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聚酯树脂基础

大多数用于涂料应用的聚酯树脂相对较低的分子量和非晶态, 线性的或分枝的,必须交联以形成有用的膜. As a class, 热固性聚ters generally provide better metal adhesion and impact resistance than thermosetting acrylics, however TSA’s provide coatings with better resistance to hydrolysis and weathering. The presence of ester linkages in the backbone of polyesters make them more prone to hydrolysis, 正确选择能给酯基键提供空间位阻的主链单体(例如 NPG 提供更好的耐水解性和耐候性.

过量反应物配方。聚酯树脂的基本成分

本文将只讨论饱和聚酯,它有时也被称为无油聚酯. Polyester coatings are a large portion of the construction, 汽车和航空航天市场,因为他们可以设计提供优良的性能,包括机械, impact, UV, and chemical resistance for use in waterborne, high solids low VOC and powder coatings. Linear聚酯 account for a large portion of the resins used for coil coating applications. When cured with melamine or blocked isocyanate can provide excellent flexibility, chemical resistance and light stability. Formation of polyesters is accomplished by 不断的聚合 含有至少两个羟基的醇和含有至少两个羧基的羧酸. Most often polyesters contain a blend of diols, 三醇和二元酸与过量的多元醇形成端羟基聚酯,与三聚氰胺或异氰酸酯预聚物反应形成涂层. 如果使用了过量的二元酸, the polyester is carboxy terminated for reaction with epoxy, 三聚氰胺或2-hydroxyalkylamides. 历史上聚酯合成被称为 缩聚反应 当一个醇和一个羧基反应生成水时. Other polyester synthesis routes include the reaction of an ester with an alcohol, 一种酸酐和一种醇的反应,最后一种内酯的开环聚合. When a diol (DD) reacts with a dibasic acid (CC) in equal molar amounts, the 分子量 逐步构建,并且更容易控制. 过量的反应物会有这个反应物的末端基团. For example:

The average molecule will have terminal hydroxyl groups. Branched polyesters are made from mixtures of monomer that contain one or more monomers which have a functionality F > 2. 作为单体的比例 F(功能) > 2 increases, 数均分子量增加,必须控制反应,避免凝胶化. A wide range of polyesters are in commercial use, for conventional polyesters cured with melamine or isocyanate prepolymers, the number average 分子量 is in the 2,000 to 6,000 range.

图1 -合成聚酯过程中分子量的增加:

graph of the increase in 分子量 - 聚酯树脂基础

Figure 2 – Common hydroxyl functional monomers are as follow:

formula for common hydroxyl functional monomers - 聚酯树脂基础

图3 -常见的二酸单体:

普通二酸单体配方。聚酯树脂的基本原理

表I -多元醇对聚合物性能的影响:

聚合物的影响表。聚酯树脂的基本原理
酸对聚酯树脂基面的影响表

表二-酸性功能单体对聚合物性质的影响:

如表一和表二所示, proper selection of co reactant monomers can provide a range of performance characteristics to provide an array of 性能属性 such as

  • 水解稳定性 癸二酸的,(NPG CHDA)
  • 表面风化 (npg, bepd, tmp, tme, hhpa, ipa)
  • hardness (npg, tme, tme, chdm, ta)
  • flexibility (AA, AzA, Seb, CHDA, TA, CDO)

通过选择合适的共混单体,结合聚合物体系结构的选择,以满足薄膜性能的要求,可以获得理想的性能.

聚合物设计要点图表。聚酯树脂基础

Lastly, 聚酯的结构可以用一个或多个反应基团进行修饰,以形成例如聚氨酯, oil, 或者丙烯酸改性聚酯.

有关聚酯的更多信息, 生物基树脂及原料, 请导航到 www.ulprospector.com.

Resources:

  • 有机涂料,科学与技术,弗兰克·N. Jones et.al., Wiley & Sons, 2017
  • Prospector

Remain Bug Free with 抗菌 Coatings

Ancient civilizations including those in Egypt, 中国和印度已经利用金属或利用铜的金属化合物, 银和锌可以对抗由微生物引起的疾病, 而古希腊人和埃及人则使用特定的霉菌和植物提取物来治疗感染. 自从SARS的到来, 以及最近的COVID - 19, there is an increasing awareness and use of antimicrobial materials including 抗菌涂料 防止致病微生物的传播. 抗菌涂料的市场价值估计超过3美元.2019年为20亿美元,预计调整后年增长率为10亿美元.4%到2026.

抗菌 (AM) agents in the form of paint additives act to either kill microorganisms or to stop their growth. 涂料中的抗菌添加剂可以作为涂料防腐剂或固化膜中的抗菌剂. Depending on the choice of antimicrobial additives these materials can function to kill or combat the growth of bacteria, virus, fungus and algae on the coating surface. 微生物控制可以通过使用抑制微生物繁殖或生长的抗菌技术来实现, 在医院和食品工业中提供卫生的表面,并保持漆膜的完整性.

This article will focus on antimicrobial additives and approaches to provide antimicrobial functionality in cured films. 在涂料中使用AM制剂来杀死或阻止以下微生物的生长,包括:

  • fungi
  • bacteria
  • algae
  • virus

Most biocides used in paints are migratory as they function by releasing the active ingredient to the surface of the coating when exposed to moisture. Longevity of the AM modified paint film depends on the rate of release of the biocide as the concentration of the active ingredient decreases with time.

描述释放的AM剂在油漆与时间-学习如何保持与抗菌涂料无Bug

The effectiveness of an AM additive in a cured paint is not only dependent upon concentration, resin system, gloss, PVC, 涂料表面结构及其所暴露的环境.

