Paint Coating Specification: Adopted Courtesy of: http://coatings.specialchem.com.cn/tc/powdercoatings/index.aspx?id=resin
1. 环氧粉末涂料 2. 环氧—聚酯复合粉末涂料 3. 聚氨酯—聚酯粉末涂料
4. 聚酯 TGIC 粉末涂料 5. 丙烯酸系列粉末涂料 6. 聚氯乙烯粉末涂料 7. 聚烯烃粉末涂料 8. 尼龙粉末涂料 9. 聚酯粉末涂料 10. 聚偏二氟乙烯
粉末涂料配方中树脂组分对粉末涂料的施工工艺及涂层的最终性能起决定性的影响。以下为最常 用的热固性 Thermosets 及热塑性粉末涂料 thermoplastics 的性能及应用领域一览（点击每一种 树脂可浏览相关介绍）。
环氧树脂 环氧―聚酯复合物 聚氨酯―聚酯 聚酯 TGIC 丙烯酸系列
聚氯乙烯 聚烯烃 尼龙 聚酯 聚偏二氟乙烯
本表并未包括其它已商业化应用、但应用范围不及本表所列树脂广泛的粉末涂料树脂。 粉末涂料主要分为两类：热塑性粉末涂料和热固性粉末涂料。加热后，热塑性粉末涂料将熔融并 发生流动，一旦冷却它们就能形成固态的涂层。受热和冷却前后，它们的化学组成仍保持不变。热 固性粉末涂料在加热后也发生熔融，然而，在流动并形成连续涂膜后，进一步受热将使它们发生交 联。最终的涂层与施工前粉末的化学结构已然不同。表 3 和表 4 分别是热固性粉末涂料和热塑性粉 末涂料的相关性质一览。
表 3 热固性粉末涂料树脂性能比较
环氧 HB-7H 60-160 3-100+ 任意色彩、透 明、 纹理 盐雾试验 冷凝湿度 固化范围* 1000 h 1000 h 232℃3min ― 121℃25min
环氧复合物 HB-2H 60-160 10-100+ 任意色彩、透 明、纹理 1000 hrs min 1000 h min 204℃10min ― 149℃25min
聚氨酯 ―聚酯 HB-4H 60-160 15-95 任意色彩、透 明、纹理 1000 hrs 1000 h 204℃10min ― 149℃25min
TGIC 聚酯 HB-4H 60-160 20-90 任意色彩、透 明、纹理 1000 hrs min 1000 h min 204℃10min ― 149℃C25min
丙烯酸系列 H-4H 40-100 10-90 任意色彩、透 明、纹理 1000 hrs min 1000 h min 204℃10min ― 149℃25min
硬 度 (铅笔) 抗冲击性 (英寸-磅) 光泽度 (60 度.米) 色 彩
* 涂膜厚度为 2 密耳（50 m），于熔融温度时计时。
表 4 热塑性粉末涂料的物理性能及涂层性能
是否要求配套底漆 熔点 ℃ 典型预加热温度/后加热温度 ℃
是 130-150 284 / 230
是 186 310 / 250
否 160-170 300 / 250
附着力 表面 光泽度, 60 度 铅笔硬度 抗冲击性 耐盐雾性
优秀 平滑 40-90 HB-2H 优秀 良好
优秀 平滑 20-95 B 优秀 优秀
优秀 轻微剥离 60-95 B-H 良好 良好
耐气候性 耐湿性 耐酸性 耐碱性 耐溶剂性
良好 优秀 优秀 优秀 较好
良好 优秀 较好 优秀 优秀
优秀 良好 良好 良好 较好
一旦固化，热固性涂层将对热稳定。与热塑性涂层不一样，即使重新加热热固性涂层也不会回到熔 融状态。热固性涂层也较热塑性涂层坚韧，对基材有更好的附着力，其耐溶剂性和耐化学品性也优 于热塑性涂层。在所有粉末涂料中，热固性粉末涂料约占了 95%的比例。 典型地热塑性粉末涂料都是高分子量材料，一般要求较高的温度来熔融和流动。热塑性粉末涂层 的最主要的优点在于它们能形成更平滑的饰面，施工中耗能较少。它们一般采用流化床工艺来施工。 涂饰部件需要预加热和后加热。大部分的热塑性粉末涂料都存在边缘附着效应，因此热塑性粉末涂 料在施工中，基材需预加热，有时还需配套底漆使用。
聚酯 TGIC 粉末涂料 polyestertgic
聚酯―异氰脲酸三缩水甘油酯（TGIC）粉末涂料 , (triglycidyl isocyanurate) stand for TGIC 聚酯―异氰脲酸三缩水甘油酯（TGIC）粉末涂料是两种已经商业化的聚酯粉末涂料之 一（另外一种是聚氨酯―聚酯粉末涂料）。在这种粉末涂料中，添加了低分子量的缩水甘 油基或环氧基官能团固化剂用以与聚酯起作用。这样，聚酯在粉末涂料中占了很高的比 例，因而聚酯―异氰脲酸三缩水甘油酯粉末涂料具有氨基甲酸酯固化的聚酯粉末涂料不可 比拟的耐候性和抗腐蚀性。然而，聚酯―异氰脲酸三缩水甘油酯粉末涂料的耐溶剂性和耐 化学品性不如聚氨酯―聚酯粉末涂料。 TGIC 粉末涂料具有良好的附着性、抗腐蚀性及户外耐久性。代表性地，它们的固化温 度低于聚氨酯―聚酯粉末涂料，固化周期也较聚氨酯―聚酯粉末涂料短。另外，TGIC 粉 末涂层厚而坚韧，并具有良好的边缘覆盖率。 聚酯―异氰脲酸三缩水甘油酯（TGIC）粉末涂料典型应用于尖锐边缘或转角存在的场
polyester-epoxy (known as hybrid)
环氧―聚酯复合粉末涂料是由环氧树脂和聚酯树脂配制而成的，有着许多与环氧粉末涂料 相同的特性。除了在复合涂料中聚酯的百分含量特别高（一般超过一半）外，环氧―聚酯 复合粉末涂料可以视为是环氧涂料家族的一个部分。 环氧―聚酯复合粉末涂料的性质与它们相对等的环氧树脂涂料的性质很相似。一般来说， 环氧―聚酯复合粉末涂层坚硬、柔韧，与单纯的环氧粉末涂料相比，在价格上具有一定的 竞争优势。两种树脂的复合还改善了环氧涂料的耐气候性。但是，环氧―聚酯复合粉末涂 料与单纯的环氧粉末涂料的粉化速度几乎一样。然而，在起始粉化之后，环氧―聚酯复合 粉末涂料的进一步粉化会较环氧粉末涂料变缓。一些环氧―聚酯复合粉末涂料的耐化学品 及耐溶剂性较单纯的环氧粉末涂料有所降低。环氧―聚酯复合粉末涂料多用于与环氧粉末 涂料相同的场合。
聚氨酯―聚酯粉末涂料是两种已经商业化的聚酯粉末涂料之一（另外一种是聚 酯―异氰脲酸三缩水甘油酯（TGIC）粉末涂料）。聚氨酯固化的聚酯粉末涂料是 聚氨酯―聚酯粉末涂料的主要型号，已经使用数年。这种粉末涂料的户外性能在化 学上能与应用于飞机、公共汽车、货车等场合的聚氨酯涂料相媲美。另外，聚氨 酯―聚酯粉末涂层坚韧、外观良好，并具有优异的耐气候性。 在聚氨酯―聚酯体系中，采用 e-己内酰胺作为封端剂来控制交联已经是很常用 的方法了。要开始交联，物料温度须超过封端剂的临界温度。e-己内酰胺的解封端 温度约为 182℃。
就涂层的外观而言，聚氨酯―聚酯粉末涂层可以说是那些高质量液体涂料的真 正意义上的竞争者。它们的户外应用如：院落家具、汽车轮胎和配件、除草机以及 其他许多要求高质量饰面的制品。
当要求涂层坚硬、电绝缘且能在较宽的温度范围内均能起保护作用时，往往使用环氧涂层。 随所选用的特殊环氧树脂的不同，环氧涂层的使用温度可达 150° 甚至更高。10 密耳 C （250m）的环氧粉末涂层厚度的介电强度可达 1200 伏/密耳。这样，环氧粉末涂层不但 可以起到良好的保护作用，也具有突出的电绝缘功能。环氧粉末涂层对大多数溶剂、弱酸、 弱碱化学稳定，涂层坚韧，具有优异的防腐性。另外，环氧粉末涂层对金属基质具有良好 的附着力因而一般情况下不需要底漆。 环氧粉末涂层的主要应用限制在于当涂层的厚度超过一定值后存在脆化倾向， 在紫外 光辐射下，涂层将粉化。正因为这些原因，环氧粉末涂层很少用于户外场合。 环氧粉末涂层经常用于装饰场合。不同的配方可提供它们多种不同的颜色、光泽和纹理。 典型应用如金属办公家具、货架、汽车内部零件及玩具。
