Scratch resistance of ‘fast-cured’ metal flake powder coatings

The economy of high quality metal flakes powder coatings process is remarkably influenced by the curing procedure involving two cost and time consuming steps in convective oven. Significant savings can be achieved accelerating the baking process by IR pre-curing the outermost layers of the basecoat and following this with a conventional oven-baking of the whole coating system. In the present investigation, the IR pre-curing process of the basecoat was analyzed by studying the influence of the IR radiation intensity and exposure time on the adhesion strength and scratch resistance of the coating varying the contact load of the scratching indenter.     

Effects of IR pre-curing conditions on wear resistance of metal flake powder coatings

Hybrid IR/convective oven baking of high quality industrial powder coatings is one of the most attractive method to achieve significant economic and process time savings. This method is based on two curing steps: at first, a pigmented decorative basecoat is electrostatically sprayed and, then, pre-cured with IR-radiation, secondly, a transparent protective topcoat is sprayed on the basecoat and the resulting bilayer coating is oven baked. The optimization of the IR pre-curing conditions and the correlation between the effect of polymerization degree of the basecoat and the wear resistance of the whole coating system are investigated. In particular, an experimental study in which the degree of chemical conversion of the pigmented basecoat, the overall coating morphology and its thermal, mechanical and tribological properties are analyzed in the light of IR-radiation time and power, has been carried out. Experimental results show that the intermediate range of curing time and IR power investigated leads to properly cured basecoats and subsequently to better morphological, mechanical and tribological behavior of the whole coating system. These results were also validated by comparison with the coatings cross-linked by the traditional two-step oven baking process.     

金属粉末涂料概述

介绍了金属粉末涂料的分类、配方、生产制造与施工工艺,对其最新研究成果进行了展望,表明金属粉末涂料具有良好的发展前景。     

锌薄片抗腐蚀涂层

目前,在文献和专利中已经有大量的基于锌/铝薄片制成的锌粉涂料和富锌涂层体系的报道.本文主要评述了基于溶剂或水基配方的现代锌片涂料,并讨论了添加剂和涂料组分对材料性能的影响.     

Measuring flake orientation for metallic coatings

Metallic and pearlescent coatings, very popular in automotive applications, contain flake shaped pigments. The orientation distribution of these flakes inside the effect coatings determines to a large extend the color and visual appearance of the coating. Unfortunately the measurement of flake orientation distributions is far from straightforward. The two main current techniques use analysis with light microscopy on cross cuts, and confocal microscopy.We used both techniques on a large set of samples. A set of 117 metallic coatings were analyzed, where we varied the concentration of metallic pigment, the concentration of so-called disorienting agent and the type and size of metallic pigment. Trends that for a long time have been assumed to be true were now unambiguously proven true, and can now be stated in a quantitative manner. For example, large flakes generally show better orientation than small flakes. For waterborne cornflake pigments, we measured an orientation width of 19.4° for flakes with a median diameter of 16 μm, and only 7.2° for flakes with a median diameter of 35 μm. Surprisingly we found only a small effect on flake orientation when disorienting agent was added to a color formula.     

Visual appearance and scratch resistance of high performance thermoset and thermoplastic powder coatings

A comparative evaluation of electrostatic spray and ‘hot dipping’ fluidized bed to deposit two different organic paints belonging to the class of thermoplastic (PPA571, an alloy of acid modified polyolefins) and thermoset (TGIC-free transparent pigmented bronze polyester) powders was performed. Visual appearance of the investigated coatings was evaluated by colour, gloss and coating thickness measurements as well as by the determination of the surface morphologies. Micro-mechanical performance of the coatings was assessed by progressive load scratch tests.     

Thermosetting powder coatings: Finish appearance and durability at cure window corner points

This project investigated the finish quality of automotive powder coatings in terms of appearance, adhesion and chip resistance. Two powder basecoats (red and black), of three particle sizes, and a colorkey primer (red) were studied in relation to the process temperature and time pairs based on the cure window provided by the paint manufacturer. The appearance was quantified using the contrast values of the wave-scan structure spectrum elements (Wa, Wb, Wc, Wd, and We). Gravel and scratch tests were used to quantify adhesion and chip resistance properties.It was found that long-waves (Wc, Wd and We) were less affected by the curing time and temperature variation. The contrast values of short-waves (Wa and Wb) increased with increasing process temperature and time. The most dramatic increase was observed at high process time and temperature. High process temperatures (193 °C) resulted in good long-wave coverage. Small contrast values of the long-waves were obtained for all cure conditions, for both red and black basecoats. The results for short-waves were not as consistent. This work suggests that powder basecoats and colorkey primers can yield appearance qualities comparable to water-borne counterparts.     

UV固化粉末涂料

叙述了紫外固化粉末涂料的机理、生产、施工及光引发剂的选择，并给出Uvecoat系列树脂的应用范围。     

抗菌粉末涂料

以无机氧化物包覆银离子抗菌剂制备的抗菌粉末涂料抑菌效果好、时效长。介绍抗菌添加剂 ,抗菌粉末涂料的涂膜性能及抗菌效果。     

Electrochemical investigations into polypyrrole/aluminum flake pigmented coatings

In this study polypyrrole was synthesized in the presence of aluminum flake to produce polypyrrole/aluminum flake hybrids. The resulting flakes were incorporated into a standard epoxy coating at relatively high pigment volume concentrations with the end goal of producing a conducting film capable of providing corrosion inhibition to an aluminum alloy. To further investigate the coatings, electrochemical impedance spectroscopy (EIS) was used to characterize the effects of the pigment volume concentration (PVC) on the impedances of the coatings. Additionally, the nature of the polypyrrole, chemical composition, and surface morphology of the hybrid were characterized by a density test and scanning electron microscopy (SEM).     

粉末涂料用混合机

主要讨论了在粉末涂料热熔挤出之前的混合,对混合、混合机器、混合机器的选择做了详细的说明,特别对现在比较热门的邦定工艺做了简单的介绍。     

A mechanistic study of the effect of pigment loading on the appearance of powder coatings: The effect of surface topography on the optical properties of powder coatings: Modelling and experimental results

Gloss is a critical property for many powder coating applications and is related to the amount of light reflected by the coating layer on a substrate. Gloss of powder coatings can, depending on the composition, vary from excellent to matt. It is well known in the powder coatings industry that increasing loadings of pigment, especially TiO₂, causes a detrimental loss of gloss. In order to understand the cause of this phenomenon two questions have to be addressed: firstly, what is the relation between the optical properties and the surface topography of the powder coating and, secondly, how do the powder coating composition and curing conditions affect the surface topography? In order to answer the first question, the typical features of the surface of a cured powder coating have been studied in detail. Using a white light interferometer, it has been shown that the surface topography consists of both short wave and long wave patterns. Each of these patterns could be described by using two statistical parameters only, the root mean square height of the roughness and its correlation length. The effect of both the short and long wave roughness on the gloss has been simulated with a single wave pattern model, based on an approximation of the Kirchoff scattering theory [9]. These simulations illustrated that neither the short nor the long wave roughness on itself determines the optical properties. In order to quantify the combined effect of the long and short wave surface features a two-scale modelling approach was followed. The predictions of this model were in good agreement with experimental gloss data of coatings containing different amounts and types of pigments.