金属的使用如 silvercopper (and many 铜合金 ) and zinc 在各种形式的涂料中都是一种有效的抗菌添加剂. 银的抗菌作用有几种机制. One such example is that silver ions react with the thiol group in enzymes leading to cell death. The mechanisms through which copper acts to destroys cells includes the generation of hydrogen peroxide in the cells, 过量的铜也会与蛋白质结合,导致蛋白质分解成非功能性部分. Zinc pyrithione/2-propynyl butylcarbamate acts both a preservative and as a fungicide. The EPA oversees the regulation of antimicrobial agents and materials and determined that 铜合金 kill more than 99.9% of disease-causing bacteria within just two hours when cleaned regularly. Copper and 铜合金 are unique classes of solid materials as no other solid touch surfaces have permission in the U.S. 来证明人类的健康. Accordingly, the EPA has granted antimicrobial registration status to 355 different copper alloy compositions.

金属纳米粒子 including PVP and polysaccharide coated silver nanoparticles, MES-coated silver and gold have also demonstrated promise as antiviral agents. 铜纳米粒子have demonstrated antimicrobiological activity with Ecoli, fungus and bacteria.

使用certain 季铵硅烷 compounds also provide antimicrobial properties when bonded to a solid surface. Some examples include dimethyloctadecyl (3-trimethoxysilyl propyl) ammonium chloride, 烷基二甲基苄基氯化铵和二癸基二甲基氯化铵.

最近的文献揭示了表面结构对抗菌性能的影响作为一个 针像表面 structure formed by the bonding of 3-(trihydroxysilyl) propyldimethyloctadecyl ammonium chloride to the surface to destroy microbes by rupturing their outer membrane as they come in contact with surface spikes.

化学蒸汽沉积 二氧化钛 在紫外线照射下具有光催化活性. Its self-cleaning properties are due to its strong oxidizing power that results in anti-bacterial, 抗病毒和抗真菌活性.

超疏水表面 are those with a contact angle normally in the range of 150 degrees or greater. The surface structure is characterized by a needlelike micro-structure coupled with components that provide low surface tension. Such surface structures also have efficacy in reducing the ability of microbes to adhere to the surface thus imparting antimicrobial activity.

For additional information concerning the selection of materials to enhance hydrophobicity, 请导航到 www.ulprospector.com (EU).

Resources:

  • 有机涂料,科学与技术,弗兰克·N. Jones et.al., Wiley & Sons, 2017
  • Prospector
  • PCI Magazine
  • C & EN News
  • Science and Technology of Advanced Materials
  • Wikipedia
  • 全球市场的见解

聪明的涂料 – The Intelligent Choice

有很多定义 聪明的涂料然而,它们都有一个共同的特点,那就是能够感知环境并与之互动. Smart coatings offer additional functional value to that provided by traditional properties of protection and decoration. 透明市场研究公司(Transparency Market Research)的一份报告预测,全球智能涂料市场将以每年29美元的复合增长率扩张.8% during the period between 2017 and 2025 and reach 1 billion dollars in sales by 2024.

智能涂料中的外部刺激

智能涂料的外部刺激可能包括以下特性:

  • Anticorrosion
  • Antifingerprinting
  • Antifouling
  • Antimicrobiological
  • Antifungal
  • Color-shifting
  • Easy clean
  • 电致变色的
  • Hydrophobic
  • Hydrophilic
  • Ice-phobic
  • Photovoltaic
  • 压电
  • 压磁性
  • Self-healing
  • 太阳热反射
  • Super-hydrophobic
  • Thermochromic

These coating properties can be obtained by the use of novel specialty additives, 颜料和/或聚合物.

Icephobic涂料 either resist the formation of ice on the surface to which ice has poor adhesion or facilitate the release of ice that has formed on the surface. Icephobic涂料 have application in the aircraft industry, wind turbines and power lines. There are two types of ice formation that are problematic.

  • Rime ice, more commonly known as frost
  • Glare ice, 更常见的说法是釉冰, 是什么形成了一层连续的液态水并在其表面冻结. 耀眼的冰对电线和飞机特别危险.

An icephobic coating can either be formulated to work for rime ice or glare ice, but not both. For Glare Ice some degree of hydrophobicity is necessary, 然而,许多超疏水涂层的表面结构实际上可以增强冰的附着力. 超疏水涂层的低表面极性和表面结构使表面比预期的接触角更少的疏冰. 图1说明了.

Figure 1 - Learn more about smart coatings

一些研究表明,弹性聚氨酯涂层提供的冰的附着力比涂层的结构相似,但更多的玻璃性质. The theory is that the surface of the PU elastomeric coating induces slippage between the solid ice and that of the lightly cross-linked PU or silicone elastomeric structure with dangling chains at the surface.

Other approaches utilize freezing point depression on some surfaces or the addition of oils to low surface tension coatings. Lastly, 有些涂层利用添加剂来增加形成冰形核所需的过冷程度.

自我修复涂料

All coatings are susceptible to scratching and abrasion during their service life. 抓挠和磨损不仅对外观有不良影响, but further reduce the effective life expectancy in the event that the coating is applied over an oxidizable metal surface.

Seongpil一个等.Al研究了基于胶囊或纤维的自愈技术. 一旦涂层被刮伤, micro or nano-capsules containing catalyzed liquid polymerizable materials (e.g. drying oils, dicyclopentadiene) are released into the scratch. 图2说明了基于胶囊或纤维的自愈技术. 一旦胶囊破裂, 聚合作用是填充空隙,减少水分的进入,从而提高涂层的耐蚀性和外观. 基于热塑性聚(e-己内酯)的纤维分布在环氧树脂基体中,是自愈合技术的一个例子,可以在暴露于热时恢复膜的完整性.