丙烯酸类粉末涂料具有优异的户外耐久性。常规丙烯酸系列粉末涂料包括聚氨酯―丙烯酸系粉末涂 料、丙烯酸系复合粉末涂料、甲基丙烯酸缩水甘油酯（GMA）丙烯酸树脂粉末涂料。 聚氨酯―丙烯酸系粉末涂料的固化温度为 182° C，形成的薄膜涂层坚硬、外观美丽，具有良好的 耐化学品性，但其抗划伤性、抗冲击性能较差。与聚氨酯―丙烯酸系粉末涂料相比，GMA 丙烯酸 树脂粉末涂料所要求的固化时间较短、固化温度较低。GMA 丙烯酸树脂涂层具有优良的耐气候性， 而且，这种涂料能在铜或铬的表面形成优异的透明涂层。与聚氨酯―丙烯酸系涂层类似，GMA 丙 烯酸树脂涂层的抗抗划伤性也受到一定的限制。丙烯酸系复合粉末涂料是丙烯酸树脂与环氧粘合剂 的复合物，一般来说，这种复合涂料稍优于聚酯―环氧复合涂料，但它们的仍然不能应用于户外场 合。与其他丙烯酸系粉末涂料相比，丙烯酸系复合涂层具有更好的机械力学性能。
聚氯乙烯（PVC）粉末涂料因其优秀的冲击强度、回弹性、抗盐雾性及耐气候性而获得应用。PVC 粉末涂层还有些软而柔韧、有光泽。 PVC 粉末涂料具有良好的耐化学品及耐水性，通过调整其配方可应用于美国食品及药物管理局 （FDA）批准的特殊领域如冷冻食品架及洗碗机筒。PVC 涂层的普通用途包括电绝缘场合。PVC 粉末涂料也可用于金属防护网、户外家具及相关场合的涂饰。 为了获得最佳的附着性能，PVC 粉末涂料在施工时一般需配套特殊底漆。目前，两种聚氯乙烯 粉末涂料（干混合料和熔融混合料）已获得使用。干混合的 PVC 粉末涂料价格较熔融混合的 PVC 粉末涂料便宜，但其性能也不如后者。
聚乙烯和聚丙烯粉末涂层与聚乙烯和聚丙烯塑料很相似，柔软而有蜡感。聚乙烯和聚丙烯粉末涂料 获得应用主要是基于它们成本低、操作简单。然而，它们某些独特的性能也颇引人注目，因而在很 多方面也获得了应用。除了与其它热塑性塑料一样具有一定的韧性外，它们的吸水性较低，并具有 优异的化学稳定性和良好的电绝缘性能。对很多化学物质和洗涤剂而言，聚乙烯和聚丙烯粉末涂层 都具有抵抗力和耐久性，然而，某些溶剂能使得它们迅速破坏。 由于涂层表面易清洁，聚烯烃粉末涂料常用于实验室设备。它们也用于食品加工设备和汽车工业 如汽车电池固定。
尼龙粉末涂料一般是基于尼龙 11 的。尼龙 6/10 有些时候也使用，但其成本高于尼龙 11。尼龙粉 末涂层坚韧，有着优异的耐磨损性、耐磨耗性和抗冲击性，其摩擦系数也低。另外，尼龙粉末涂层 还具有良好的耐化学品和耐溶剂性，其涂膜表面一般非常光滑。一般来说，为了获得较高的应用性 能，尼龙粉末涂料在施工过程中需要配套使用底漆以提高其附着力。
适宜配方的尼龙粉末涂料可用于食品接触制品的涂饰。尼龙粉末涂料还能在棚架材料的表面形成 优异的涂层。另外，由于尼龙粉末涂层的低摩擦系数和良好的润滑性，它们非常广泛地施用于轴承 表面以防止轴承因机械磨损而破坏。一些尼龙粉末涂料还用于户外场合如轻质家具或座椅。在海运 业中，尼龙粉末涂料也获得了广泛应用，如用于包覆各种零配件、螺钉螺栓及其它硬件等。
热塑性聚酯粉末涂料的附着性能较常规涂料有了很大的改观，它们在使用过程中无需底漆，具有良 好的抗紫外线辐射和耐候性。与尼龙类材料相比，聚酯粉末涂料在施工过程中稍微显得有些困难。 另外，聚酯粉末涂料的耐磨损性和耐溶剂性能较差。 由于较好的耐久性、良好的耐气候性和抗腐蚀性，聚酯粉末涂层常用于户外金属家具。
Introduction to Powder Coatings
Adopted courtesy of : http://oem.sherwinwilliams.com/us/eng/resources/guides/system/powder/performancecomplian/
Performance and Compliance
Powder is a smart alternative in this age of stiff competition and an ever increasing number of environmental mandates. If you believe that all powder coatings are the same, consider the options and service available only when you choose Sherwin-Williams line of POWDURA coatings. From knowledgeable service reps to troubleshooting line technicians, you get unparalleled support from Sherwin-Williams. Combine this with a wide range of high quality, high performance powder coating technologies, in both
standard and custom colors, and receiving product fast from nationwide distribution centers, and it's easy to see that not all powders are created equal. About Powdura Powder Coating Systems Powdura Powder coatings are the right choice for today's advanced engineered products. Environmentally-friendly, production efficient, and capable of satisfying the most exacting performance and application requirements, powders overcome many of the challenges faced by OEM and job shop finishers. Sherwin-Williams is your complete source for environmentally-compliant product finishes -both liquid and powders. Since its founding by Henry Sherwin and Edward Williams in 1866, the company has continually pushed the envelope of coatings technology. It has also led the industry in service and technical support. Building on this tradition, Sherwin-Williams developed POWDURA powder coating systems for industrial product finishing. Proven Performance Because no two finishing operations are exactly the same, we offer a variety of powder formulations that are developed to address your special finishing needs. All the technologies are available in a wide range of colors and finishes. In today's competitive