activity is also evaluated using methylene blue (MB) as a detection reagent. CeO₂/ZnO systems exhibit higher UV absorption and transparency in the visible region. The experimental results show that the deposition of CeO₂ nanospecies is successful and that the radical-shaped microstructures of ZnO are well maintained. The CeO₂/ZnO microstructures exhibit a much greater intensity of UV-light absorptivity and much higher photocatalytic activity than those of radical-shaped ZnO microprisms.     

Detrended fluctuation analysis of UV degradation in a polyurethane coating

Changes in the intrinsic structure of paint surfaces resulting from extended UV exposure can significantly alter the appearance of paint due to a breakdown in the resin that binds the pigments and flattening agents. In this study, the coating structure of a solvent-based poly-urethane was analyzed to establish correlations between the intrinsic spatial scaling properties of the coating and UV exposure time. Atomic force microscopy and laser scanning confocal microscopy were employed to map surface structures over a range of scales from 80 nm to 80 εm. The roughness of the polyurethane surface was characterized in terms of scaling exponents using detrended fluctuation analysis to identify long-range, power law relations, and to correct for inhomogeneities in the surface structure. The time-dependence of the roughening process was also determined and correlated with changes in gloss. AMSTA-AR-CCB-TA, Watervliet, NY 12189-4050. Email: majohn@pica.army.mil and pcote@pica.army.mil     

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.     

Evaluation of two new white silicone thermal control paints under atomic oxygen

The exterior optical surfaces of satellites are directly exposed to the harsh space environment. Thermal control paints are resistant to the conditions encountered at low earth orbit (LEO): vacuum, atomic oxygen, thermal cycling, and ultraviolet radiation. In this paper two white paints were prepared by ultrasonic dispersing method for application to space structures. The white paints include zinc-oxide-pigmented silicone elastomer SilGel 612 (U1) and a zinc-oxide-pigmented silicone elastomer RT604 (U2). These coatings are electrically non-conductive. We present the behavior of thermal control paints under atomic oxygen (AO). The effects of AO exposure were studied by the mass loss of paint specimens and complementary techniques including scanning electron microscopy (SEM) and atomic force microscopy (AFM). Also the optical degradation in the reflectance spectra, solar absorptance and thermal emittance for U1 and U2 samples before and after AO exposure were investigated. The paints have promising AO resistance properties that could be suitable for space applications.     

Theoretical analysis and experimental characterization of the TPO/adhesion promoter/paint interface of painted thermoplastic polyolefins (TPO)

Exterior and interior automotive applications of TPO (thermoplastic polyolefin) resins, which are, often, composed of a paint coating over an injection‐molded TPO, have increased interest in the surface chemistry and physics of TPOs. Specifically, the interface system composed of base‐coat paint/adhesion promoter/TPO is of primary importance in controlling the paint adhesion to the TPO. The major, active component in the adhesion promoter is a chlorinated polypropylene (CPO). A theoretical model based on phase thermodynamics and diffusion kinetics resulted in a prediction that the TPO/CPO interface should have a lower bound thickness of about 11 nm and an upper bound of about 400 nm. A battery of experimental strategies to characterize this interface system was discussed. Techniques used were transmission electron microscopy (TEM), atomic force microscopy (AFM) and scanning transmission X‐ray microscopy (STXM). The near‐surface morphology of both unpainted and painted, injection molded TPO plaques exhibited ethylenepropylene rubber particles close to the surface, i.e. within the first 0.1–0.8 micrometer of the TPO surface, and no “overlayer” of transcrystalline polypropylene at the surface of the TPO. Each of these microscopic methods showed that the adhesion promoter/TPO interface was very sharp. The thickness of this interface was measured with respect to the interdiffusion of the CPO and TPO by STXM. The STXM measurements yielded an apparent interface thickness between the adhesion promoter and TPO of 340 ± 80 nm. This was in good agreement with the theoretical predictions.     

Failure modes in organic coatings studied by scanning acoustic microscopy

Scanning acoustic microscopy (SAM) has been found to be well suited to study physically and chemically induced changes and defects in polymer coatings exposed to corrosive environments. In this work, SAM was used to investigate sub-surface migration and blister formation in polymer coatings of different layer structure after exposure to a corrosive solution. Two model systems consisting of base coat and clear coat on steel substrates where studied. The time evolution of sub-surface migration fronts and blister initiation and their growth were investigated by analysing SAM images after different exposure times. Depending on the layer structure, it was possible to differentiate between transport of the electrolyte solution (i) through the coating and (ii) along the coating/substrate interface. Samples without clear coat typically showed randomly distributed blisters at the coating/substrate interface, irrespective of the location of initial defects. The random distribution of blisters is related to diffusion of the electrolyte solution through the coating layer followed by “nucleation” at weak spots of the substrate, at the interface between polymer and substrate or within the polymer. In contrast, samples with a clear coat acting as a diffusion barrier showed a sub-surface migration front of 2–4 μm height, propagating along the coating/substrate interface, starting at initial defects. The linear propagation of this front cannot be explained by Fickian diffusion and is discussed in terms of an accelerated diffusion or crack growth kinetics. Since blistering started only at regions, where the migration front has already passed, the presence of electrolyte solution or water at the coating/substrate interface was found to be a prerequisite for the nucleation of blisters.     