Figure 2- Self Healing Coatings based on Capsules or Fibers

Figure 2 - Learn more about smart coatings

环境传感涂层

能够对环境的变化作出反应, 这些涂料具有多种用途. 例如,一些水性室内涂料含有一种染料,由于暴露在室内光线下或干燥过程中的pH值变化而改变颜色. Upon drying, the change in color from for example pink or purple helps to signify 足够的覆盖率 底毛颜色相似.

Coatings that contain a pH sensitive dye and fluorescent molecules are also used to 检测腐蚀. 另一种方法是在环氧涂料中使用罗丹明b基掺杂剂来检测钢和铝的腐蚀,因为它对pH值的降低和Fe的存在都有反应+++ ions.

Another fast growing area of smart coatings is the use of coatings that are modified to resist colonization of surfaces by viruses or bacteria. 大多数表面都含有微量的营养物质,如糖, 使微生物生长和繁殖的油或磷.


需要帮助寻找涂料?

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抗菌涂料

抗菌涂料 have utility in multiple applications including hospitals, kitchens, 公共浴室, 交通运输(出租车, Uber vehicles, airplanes) and on hand rails and door knobs. 已经成功使用的添加剂包括在各种粘合剂中含有银的材料,或吸附在多孔表面上,以使银缓释和延长使用寿命. Quaternary ammonium salts also provide antimicrobial activity, 季铵盐对病毒和真菌更有效. 铜还提供一些抗菌活性,以及有机抗菌,如三氯生.

表1 -其他智能涂层应用概述

Coating TypePrincipalStimulus智能响应
太阳能反射Reflect IR EnergyLight colors and dark colors using doped 混合金属氧化物sSunshine提供更凉爽的表面,节省空调成本
压电颜料在受力时产生电流(pb - zr -钛酸盐)Vibration当受到机械应力时产生电压
压磁多晶材料在受力时产生磁场VibrationCreates a magnetic field when subjected to 机械应力
Thermochromic液晶和亮色染料随温度变化而变色Temperature显示指定范围内的温度变化情况
电致变色的Polymeric electrolyte that changes color when exposed to an electric current电流Color change, aesthetic appeal, indicator
疏水/亲水Surface modification coupled with adjusting surface tensionMoistureAdjust water contact angle to repel (hydrophobic) or attract moisture (hydrophilic)

For additional information concerning the selection of materials to enhance hydrophobicity, 请导航到 www.ulprospector.com (EU).

  • 有机涂料,科学与技术,弗兰克·N. Jones et.al., Wiley & Sons, 2017
  • PCI Magazine
  • 科学指引
  • Shape Memory Assisted Self- Healing Coatings, 2013, Material Science, Luo and Mather
  • Transparency Market Research: 聪明的涂料 Market – Global Industry Analysis, Size, Share, Growth, Trends, 和预测2017 - 2025
  • Seongpil An, Min Wook Lee, Alexander L. Yarin, Sam S. Yoon, A review on corrosion-protective extrinsic self-healing: Comparison of microcapsule-based systems and those based on core-shell vascular networks, 化学工程杂志, Volume 344, 2018, 206 - 220页, ISSN 1385 - 8947, http://doi.org/10.1016/j.cej.2018.03.040.

The views, opinions and technical analyses presented here are those of the author or advertiser, 不一定是UL的勘探者.com或UL LLC. 所有内容受版权约束,未经UL或广告客户的事先授权,不得转载. While the editors of this site may verify the accuracy of its content from time to time, we assume no responsibility for errors made by the author, editorial staff or any other contributor.

A Guide to Providing Perfect Coating Adhesion

Paint films for nearly all aesthetic and functional applications above all else must provide adhesion to the desired substrate. Accordingly, one must take into account multiple considerations when formulating a coating that provides acceptable adhesion for the intended application. Critical considerations and how they impact adhesion include:

  1. 表面润湿
  2. Mechanical effects and internal stress
  3. 表面化学和结合强度
  4. Pigmentation
  5. 评价粘连

1. 表面润湿 -之间的关系 表面润湿 and adhesion is the first factor to be considered in designing a coating to optimize adhesion. If a coating in a liquid state does not spread spontaneously over the substrate surface, 这样,与基材表面形成机械和化学键的机会就有限了.

A liquid will spread spontaneously on the surface of a material if the surface tension (force/unit length or dyne/cm) of the liquid is lower than the surface free energy of the solid to be coated. For example, the image below provides a visualization of various degrees of wetting properties for a drop of liquid applied onto the surface to be wet.

Figure 1 – Images of Various Degrees of Substrate Wetting

Image of degrees of substrate wetting - A Guide to Providing Perfect Coating Adhesion

因此,在表1中,当 液体表面张力(LST)比 固体表面张力(SST), then wetting of the solid will occur. 这个差异越大, the greater the opportunity the liquid has to wet and spread on the surface of the solid. Waterborne paints have a more difficult time spreading on surfaces due to the relatively high surface tension of water in comparison to most organic solvents.

Accordingly, to improve wetting of waterborne coatings, 通常使用有机助溶剂和适当的润湿剂. In summary, when LST < SST, wetting occurs.

表1 -液体表面张力(LST)和固体临界表面张力(SST) (dynes/cm) @ 20°C

表面张力表-提供完美涂层附着力的指南

2. Mechanical adhesion and internal stress – The profile of the substrate the coating is to be applied to also can affect adhesion. Smoother surfaces are more difficult for coating adhesion as the surface area is lower and provides less area for the coating to interlock with the substrate. However, 如果涂层非常粗糙, it can be difficult for a liquid coating to wet and penetrate surface crevices. This is illustrated in the diagrams listed below in Figure 2.