marketplace, it's not enough to create a flawless finish. The powder coating selected must also be production efficient and exhibit the performance characteristics to withstand the harshest conditions within the product's service environment. POWDURA coatings build on the strength of our finishing line. Whether it's low-cure or thin-film, out-gas-free or E-cap-free, Sherwin-Williams has the right technologies to ensure your finishing line runs smoothly and at peak efficiency-allowing you to finish ahead of the rest.
Powder Types & Characteristics
Epoxy For a finish with optimum film properties, POWDURA Epoxies are the answer. Hard, impact resistant and solvent resistant, these coatings provide long-term protection to products designed for interior service environments. Applicators also benefit from flexible cure schedules, and the availability of these epoxies in both standard and lowcure formulations. Typical applications include industrial equipment, automotive underbody components, furniture, and appliances. Polyester Available in both TGIC and TGIC-Free formulas, POWDURA Polyester coatings form attractive finishes that leave lasting impressions. Excellent color and gloss retention, good overbake stability, and superior mechanical properties make these versatile finishes the right choice for a wide range of applications, including electronic cabinetry, case goods, transformer housings, and furniture. Hybrid When the mechanical film properties of an epoxy and the overbake stability of polyesters
are needed, POWDURA Hybrid powders are the perfect choice. These finishes display exceptional transfer efficiency, permitting more powder to penetrate recesses, corners, and multidimensional substrates. Available in thin-film formulations, POWDURA Hybrid coatings are commonly specified for finishing office furniture, automotive components, shelving, and exercise equipment. Polyester Urethane POWDURA Polyester Urethanes deliver a high definition finish with excellent resistance to weathering and ultraviolet light exposure. Recommended for products used in interior or exterior environments, the coatings display good color and gloss stability, and are available in anti-gassing and E-Cap Free formulas. For products such as lawn/garden equipment, outdoor furniture, electronic cabinetry, and automotive components, POWDURAT Urethanes provide the extra needed durability against prolonged weathering. See next section for a comparison chart.
Adopted Courtesy of
Powder coating is a type of coating that is applied as a free-flowing, dry powder. The main difference between a conventional liquid paint and a powder coating is that the powder coating does not require a solvent to keep the binder and filler parts in a liquid suspension form. The coating is typically applied electrostatically and is then cured under heat to allow it to flow and form a "skin." The powder may be a thermoplastic or a thermoset polymer. It is usually used to create a hard finish that is tougher than conventional paint. Powder coating is mainly used for coating of metals, such as "whiteware", aluminium extrusions, and automobile and bicycle parts. Newer technologies allow other materials, such as MDF (medium-density fibreboard), to be powder coated using different methods.