Nanocoating individual cohesive boron nitride particles in a fluidized bed by ALD

Experiments are conducted with alumina (Al₂O₃) deposition on a wide size range of hexagonal boron nitride (BN) platelet-like particles. Successful deposition of alumina films on these particles, with film thickness controllable at the Angstrom level, is observed based upon TEM imaging, ICP-AES, particle size distributions, and surface area analysis. While fluidizing, fine BN particles aggregate in the bed. The aggregates are the entities fluidizing, not the primary particles. However, individual particles are coated using Atomic Layer Deposition (ALD), not aggregates. Since ALD is a surface chemistry phenomenon, the films grow uniformly on every primary particle. BN particles are small platelets with different functional groups on the basal planes and edge planes. A small exposure to reagents [2.5×10⁶ Langmuir (L) per reagent per cycle], will only coat the edge planes of uncoated BN particles. A larger dose of 1×10⁸ L will coat the entire uncoated BN particle (edge and basal planes). After 10 ALD cycles of the 1×10⁸ L dose, the exposures can be reduced to 1×10⁶ L as the film is then growing on alumina and not BN. Peel strength data indicate that adhesion between the coated particles and a cured epoxy in a filled composite is ∼25% stronger than that of uncoated particles and the epoxy. The overall thermal conductivity drops ∼17% for an identical filler loading as expected due to the additional thermal resistance added by the film. However, the viscosity of an epoxy resin loaded with coated BN is as much as five times lower than that of the resin loaded with the same amount of uncoated BN. These results indicate that the loading of Al₂O₃ nanocoated BN particles in an epoxy matrix can be substantially increased relative to that of uncoated particles. The thermal conductivity of the more highly filled composite will be increased without adversely impacting filled resin viscosity or the peel strength of the cured material. This is the first reported study indicating that cohesive primary particles that fluidize as aggregates in a fluidized bed can be individually coated with a nano-thick ceramic film using ALD.     

水性罩光清漆固化反应速率及漆膜性能研究

水性罩光清漆固化反应速率对于以“湿碰湿”工艺施工的水性三涂一烘（3C1B）体系有很大影响,水性罩光清漆的固化反应速率主要由作为交联剂的氨基树脂所控制。本文对 3种不同类型的氨基树脂进行了红外表征（ FT-IR）,分析了其分子结构。分别以上述氨基树脂作为交联剂制备水性罩光清漆,通过旋转流变仪测试清漆在固化过程中剪切储存模量的变化,探究了上述氨基树脂对水性罩光清漆固化反应速率的影响。对比了所制备的水性罩光清漆搭配水性 3C1B中涂和色漆的漆膜性能,分析了氨基树脂对漆膜性能的影响。研究结果表明：以甲醚丁醚混合醚化的氨基树脂作为交联剂的水性罩光清漆的固化速率适用于 3C1B体系,且制备的漆膜性能最佳。     

Surface functionalization of polymer nanofibers by ITO sputter coating

In this study, transparent conductive films of tin-doped indium oxide (ITO) were deposited onto the polyamide 6 (PA6) nanofiber substrates at room temperature. Atomic force microscopy (AFM) was employed to study the morphology of the nanofibers, respectively. The AFM results indicated a significant change in the morphology of the nanofibers before and after the ITO sputter coatings. The light transmittance and surface conductivity of the ITO-deposited nanofibers were also investigated. It was found that the surface resistivity of the PA6 nanofiber with the ITO deposition had a significant drop and the ITO deposition obviously affected the light transmittance of the PA6 nanofibers.     

Prediction of spectral reflectance factor distribution of automotive paint finishes

It is necessary to determine the accurate reflectance of painted surfaces for the review of paint finishes by computer graphics (CG) before actual painting of the exterior color of automobiles, and for quality control during production and inspection processes. We have optimized a method for measuring reflectance by using a statistical technique. We have found that the reflectance of a painted surface is best measured at an incident angle of 60° and at five aspecular angles of 10°, 18°, 28°, 40°, and 90°. Our method makes it possible to accurately reproduce reflection characteristics of paint finishes containing special flake pigments, such as pearl mica. Also it was proved that our method can apply not only to solid and metallic coatings but to all painted surfaces. © 2005 Wiley Periodicals, Inc. Col Res Appl, 30, 275–282, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col.20125