Figure 2 Surface interactions between a coating and substrate

Image of surface interactions - A Guide to Providing Perfect Coating Adhesion

图B中的微观表面轮廓将提供比图A更好的附着力,因为涂层提供了更大的机会与基材联锁. Surface C has pockets and pores that are not easily penetrated by the coating, resulting in air pockets that can trap moisture and soluble ions resulting in blisters and corrosion (if substrate is an oxidizable metal) and thus poor long-term adhesion and eventual film failure.

In summary, from a mechanical adhesion standpoint, 具有低表面张力和低粘度的液体涂层有助于促进更好的润湿性和微观渗透(毛细管作用). Adhesion can also be adversely affected by stresses 这是由于涂层干燥或固化时收缩的结果. Environmental effects over time such as exposure to moisture, light, heat, pollutants and thermocycling also play an eventual role to degrade adhesion.

3. 表面化学和结合强度  除了表面张力和基材的表面轮廓外, 可用的基材官能团可为涂层组件的共价和氢键提供位点,以进一步增强与基材的粘接强度.

表2 -粘接力

Table of adhesive bonding forces - A Guide to Providing Perfect Coating Adhesion

As Table 2 illustrates, the highest bond strength to the surface is provided by 共价键, such as those provided for example the reaction of a dual functional trialkoxy silane coupling agent between the coating and the metal surface.

Most metal surfaces are supplied with a thin layer of oil to slow the rate of oxidation. 油也降低了表面的能量,因此更难被弄湿. 因为这个原因, 金属表面——例如钢, 镀锌钢和铝-通常在涂装前进行清洗,去除油,然后进行预处理, for example, 经过磷酸锌或磷酸铁处理的表面. 磷酸基的作用是增强涂层通过的附着力 氢键 金属表面与聚合物上的反应位点的关系.

图3经锌预处理的金属表面氢键的例子.Phosphate

氢键的配方-提供完美涂层附着力的指南

活性组 在聚合物的脊骨上或通过添加含环氧树脂的二聚或多功能附着力促进剂, amino or silane functional coupling groups can further react with a suitable pretreated metal 表面形成共价键,在金属和涂层之间提供附加的粘接强度.

For 玻璃或石英 rich surfaces, coupling agents such as amino silanes can also serve to enhance adhesion by reacting with a resin backbone containing an epoxy group with the alkoxy functional silane portion of the coupling agent bonding to the silica 形成硅氧烷的表面.

Plastics 是否因为它们的表面自由能较低,而脱模剂的存在可能会进一步降低它们的表面自由能,所以更难湿化. 通过紫外辐照提高聚烯烃的表面自由能,可以提高其对聚烯烃的附着力, 一旦使用了光敏剂, or flame treatment that generates hydroxyl, 羧基和酮基.

塑料表面上的这些官能团提供了更高的表面能来改善润湿性,并为涂层上的聚合物官能团提供了氢键位点. Other ways to improve adhesion to thermoplastics is to include an appropriate solvent in the paint to solubilize the plastic surface and enable intermixing of the coating at the plastic-coating interface.

4. Pigmentation – The level and type of pigment used in a primer not only affects coating substrate adhesion, 还要看它能附着在表面多久. Most primers are formulated at or slightly below Critical Pigment Volume Concentration (CPVC) to maximize topcoat adhesion (rougher primer surface and higher free energy) as well as many other coating properties (Figure 4).

Table of the Effect of CPVC on coating properties - A Guide to Providing Perfect Coating Adhesion

The use of more polar pigments may provide ease of wetting during the pigment dispersion process, 但可能会降低长期的附着力,因为它们更容易在涂层-基板界面上的水分迁移和剥离. 平板颜料和具有极低或无水溶性成分的颜料也能延长寿命.

Method A and B - A Guide to Providing Perfect Coating Adhesion

5. 评价粘连 有多种方法来确定和量化有机涂层对基材的附着力. Two of the most common means of determining adhesion include ASTM D3359 (十字舱口胶带粘接) and ASTM D4541(拉出附着力). ASTM D3359 describes two methods to determine cross hatch tape adhesion: method A is a simple X, 方法B是格子图. Method A is used in the field and for films > 5 mils, 而方法B用于实验室测定. 评级如下图所示:

Classifications are by area of the cross hatch removed by specialized adhesion tape and include:

5B (no area removed) > 4B (less than 5%) > 3B (5 – 15%) > 2B (15 – 35%),1B (35 – 65%) and 0B (greater than 65%)

ASTM D4541(拉出附着力利用一种装置来测量粘在涂层表面的移动小车的拉离强度. The device determines the force required to disbond the coating in pounds per square inch. This not only quantifies the amount of force required to pull off the coating, 还有失败的类型(粘性或粘性), how and at which layer the coating fails (topcoat to primer, 底材等的底漆.).

PosiTest AT-A - A Guide to Providing Perfect Coating Adhesion
PosiTest AT-A Automatic Adhesion Tester (SOURCE: DeFelsko)

Sources:

通过流变学获得更好的性能

具有无故障性能的油漆和有故障的油漆之间的区别在很大程度上取决于 rheology of the paint. Rheology is defined as the science of flow and deformation and influences properties such as:

  • Transfer 树脂和油漆
  • 颜料分散
  • Application (刷涂、辊涂、反涂或直涂、喷涂、圆盘涂和流涂)
  • 膜的形成 (flow, leveling and film coalescence)
  • 贮存稳定性 (resistance to hard settling of pigment)

相反,粘度可以定义为流动阻力. 如果不考虑和理解粘度,关于流量和流平的讨论是没有意义的. 简单的说, viscosity is the resistance of a liquid to flow and can be defined in measurable values. Viscosity is expressed as the relationship between shear stress and shear rate.