Advantages and disadvantages of powder coating
There are several advantages of powder coating over conventional liquid coatings:
1. Powder coatings emit zero or near zero volatile organic compounds (VOC). 2. Powder coatings can produce much thicker coatings than conventional liquid coatings without running or sagging. 3. Powder coating overspray can be recycled and thus it is possible to achieve nearly 100% use of the coating. 4. Powder coating production lines produce less hazardous waste than conventional liquid coatings. 5. Capital equipment and operating costs for a powder line are generally less than for conventional liquid lines. 6. Powder coated items generally have fewer appearance differences between horizontally coated surfaces and vertically coated surfaces than liquid coated items. 7. A wide range of specialty effects is easily accomplished which would be impossible to achieve with other coating processes.
While powder coatings have many advantages over other coating processes, there are limitations to the technology. While it is relatively easy to apply thick coatings which
have smooth, texture-free surfaces, it is not as easy to apply smooth thin films. As the film thickness is reduced, the film becomes more and more orange peeled in texture due to the particle size and TG (glass transition temperature) of the powder. Also powder coatings will break down when exposed to uv rays between 5 to 10 years. For optimum material handling and ease of application, most powder coatings have a particle size in the range of 30 to 50 μm and a TG > 40°C. For such powder coatings, film build-ups of greater than 50 μm may be required to obtain an acceptably smooth film. The surface texture which is considered desirable or acceptable depends on the end product. Many manufacturers actually prefer to have a certain degree of orange peel since it helps to hide metal defects that have occurred during manufacture, and the resulting coating is less prone to show fingerprints. There are very specialized operations where powder coatings of less than 30 micrometres or with a TG < 40° are used in order to produce smooth thin films. One variation of the C dry powder coating process, the Powder Slurry process, combines the advantages of powder coatings and liquid coatings by dispersing very fine powders of 1–5 micrometre particle size into water, which then allows very smooth, low film thickness coatings to be produced. Powder coatings have a major advantage in that the overspray can be recycled. However, if multiple colors are being sprayed in a single spray booth, this may limit the ability to recycle the overspray
Types of powder coatings
There are two main categories of powder coatings: Thermosets and thermoplastics. The thermosetting variety incorporates a cross-linker into the formulation. When the powder is baked, it reacts with other chemical groups in the powder polymer and increases the molecular weight and improves the performance properties. The thermoplastic variety does not undergo any additional reactions during the baking process, but rather only flows out into the final coating. The most common polymers used are polyester, polyurethane, polyester-epoxy (known as hybrid), straight epoxy (Fusion bonded epoxy) and acrylics. Production:
1. The polymer granules are mixed with hardener, pigments and other powder ingredients in a mixer 2. The mixture is heated in an extruder 3. The extruded mixture is rolled flat, cooled and broken into small chips 4. The chips are milled to make a fine powder 5.
The powder coating process
The powder coating process involves three basic steps: 1. Part preparation or the Pre treatment 2. The powder application 3. Curing The powder coating process involves three basic steps:
1. Part preparation or the Pre treatment 2. The powder application 3. Curing
Part Preparation Processes & Equipment Removal of oil, soil, lubrication greases, metal oxides, welding scales etc. is essential prior to the powder coating process. It can be done by a variety of chemical and mechanical methods. The selection of the method depends on the size and the material of the part to be powder coated, the type of soil to be removed and the performance requirement of the finished product. Chemical pre-treatments involve the use of phosphates or chromates in submersion or spray application. These often occur in multiple stages and consist of degreasing, etching, de-smutting, various rinses and the final phosphating or chromating of the substrate. The pre-treatment process both cleans and improves bonding of the powder to the metal. Recent additional processes have been developed that avoid the use of chromates, as these can be toxic to the environment. Titanium Zirconium and Silanes offer similar performance against corrosion and adhesion of the powder. Another method of preparing the surface prior to coating is known as abrasive blasting or Sandblasting and shot blasting. Blast media and blasting abrasives are used to provide surface texturing and preparation, etching, finishing, and degreasing for products made of wood, plastic, or glass. The most important properties to consider are chemical composition and density; particle shape and size; and impact resistance. Silicon carbide grit blast media is brittle, sharp, and suitable for grinding metals and lowtensile strength, non-metallic materials. Plastic media blast equipment uses plastic abrasives that are sensitive to substrates such as aluminum, but still suitable for decoating and surface finishing. Sand blast media uses high-purity crystals that have lowmetal content. Glass bead blast media contains glass beads of various sizes. Cast steel shot or steel grit is used to clean and prepare the surface before coating. Shot blasting recycles the media and is environmentally friendly. This method of preparation is highly efficient on steel parts such as I-beams, angles, pipes, tubes and large fabricated pieces.