                       ϒ (shear stress) = F(力)/ A(面积)

                       D(剪切速率)= V(速度)/ C (thickness)

Shear rate 表示为秒and shear stress as dyne/cm2
Accordingly, viscosity can be expressed as shear stress / shear rate:

                       η (viscosity)  = ϒ (shear stress) / D(剪切速率)

由此得出粘度的单位为达因/厘米/ sec-1 或者达因秒/厘米or poise. 流体分为:

  • Newtonian (粘度与剪切速率的线性关系)
  • 触变性和假塑性 (随着剪切速率的增加,粘度降低)
  • Dilatent (随着剪切速率的增大,粘度增大)

Table 1. 粘度测量单位

粘度测量单位。了解更多关于油漆的流变性

Figure 1. 单点粘度测量. 多点粘度测量

单点粘度图-了解更多关于油漆的流变性

如图1所示, a single point viscosity measurement does not provide the information necessary to determine if a paint is Newtonian, 扩展或触变. Accordingly, to properly formulate a paint for various paint processes, it is necessary to know the viscosity characteristics over a range of shear rates. 多点粘度测定和流变性调整可以优化颜料分散, 树脂和油漆转移, application, paint flow, 找平和存储稳定性.

Viscosity characteristics of various fluids

image explaining the viscosity of various fluids - Learn more about the rheology of paints

Figure 2. 各种油漆工艺对粘度和剪切速率的要求

Graph indicating viscosity and shear rate - Learn more about the rheology of paints

如图3和图4所示,涂层工艺如树脂和油漆的粘度要求 transfer, pigment dispersion, application, film formation and storage stability 取决于流变学吗. For example, in high speed pigment dispersion and application properties, a degree of thixotropy (shear thinning) aids processing, sag resistance and settling resistance.

Fig. 3 Type of viscosity determinations for various processes

types of viscosity - Learn more about the rheology of paints

Fig. 4多种油漆工艺的流变特性

流变曲线图-了解更多有关油漆的流变特性

Fig. 5磨基配方的粘度要求

Millbase formulation - Learn more about the rheology of paints

Multiple 流变学/控制 可以使用 勘探者的搜索引擎 and are available to modify waterborne and solvent-borne paints to adjust application properties as well as for resistance to hard setting. 有多个 ingredients and variables that influence rheology in a coating formulation.

影响油漆流变性的问题包括:

  • 涂层成分
    • Binders (solution versus latex or dispersion)
    • Pigments
    • 填充颜料和填料
    • 颜料分散剂
    • Surfactants
    • Amines amount and type (waterborne paints)
    • pH值(水性)
    • Cosolvent
  • Customization of rheological properties
    • 流变改性和选择的标准
    • 流平剂
    • Surfactants
    • 其他添加剂

The viscosity of latex paints tends to exhibit excessive shear thinning behavior and is dependent on multiple compositional factors as listed above. 对乳胶涂料, 当粘度在高剪切率调整适当的应用, 适当调平时,在低剪切速率下,粘度趋于较高. 这就是为什么乳胶漆的流平性往往比溶剂型涂料差的原因. 这在较高的光泽水平上是最明显的. Accordingly, to counteract this phenomena, 联想增稠剂s are used. 用简单的术语, 联想增稠剂 can be defined as a water-soluble polymer containing multiple hydrophobic groups.

Some common thixatropes 他们的公司包括:

  • 有机粘土-在颜料分散步骤中添加
  • 氢化蓖麻蜡-冷却/加热激活时添加到研磨机的基础上
  • 聚酰胺-在冷却/热激活时添加到磨基上,或可在冷却/热激活时预激活并添加
  • 气相二氧化硅-在放气过程中添加

Rheology control agents for waterborne coatings include:

  • Cellulosics
    • 羟乙基纤维素
    • 羧基功能纤维素
    • 甲基纤维素
  • Polyamides
  • 合成粘土
  • 硅胶

联想增稠剂 types for waterborne coatings include:

  • 疏水改性聚氧乙烯基聚氨酯
  • HASE (Hydrophobically-Modified Alkali-Swellable Emulsions)
  • 疏水改性羟乙基纤维素
  • HEURASE – Hydrophobically Modified Ethoxylated Urethane Alkali Swellable Emulsion)

Fig. 6 ASTM D2801抗凹陷性-涂漆前(左图)和后(右图)添加流变改性剂的图像

sag resistance - Learn more about the rheology of paints

Figure 6. 用触控绳适当调整的油漆与修改前的左图对比,说明同一油漆的抗垂下性能的差异总之,流变性在提供颜料易于分散方面起着重要作用, 良好的流体传输, 可接受的应用性能和长期抗硬沉降能力. 有关流变材料的其他信息可以使用勘探者的搜索引擎的关键字,如流变学, thixotropy, 流和增稠剂.

Resources

探勘者知识中心 and Search Engine

Wikepedia

有机涂料,科学和技术,第三版,威利,威克斯.al. 2007

有机涂料,科学和技术,第三版,威利,琼斯e.al. 2017

www.warnerblank.com

快速增长的直接到金属涂层的部分

直接到金属涂层(DTM) 是涂料行业中一个快速增长的部分吗. 这种增长与效率提高带来的成本降低有关, time savings and fewer production steps. 这些涂料用于重工业、建筑产品和产品整理. 其中许多应用需要在苛刻的暴露条件下的性能,如石油钻井, 海上石油钻机和铸造厂. The compound annual growth rate of DTM coatings is estimated to be about 10%. DTM涂层可采用喷涂、刷涂、辊涂和卷涂等多种方式. Substrates include aluminum, cold rolled steel, 热轧钢 and coated metals (e.g. hot dip galvanized steel, galfan, galvalume, electrogalvanized steel and plated metals).