Different powder coating applications can require alternative methods of preparation such as abrasive blasting prior to coating. The online consumer market typically offers media blasting services coupled with their coating services at additional costs. Powder Application Processes The most common way of applying the powder coating to metal objects is to spray the powder using an electrostatic gun, or Corona gun. The gun imparts a positive electric charge on the powder, which is then sprayed towards the grounded object by mechanical or compressed air spraying and then accelerated toward the workpiece by the powerful electrostatic charge. There are a wide variety of spray nozzles available for use in electrostatic coating. The type of nozzle used will depend on the shape of the workpiece to be painted and the consistency of the paint. The object is then heated, and the powder melts into a uniform film, and is then cooled to form a hard coating. It is also common to heat the metal first and spray the powder onto the hot substrate. Preheating can help to achieve a more uniform finish but can also create other problems, such as runs caused by excess powder. See the article "Fusion Bonded Epoxy Coatings" Another type of gun is called a Tribo gun, which charges the powder by (triboelectric) friction. In this case, the powder picks up a positive charge while rubbing along the wall of a Teflon tube inside the barrel of the gun. These charged powder particles then adhere to the grounded substrate. Using a Tribo gun requires a different formulation of powder than the more common Corona guns. Tribo guns are not subject to some of the problems associated with Corona guns, however, such as back ionization and the Faraday Cage Effect. Powder can also be applied using specifically adapted electrostatic discs. Another method of applying powder coating, called the Fluidized Bed method, is by heating the substrate and then dipping it into an aerated, powder-filled bed. The powder sticks and melts to the hot object. Further heating is usually required to finish curing the coating. This method is generally used when the desired thickness of coating is to exceed 300 micrometres. This is how most dishwasher racks are coated. Electrostatic Fluidized Bed Coating: Electrostatic fluidized bed application uses the same fluidizing technique and the conventional fluidized bed dip process but with much less powder depth in the bed. An electrostatic charging media is placed inside the bed so that the powder material becomes charged as the fluidizing air lifts it up. Charged particles of powder move upward and form a cloud of charged powder above the fluid bed. When a grounded part is passed through the charged cloud the particles will be attracted to its surface. The parts are not preheated as they are for the conventional fluidized bed dip process. Electrostatic magnetic Brush (EMB) Coating: an innovative coating method for flat materials that applies powder coating with roller technique, enabling relative high speeds and a very accurate layer thickness between 5 and 100 micrometre. The base for this process is conventional copier technology . Currently in use in some high- tech coating
applications and very promising for commercial powder coating on flat substrates ( steel, Aluminium, MDF, paper, board) as well in sheet to sheet and/or roll to roll processes. This process can potentially be integrated in any existing coating line. Curing When a thermoset powder is exposed to elevated temperature, it begins to melt, flows out, and then chemically reacts to form a higher molecular weight polymer in a network-like structure. This cure process, called crosslinking, requires a certain degree of temperature for a certain length of time in order to reach full cure and establish the full film properties for which the material was designed. Normally the powders cure at 200° (390° in 10 C F) minutes. The curing schedule could vary according to the manufacturer's specifications. The application of energy to the product to be cured can be accomplished by convection cure ovens or infrared cure ovens.
Removing Powder Coating
Methylene Chloride is generally effective at removing powder coating, however most other organic solvents (Acetone, thinners, etc.) are completely ineffective. Most recently the suspected human carcinogen Methylene Chloride is being replaced by Benzyl alcohol with great success. Powder coating can also be removed with abrasive blasting. 98% sulfuric acid commercial grade also removes powder coating film. Certain low grade powder coats can be removed with steel wool, though this might be a more labor- intensive process than desired.
What is powder coating? Adopted Courtesy of http://www.finishing.com/Library/chloride.html
Powder coating is by far the youngest of the surface finishing techniques in common use today. It was first used in Australia about 1967. Powder coating is the technique of applying dry paint to a part. The final cured coating is the same as a 2-pack wet paint. In normal wet painting such as house paints, the solids
are in suspension in a liquid carrier, which must evaporate before the solid paint coating is produced. In powder coating, the powdered paint may be applied by either of two techniques.
The item is lowered into a fluidised bed of the powder, which may or may not be electrostatically charged, or The powdered paint is electrostatically charged and sprayed onto the part.
The part is then placed in an oven and the powder particles melt and coalesce to form a continuous film. There are two main types of powder available to the surface finisher:
Thermoplastic powders that will remelt when heated, and Thermosetting powders that will not remelt upon reheating. During the curing process (in the oven) a chemical cross-linking reaction is triggered at the curing temperature and it is this chemical reaction which gives the powder coating many of its desirable properties.
The basis of any good coating is preparation. The vast majority of powder coating failures can be traced to a lack of a suitable preparation. The preparation treatment is different for different materials. In general, for all applications the preparation treatment for aluminium is as follows: Clean Rinse Etch Rinse Chromate Rinse Demin Rinse Or Clean Rinse Etch Rinse Phosphate Rinse Demin Rinse
Oils and greases are removed in weak alkali or neutral detergent solutions and the surface is etched to remove heavy oxides. After rinsing, the aluminium is dipped into a chromate or phosphate solution to form a conversion coating on the aluminium. This film is chemically attached to the aluminium. After rinsing the aluminium is finally rinsed in demineralised water. Some non-chrome, dried in place pretreatment is beginning to come onto the market; currently, these are not recommended for exterior applications.
The conversion coating has two functions:
It presents a surface to the powder which favours adhesion more than the oxides that form very readily on aluminium surfaces, and It reduces the incidence of under film corrosion, which may occur at holidays in the coating.
The use of demineralised water reduces the presence of chemical salts on the aluminium surface. These salts have been found to cause filiform corrosion in humid conditions. For steel the preparation for interior applications may be: Clean Rinse Derust Rinse Iron Phosphate Rinse Acidulated Rinse For exterior applications: Clean Rinse Etch Rinse Grain Refine Zinc Phosphate Rinse Acidulated Rinse The grain refiner is used after acid cleaning of steel surfaces and before zinc phosphating, otherwise the zinc phosphate coatings produced will be very coarse with low adhesion. The powder coating applied to a coarse phosphate will produce rough coatings (a little like "sandpaper") and possess low adhesion. For hot dipped galvanized coatings, which have been stored for more than about 4 hours before powder coating, the following process is necessary for exterior applications. Clean
Rinse Etch Rinse Grain Refiner Rinse Zinc Phosphate Acidulated Rinse The etch is required to remove the zinc corrosion products which begin to form almost immediately the zinc is removed from the galvanizing kettle. The grain refiner ensures a fine phosphate is produced.
How is it done -- electrostatic spray?