By definition, DTM涂层直接应用于金属表面,不需要大量的清洁或预处理. 理想情况下,这些涂层可以一步直接应用到金属上. However, DTM涂层还可以包括一层底漆和一层面漆,应用于适当准备以消除表面污染物和氧化物的金属表面. DTM涂层的主要优点是不需要多步骤的清洗操作, pretreatment and sealing prior to painting. 目前的DTM技术包括溶剂性、水性和高固体性. They can be one- or two-component acrylic, 环氧树脂或聚氨酯, or comprised of unsaturated polymers/oligomers that cure through polymerization.

基材润湿图像-了解更多直接到金属涂层

在设计提供长期性能的DTM涂层时,需要考虑多个问题. 这些包括:

  • 衬底的润湿
  • 最初的附着力
  • Longer term adhesion and corrosion resistance

衬底的润湿

金属表面的润湿 是影响初始黏附的主要因素吗. If the coating does not readily spread or wet the surface, adhesion will be adversely effected. Stating this in a another way–the surface tension of the substrate must be higher than that of the applied coating to ensure good flow and leveling. 在上图中, the blue sphere represents a paint droplet, 黄色的线代表一个金属表面. 右边的液滴完全湿润金属表面,从而提供了最好的粘附机会.

有两种方法可以保证基材的良好润湿. 从衬底的角度来看, 第一种方法是增加衬底的表面积, 通过磨蚀和/或喷砂. 这一过程也去除金属氧化物和氢氧根层,以提供一个更易于形成一个更持久的表面结合. 第二种方法是对涂料进行改性,以保证良好的润湿性(如涂布、涂布等).g. lower surface tension) through the addition of suitable wetting agents as well as solvents or co-solvents which may depress the surface tension.

Once adequate initial wetting is achieved, the second consideration is reviewing the factors that contribute to initial metal adhesion.


Need help finding direct to metal coatings?

勘探者可以帮助加快您的研究与技术数据表和访问全球设备供应商.

在这里直接搜索金属涂层


最初的附着力

最初的附着力 may be defined as the quality of adhesion to the substrate surface after the paint is cured, 但在暴露于自然风化和/或加速测试之前. 最初的附着力 of the cured film can be quantified by such tests as ASTM D3359 十字舱口胶带粘接 和/或ASTM D 4541 涂层的拉拔强度 它以磅每平方英寸来量化附着力. 需要加强的一些注意事项 最初的附着力 after volatiles have vaporized from the paint film include:

  • Resin systems with functional groups that promote bonding to the metal surface
  • 适当的粘附促进剂和偶联剂的存在
  • 交联的数量和类型

Resin systems with functional groups

Resin and crosslinker systems with the ability to form hydrogen bonds or 共价键 with the layer of oxide and hydroxide on the metal surface normally provide the best 最初的附着力. Long-term adhesion and corrosion protection depends on the resin backbone and crosslinking.

Metal Substrate - - Learn more about Direct to Metal Coatings

适当的粘附促进剂和偶联剂的存在

为了提高附着力,树脂和交联剂中含有大量的 active hydrogen donor and accepting groups 应该使用. 这种树脂含有一个或多个下列官能团:

  • 羧基(供氢基团)
  • 胺(接受氢基团)
  • hydroxyl
  • amide
  • urethane
  • phosphate (all hydrogen accepting or donating)

交联的数量和类型

Accordingly it makes sense why epoxies crosslinked with amino-amide groups (hydroxy, ether, 氨基和酰胺官能团), 聚氨酯和聚氨酯(例如来自湿气固化聚氨酯)对金属表面提供极好的附着力. Thus, they are used widely in direct to metal applications.

加上一个 合适的硅烷偶联剂 还可以提高初粘和长期粘接性能. A coupling agent is a molecule that is comprised of a reactive group on one end of the molecule ( Y ) for reacting with a functional group on the polymer chain with the other end of the coupling agent ( – Si – OR3 )与金属表面发生反应.

Formula 2 - - Learn more about Direct to Metal Coatings

在上面的分子中, the -OR groups attached to silicon can be methoxy or ethoxy, 分子的Y部分是一个官能团,比如氨基, epoxy, isocyanate, 丙烯酸甲酯或乙烯基. The reaction involves first hydrolysis of the alkoxy group to form a silanol which undergoes a further reaction with the hydroxyl groups on the metal surface. 另一端, or Y portion, 偶联剂与树脂骨架上的官能团发生反应.

公式2 -了解更多关于直接到金属涂层的知识

Table I- Examples of trialkoxy organofunctionalsilanes and their application

R =反应组开启R-Si (-OCH3)或R-Si (-OCH2CH3)R基团与活性硅烷ExampleTrialkoxy硅烷反应Application
Amino环氧树脂的功能 3-aminopropyl-triethoxysilane表面与- oh结合并自交联形成- Si - O - Si -Coatings for 玻璃以及Al、Zr、Sn、Ti、Ni的氧化物
Epoxy氨基功能3-glycidyloxypropyl trimethoxysilane表面与- oh结合并自交联形成- Si - O - Si -Coatings 用于玻璃以及Al、Zr、Sn、Ti、Ni的氧化物
Meth-acrylate丙烯酸树脂聚合3-methacryloxypropyltrimethoxysilaneSelf-crosslink with another silane to form– Si- O – Si – and with –OH on the surface湿固化树脂 提高附着力, physical and environmental performance
N/AN/AN-octyltriethoxysilane形式- Si - O - Si -疏水性, 提高疏水性
VinylVinyl or acrylic resin polymerizationVinyl-trimethoxysilane形式- Si - O - Si -湿固化树脂 提高附着力 and film integrity. 也用作 水分清道夫
Isocyanate羟基,氨基或巯基3-isocyanatopropyl-triethoxysilane表面与- oh结合并自交联形成- Si - O - SiCoatings for 金属及无机氧化物,也可以保湿
SilaneSIVO Sol-GelVOC Free Waterborne Surface Treatment 适用于各种金属和表面

Longer term adhesion and corrosion resistance

最后,提供 longer term adhesion and corrosion protection, DTM底漆应采用高质量的树脂体系, 含有防腐蚀颜料,抗潮湿渗透. The latter quality can be accomplished by increasing hydrophobicity and crosslink density. 持久耐湿底漆还具有抵抗固化膜水解的能力.

图2显示了一种能够提供优良基材润湿性的配方所能实现的防腐类型, 一流的初始粘附, 长期耐腐蚀,疏水性强.

Figure 2. Rust Armour primer with a two component urethane topcoat formulated by Chemical Dynamics–utilizing a high crosslinking resin system with and without combinations of hydrophobic pigment modification (SNTS).

10,000 ASTM B117 Salt Spray of Properly Formulated Direct to Metal 2 Coat Paint System (bottom row represents paint film removed).

Image of topcoats - learn about Direct to Metal Coatings

Long term corrosion resistance is an important consideration along with the selection of a resin/coating system that provides wet adhesion and minimizes the penetration of moisture and oxygen. As resin Tg and cross-link density increases, moisture and oxygen penetration decreases. In addition, 低渗透率有助于提供湿附着力,因为当涂层从其使用环境中移除时,较少的水将解吸. 具有大量芳香特性的树脂(双酚a基环氧树脂), polycarbonate and styrenated resins) have 低氧渗透率. Halogenated resins such as vinyl chloride, copolymers, chlorinated rubber and fluorinated polymers such as poly (vinylidene fluoride) all have low water solubility and thus 透湿率低1 (见表二).

In summary, DTM涂层的抗腐蚀配方是一项复杂的工作,并取决于金属基体, 服务环境, pigment level and type of resin selection. 有关制备缓蚀剂涂层的树脂和材料选择的其他信息, 请导航到 www.ulprospector.com.

Sources:

  1. www.faybutler.com/pdf_files/HowHoseMaterialsAffectGas3、焊接杂志.

References:

探勘者知识中心 and Search Engine

Zeno W. Wicks Jr., Frank N. Jones, Socrates Peter Pappas, Douglas A. Wicks. (2007). 有机涂料:科学与技术,第三版.

威利,琼斯e.al. (2017)《BOB娱乐体育(中国)》,《BOB娱乐体育(中国)》第四版.

Nanoscale Protection For High-Performance

最初发表于 欧洲涂料之旅07/08/2019

A new generation corrosion control coating technology with high crosslink density. By Atman Fozdar, Ronald Lewar- chik, Raviteja Kommineni, bob娱乐体育官网入口, USA.

图1:RA Exp1穿透铁锈并与母材结合的机理示意图.

An innovative technology that offers improved performance, saves material and labour costs and eliminates the need for an epoxy primer coat. A single component polymeric penetrant reacts with the corroded base metal to form a long- lasting bond and increase the structure’s useful service life. 这种涂层技术具有深远的潜力, for example in off-shore applications, 化学处理和汽车复饰.

低碳钢由于成本低,是各种应用中最常用的合金之一, abundant supply and easy fabrication. 但是钢的腐蚀是运输面临的主要问题之一.g. 汽车、飞机、船舶)和基础设施.g. pipelines, buildings, bridges, oil rigs, 炼油厂)直接影响其结构完整性的工业, 导致与钢结构的安全和维护相关的问题. According to the research published by NACE International [2], corrosion is responsible for losses over $ 2.每年5万亿. There are different methods to counter corrosion such as, 使用缓蚀剂衬里, 电镀, 有机聚合物涂层和化学气相沉积. Ap- plying protective organic coatings to metallic substrate, 特别是铝和钢, is an effective way to protect those substrates against severe corrosive environments. Organic coatings can minimise corrosion of metallic substrates by three main mechanisms: barrier, 牺牲和抑制.

We often see early signs of corrosion on a steel structure for a variety of reasons. 它可能是由于不良的表面准备或应用保护涂层或可能的环境因素,如酸雨, high humidity, 温度变化, 水气凝结, 化学烟雾, 和溶解气体的情况下,结构淹没在水或土壤. 在上述因素中, improper surface preparation is one of the most important factors that contributes to the corrosion of steel structures and can lead to loss of structural integrity and structure before the end of its useful service life. If there is a way to protect the structures after observing initial signs of corrosion, 无需经过劳动密集型的工作,如去除涂层, clean- ing, pre-treatment and recoating application, 这样可以大大增加它的使用寿命, 更有效率及更经济.

Table 1: Comparison of physical and chemical properties of RA Exp1 with other systems.

结果概览

  • We have developed a single component polymeric penetrant that can be applied with or without surface preparation over clean or lightly corroded steel/aluminium.
  • 该涂层包含纳米级活性材料,首先渗透到铁锈,然后迁移到未被腐蚀的金属表面, 聚合形成高度交联的保护性网络.
  • Results over cleaned pre-treated steel surfaces can exceed 10,000小时的盐雾喷涂,表面涂覆时无水泡或划线蠕变.
  • The new innovative technology offers improved performance, eliminates the need for an epoxy primer coat, 并节省劳动力和材料成本.

Experimental

用于RA Exp1的低分子量寡聚物的一个独特方面, is a prevalence of three types of reactive unsaturation on the resin backbone and low 分子量 reactive diluents. The three types of double bonds offer a synergistic curing mechanism that results in ancillary curing properties and high crosslink density that inhibits the penetration of soluble salts and moisture. Corrosion resistance is further improved when this resin blend is coupled with corrosion inhibitor pigments such as organically modi- fied zinc aluminium molybdenum orthophosphate hydrate and zinc-5-nitroisophthalate and unique conductive particles. RA Exp1如何穿透铁锈的图示见 Figure 1. 在基材表面穿透后, low 分子量 unsaturated monomers and oligomers, 与其他反应位点的化学键合/交联, 形成一个高度交联的网络,不透水和其他可溶性盐,加重腐蚀.