The powder is applied with an electrostatic spray gun to a part that is at earth (or ground) potential. Before the powder is sent to the gun it is fluidised:
to separate the individual grains of powder and so improve the electrostatic charge that can be applied to the powder and so that the powder flows more easily to the gun.
Because the powder particles are electrostatically charged, the powder wraps around to the back of the part as it passes by towards the air offtake system. By collecting the powder, which passes by the job, and filtering it, the efficiency of the process can be increased to 95% material usage. The powder will remain attached to the part as long as some of the electrostatic charge remains on the powder. To obtain the final solid, tough, abrasion resistant coating the powder coated items are placed in an oven and heated to temperatures that range from 160 to 210 degrees C (depending on the powder). Under the influence of heat a thermosetting powder goes through 4 stages to full cure. MELT, FLOW, GEL, CURE
The final coating is continuous and will vary from high gloss to flat matt depending on the design of the powder by the supplier.
Powder coating guns
There are at east three types of electrostatic guns in use:
Corona charging guns where electric power is used to generate the electrostatic charge. Corona guns are either internal or external charging. Tribo charging guns where the electrostatic charge is generated by friction between the powder and the gun barrel. "Bell" charging guns where the powder is charged by being "flung" from the perimeter of the "bell"
Not all powder is applied using guns. One system makes use of electrostatic tunnels.
How is colour introduced?
Colour is added to powder coatings during the manufacturing process, ie before the powder reaches the powder coater. There is little that can be done to change the colour consistently, once the powder leaves the manufacturing plant
Why powder coat?
Powder coating produces a high specification coating which is relatively hard, abrasion resistant (depending on the specification) and tough. Thin powder coatings can be bent but this is not recommended for exterior applications. The choice of colours and finishes is almost limitless, if you have the time and money to have the powder produced by the powder manufacturer. Powder coatings can be applied over a wide range of thickness. The new Australian Standard, "AS/NZS 4506 - Thermoset powder coatings", will recommend 25 micron minimum for mild interior applications and up to 60 micron minimum for exterior applications. Care must be exercised when quoting minimum thickness because some powder will not give "coverage" below 60 or even 80 micron. "Coverage" is the ability to cover the colour of the metal with the powder. Some of the white colours require about 75 micron to give full "coverage". One of the orange colours must be applied at 80 micron. Colour matching is quite acceptable batch to batch.
Installations and maintenance
During installations, the powder coating should be protected from damage due to abrasion and materials of construction such as mortar and brick cleaning chemicals. Once installed, maintaining the initial appearance of a powder coating is a simple matter. The soot and grime which builds up on surfaces from time to time contains moisture and salts which will adversely affect the powder coating and must be removed. Powder coatings should be washed down regularly (at least once each 6 months in less severe applications and more often in marine and industrial environments). The coating should be washed down with soapy water -- use a neutral detergent -- and rinsed off with clean water. When powder coated items are installed without damage to the powder coating and they are maintained regularly, they should be relatively permanent. The correctly applied coating, although not metallurgically bonded to the metal will not crack, chip or peel as with conventional paint films.
TYPES OF POWDER COAT
ADOPTED COURTESY OF HTTP://WWW.LINETEC.COM/POWDERCOAT/TYPES_OF_POWDER_COAT.H TML
There are two different types of powder coat - thermoplastic and thermoset. Thermoplasic powders melt and flow when heat is applied but they continue to have the same chemical composition once they cool and solidify. They are generally applied to a surface that has been preheated to a temperature significantly higher than the melting point of the powder. As a thermoplastic powder material is applied to the hot surface it will melt and "fusion bond" to the surface and then "flow out" into a strong, continuous film. As the film cools it develops its physical properties. Nylon powder coating materials are the most commonly used thermoplastic powders. Thermoset powder coatings also melt when exposed to heat, but they then chemically cross-link within themselves or with other reactive components. The cured coating then has a different chemical structure than the basic resin. Thermosetting coatings are heat-stable and, unlike thermoplastic powders, will not soften back to liquid phase when re-heated.
Thermosetting powders are derived from four generic types of resins: epoxy, acrylic, polyester and fluoropolymer. From these resin types, several coating systems are derived. Resins used in thermosetting powders can be ground into fine particles necessary for spray application and a thin film finish. Most of the technological advancements in recent years have been with thermosetting powders.
Thermosetting Powder Coatings
EPOXY resin is a hard, impact resistant interior only formulation. For the most part, epoxy coatings are used as functional coatings for substrate protection where corrosion resistance, impact resistance, and adhesion are essential. The primary limitation of epoxy-based coatings is poor weatherability. Typical applications include industrial equipments, automotive underbody components, metal furniture and appliances. ACRYLIC resins are typically used in the automotive industry as a clear coat on materials. Acrylic creates a smooth clear coat with very good clarity and provides a hard surface that is highly chip-resistant. Acrylic resins are used as additives to promote improved flow and leveling as well as enhanced stain and chemical resistance in polyester hybrid, polyester TGIC, and polyurethane powder coatings. POLYESTER powder coats are the most used of all powder coatings in the U.S. market. Polyester's offer a broad application field and many different chemistries including: Polyester/TGIC (triglycidyl isocyanurate); Polyester/TGIC-free; Super-durable Polyester and Polyester Hybrids. Some Super-durable and Hybrid Polyester resin systems meet the AAMA 2604 specification. FLUOROPOLYMER resins are top of line for exterior weatherability and UV stability in both powder and liquid coatings. Fluoropolymer powder coatings are purposely tailored for the architectural market and offer a long-life durable finish. Fluoropolymer powder coat resin systems can be formulated to meet the requirements of the high performance AAMA 2605 specification.
Characteristics including color and gloss are utilizes to determine how well a coating will withstand harsh environmental conditions. Coatings are tested by exposing test samples to the heat and humidity conditions of South Florida. The following paint types have been been proven to meet the corresponding architectural AAMA specification.
POWDER COAT OVERVIEW
Powder coating is a dry film process, using finely ground particles of pigment and resin which are electrostatically charged and sprayed onto electrically grounded parts to be coated. The charged powder particles adhere to the parts and are held there until melted and fused into a uniformly flowing coating in a cure oven. Before coating, the parts must be pretreated similar to liquid coated parts.
Powder coat such as Akzo Nobel's Interpon D3000 that contain 70% of fluorocarbon resin in polymer matrix and PPG's Duranar powder coat that combines proprietary resin and pigment technologies with 70% of the resin system being fluoropolymer base resins offer good choices for high-performance AAMA2605 powder coat. The primary component of powder coat is referred to as the resin. The type of powder coat system comes from the resin system. The powder coating formulation is much like a liquid coating except that most of the components are in solid, melt processable form.
The exact composition of a particular powder coating is often complex and proprietary. In general most powder paints contain resins, pigments, fillers and additives.
Resin System: Resins are the key component of powder coatings. The range of powder coat resins used have increased to meet the demands the architectural market sector. Resin systems include: Kynar (PVDF), Polyester, Super Durable Polyesters, Urethane, Epoxy, Acrylic, and Nylon. Pigment: Pigments are the material added to the paint to give it color or to enhance certain physical properties of the coating. The selection of pigments is done on the basis of physical needs, durability, gloss, color fastness and chemical exposure. Pigments are both naturally occurring as well as synthetic. Typically solid particulate materials such as titanium dioxide or carbon black. Fillers: Used to reduce cost of the coating formulation and to improve specific properties such as flow, surface texture, lubricity, etc. Common fillers include barytes, calcite, mica, talc, whiting and wollastonite.
The raw powder coatings, composed of resin, pigment, curing agent and fillers are mixed dry and then melt mixed and extruded. once cooled, the mixture is chipped and ground into finely divided particles. The chips are ground to a very specific particle size distribution depending on the application.
The particle size is important to the performance and appearance of the coating. The size of the powder particle can have an influence on the behavior of the material in the painting process and the final film characteristics.
What are the AAMA specifications for Powder Coat?
Powder coatings are held to the same AAMA performance comparisons as liquid paints are. Powder coatings formulated with standard polyesters can most often pass the AAMA 2603 specification. Comparatively, powder coatings properly formulated with super-durable polyesters can pass AAMA 2604 specification. Powder coatings manufactured from fluorocarbon polymer resins exhibit the greatest exterior durability and will meet the requirements of AAMA 2605.
Architects and building owners should determine which performance specification is required, along with the finish color. In order to ensure the powder coat performance expected for a given application, one of three AAMA specifications should be referenced: AAMA 2603, 2604, and 2605. These three specifications apply to progressively stronger levels as indicated by South Florida outdoor exposure and laboratory accelerated testing results as shown below.
AAMA Specifications for Paint and Architectural Powder Coat Specification 2603 2604 2605 South Florida Weathering: 10 yrs: Fade = 5 Delta Color retention 1 year: "slight" fade 5 yrs: Fade = 5 Delta E E Chalk 1 year: "slight" chalk 5 yrs: Chalk = 8 10 yrs: Chalk = 8 resistance Gloss retention No specification 5 yrs: 30% retention 10 yrs: 50% retention Erosion No specification 5 yrs: 10% loss 10 yrs: 10% loss resistance Dry film thickness 0.8 mils minimum 1.2 mils minimum 1.2 mils minimum
Pretreatment Chrome or Chrome Free Chrome or Chrome Free Chrome or Chrome Free System: * * * Accelerated Testing: Salt Spray Humidity
1,500 hours 1,500 hours
3,000 hours 3,000 hours
4,000 hours 4,000 hours
Linetec is 100% compliant of all AAMA specifications. AAMA's Certification Program Verified Components List is a complete list of window and door component manufacturers who have submitted samples for testing and those samples were found to be in full compliance with the applicable specification. For detailed spec information or to purchase AAMA specifications visit www.aamanet.org. All AAMA documents may be ordered through the Public Store
PERFORMANCE OF POWDER COAT FINISHES
TGIC-POLYSTER Property. Adopted Courtesy of: http://www.china-powdercoatings.com/conteat08b.htm
Polyester ( TGIC / Primid )
Hybrid ( Epoxy / Polyester )
粉末涂料分类 (依烘烤后的变化可分为热固性粉末涂料和热塑性粉末涂料) 根据树脂分类： 纯环氧 pure epoxy 混合型 hybrid 纯聚酯 pure polyester (聚酯/TGIC, 聚酯/TGIC FREE) 聚氨酯 polyurethane 丙烯酸 acrylic 根据涂膜状态分类 亮光型(60 度角) G>85% 半平光型(60 度角) G=10～85% 平光型(60 度角) G<10 美术型 根据用途分类 装饰用粉末涂料 绝缘用粉末涂料 重防腐用粉末涂料 建筑用粉末涂料 粉末涂料的特性及应用 产品项目 1.高光泽 2.平光及半平光泽 3.砂纹、锤纹及各式样花纹效 果 4.混色效果 5.金属粉涂料 6.磨擦枪专用 1.高光泽 2.平光及半平光泽 3.砂纹、锤纹及各式样花纹效 果 4.混色效果 5.金属粉涂料 6.磨擦枪专用 产品特性 1.优异的耐化学品性和电器绝缘 性 2.防腐蚀能力佳 3.高硬度 4.优异的物理机械性 5.良好的耐溶剂性 产品用途 1.室内金属家具用品 2.汽车零部件 3.玩具 4.钢筋、输油输水管道 5.室内电器 6.电子绝缘零件 1.室内金属家具及制品 2.仓储陈列架 3.室内电器用品 4.办公家具 5.汽车零部件 6.灯饰 7.电脑外壳 8.玩具 9.工业机械部件 1.户外金属制品 2.园艺工具 3.铝型门窗 4.高速公路护栏 5.室外家具及电器 6.铜制门 7.沙滩椅 8.配电盘、电器箱 1.户外金属制品 2.园艺工具
环 氧 型
混 合 型
1.亮丽平滑的涂膜 2.优异的机械物理性 3.良好的耐黄变性 4.优良的耐腐蚀性能
聚 酯 型
1.高光泽 2.平光及半平光泽 3.砂纹、锤纹及各式样花纹效 果 4.混色效果 5.金属粉涂料 6.磨擦枪专用 1.高光泽 2.平光及半平光泽
1.极佳的耐候性 2.亮丽平滑的涂膜 3.边缘包覆性好 4.低温烘烤 5.适合薄涂
3.砂纹、锤纹及各式样花纹效 果 4.混色效果 5.金属粉涂料 6.磨擦枪专用
3.铝型门窗 4.高速公路护栏 5.室外家具及电器 6.铜制门 7.配电盘、电器箱
1． 树脂： 环氧树脂 聚酯树脂（端羧基聚脂树脂） 聚氨脂树脂（端羟基聚酯树脂） 丙烯酸树脂 2． 颜填料： 以微细粉末状态分散于介质中，对物体形成遮盖着色或填 充作用的物均可称为颜料，前者为着色颜料，后者为体质 颜料或称为填料。 颜料的分类：无机颜料、有机颜料、金属颜料、荧光颜 料、珠光颜料、体质颜料等。 无机颜料 氧化铁系列 氧化铬系列 硫化物系列：铬酸盐、钼 酸盐、铝酸盐、钛酸盐系列 群青 碳黑 二氧化钛 金属颜料 金粉 银粉 体质颜料 硫酸钡 碳酸钙 高岭土 百碳黑 方解石 石英粉 硅灰石 有机颜料 酞青系列 还原颜料 偶氮颜料 二恶嗪颜料 喹吖啶颜料 异吲哚啉酮系颜料
3． 助剂： 促进剂、流平剂、消光剂、光稳定剂、美术型助剂、增塑 剂、消泡剂、温联剂、边缘覆盖剂、防结块剂等。
粉末涂料的优点 自从粉末涂料涂装技术进入涂装业后，所占有的市场比例逐年持续增长，而之所以能够持续增长，是因为 具有以下优异性能。 1． 降低环境污染 随着环保法令对在大气层中有机挥发物(VOC)含量的规定越来越严格，涂装业界寻求各种办法来改善涂装 技术以降低对环境的污染。经过长期的实验与测试后，终于发现“粉末涂装”是目前能够达到的最理想的涂装 技术。 粉末涂料不使用有机溶剂、水等挥发性溶剂，因此粉末涂料为无机溶剂型涂料，大大减少了因溶剂而产生 的安全隐患，如因含有有机溶剂而引起的操作人员有机溶剂中毒事件；或因为有机溶剂带来的火灾等。从上世 纪五、六十年代粉末涂料面世至今，还没有发生过因粉末涂料而引起的重大安全事故。 粉末涂料是百分之百的固体份粉末状的涂料，完全可采用全自动喷涂。过量或超喷的粉末涂料，可经由回 收系统装置而达到回收再利用的目的，因此粉末涂料几乎可达百分之百的使用率，使得涂装业界降低废弃物的 处理，同时使环境污染的程度降低至最低。 2. 节约能源 纵观粉末涂料与液体涂料的能源成本。液体涂料因为含有有机挥发物，造成挥发物的挥发至大气层中；而 粉末涂料则不会有此种的浪费，大大降低了能源的使用 静电涂装机的吐出量大而且一次喷涂即可得厚膜，不必重复喷涂，也不必打底漆，在相同膜厚的情况下， 使用粉末涂料的涂装作业比较迅速，可节约时间成本。 涂装设备中不需要静止时间（Setting Time），可节省设备空间。另外，粉末涂装的烘烤时间也少于液体 涂装，如此，可大大降低燃料能源，缩短涂装作业线，提高产能，促进整体生产的效率化。 3. 优异的涂膜性能 只要直接将粉末涂料喷涂于经过合适前处理的铁材或铝材等，经烘烤即可得到性能优异的涂膜表面，如涂 膜的持久性，其中包括：耐磨擦性、冲击性、密着性、韧性、耐蚀性及耐化学药品性能等。而户外用的粉末涂 料，除了上述的优点外，更包括了高耐候性及耐污染性。尤其是较厚的涂膜，粉末涂料一次喷涂可达到 50300μm，且流平性好，不会象溶剂涂料厚涂时会有滴垂或积滞等现象发生。 为了增进粉末涂料的多功能，可根据客户的喜好来调整颜色、光泽及表面平坦性能，甚至是特殊的金属粉 末涂料和一些特殊的皱纹粉末涂料。 4． 可观的经济效益 因粉末涂料使用静电原理喷涂，涂装设备可达到全自动化，无须浪费人力资源。即使需要人工辅助，涂装 人员不必经过长期训练，就可喷涂良好的涂膜。粉末涂料为 100%的固型成份且无需添加任何溶剂，节省包装， 降低储存空间。在喷涂过程中，如有喷涂不良的部位，可在未经烘烤前使用空气喷枪将其吹除，然后再喷涂上 去。因此不太可能发生表面流漆和滴漆的现象，从而降低了重涂返工的概率。在涂膜形成的成份中，溶剂型涂 料约为 60~65%，而粉末涂料几乎可达到 100%，且未附着于被喷涂物件的粉末可以回收再利用。一般而论，使 用粉末涂装技术，可以提高生产效率和经济效率。