Hydrophobic and superhydrophobic variations of RA Exp1 were produced by adding superhydrophobic nano-textured silica [3]. This additive is naturally superhydrophobic having both hydrophilic/phobic sites and produces a volumetric hydrophobic coating. Hence, 即使固化涂层的表面由于在现场经历的正常磨损而磨损, 下面的层仍然会防潮. We formulated a separate design of experiments for RA Exp1 (with and without the additive) and 2-component polyurethane topcoat (with and without the additive).

Protection Demonstrated In Salt Spray Testing

将添加和不添加添加剂的RA Exp1分别应用于锌镍处理的冷轧钢板基体上, which was later top coated with a 2k polyurethane coating with and without the additive at 125 μm dry film thickness (DFT) each. 根据ASTM B117标准,在盐雾箱中进行盐雾试验, 之后,所有面板在室温下固化7天. Coated panels with an artificial defect (scratch with a dimension of 106 mm x 2 mm, created using a 1 mm scribe tool) were used to accelerate the corrosion process. All coated panels were placed in a test chamber at an angle of 45 ° and ex- posed to the 5.0 wt.% NaCl溶液,40℃. 凝结水收集速率和相对湿度至少为1.0 to 2.0 ml/h / 80cm2(水平采集面积)和95%. 进一步研究了涂层的保护性能,重点研究了涂层表面腐蚀或损伤区域的大小和分布,000小时的盐雾暴露.

Figure 2 shows 10,1000小时的盐雾博览会——当然, 四种系统中的三种以RA Exp 1作为底漆和2K聚氨酯面漆显示没有划痕或面起泡和/或腐蚀. 前四张照片显示了10年后不同的系统,000 hours of salt spray expo- sure and the bottom four photos show the extent of corrosion underneath the coating (of the same systems) after removing bottom half of coating using paint stripper.

Low Impedance Due To Conductive Nanoparticles

The barrier protection properties of RA Exp1 was investigated by performing EIS on Zinc phosphate pre-treated cold rolled steel, the results of which were compared with those of commercially available coatings based on conventional 2-component epoxy and moisture-cured urethane system. A three- electrode paint test cell (reference electrode: saturated Calomel electrode (SCE), counter electrode: working electrode: steel samples in 14.6 cm2 area) was used to perform the EIS measurements [1]. 在开路电位(OCP)保持在0的频率范围内进行阻抗定量.1 to 100 KHz and at amplitude sinusoidal voltage of ± 60 mV. 四个样本(RA Exp1, 2k epoxy and two moisture-cured urethane samples) were immersed in 40 mL NaCl solution (3.5 wt.%)和EIS测量在40天内进行.

初始Bode和Nyquist图(Figure 3a & 3b )表明,所有涂层的变化都表现出高阻抗值的电容性. RA Exp1 was found to have relatively lower impedance values compared with other control samples, 这可能是由于添加了导电纳米粒子和添加剂来增强耐蚀性,涂层的导电/防静电特性.

图2:ASTM B117, 10,000小时盐雾暴露.
图3a: RA Exp1, 2K环氧树脂,湿气固化聚氨酯的伯德图 & 2 (Initial). 图3b: RA Exp1, 2K环氧树脂,湿气固化聚氨酯的Nyquist图 & 2 (Initial).
图4a: RA Exp1, 2K环氧树脂,湿气固化聚氨酯的伯德图 & 2, after 50 days (1,000hours) of exposure.
图4b: RA Exp1, 2K环氧树脂,湿气固化聚氨酯的Nyquist图 & 2, after 50 days (1,000 hours) of exposure.

Greater Resistance To Electrolyte Diffusion

Figure 6 展示了半渗透涂层层保护的金属基板的简化等效电路, ignoring the coating resistance of negligible magnitude. The values of circuit elements in equivalent circuit networks can be used to directly characterise coating performance. 通过拟合等效电路模型得到的孔隙电阻(Rp)值作为曝光时间的函数,可以用来比较各种涂层系统的性能和排序. Figure 5 图中为孔隙电阻(RP)与. 曝光时间(小时), 说明2K环氧树脂的Rp随着时间的推移而降低,而, RA Exp1, 湿固化聚氨酯1和聚氨酯2对1几乎是恒定的,000小时暴露在3.5% NaCl溶液.

After 1,000 hours of immersion time, impedance values of moisture-cured urethane samples 1 & 而RA Exp1和2K环氧树脂能够维持它们的阻抗值而不显示出明显的下降. As shown in Figure 4a & 4b,湿固化聚氨酯2的性能由1常数变为2常数. This could be due to the diffusion of electrolyte to coating and substrate interface; hence, 涂层层以下可形成双层涂层. 其他样品包括RA Exp1, 没有观察到这种行为,这表明涂层更耐电解质和可溶性盐的扩散.

RA Exp1, 2K Epoxy and various moisture-cured urethane systems were spray applied on clean zinc phosphate pre-treated cold rolled steel and sanded cold rolled steel panel at 125 μm dry film thickness (DFT) and were allowed to cure at ambient temperature for a period of 7 days before characterising the physical and mechanical properties. Table 1 提供了新技术与其他系统的物理和化学性质的比较.

Figure 5: Log of Pore Resistance (Rp) Vs. exposure time.
图6 EIS测试等效电路图.
Figure 7: TGA curve/decomposition temperature of RA Exp1, 2K Epoxy and Moisture cured Urethane 1 & 2.

在极端条件下的潜在用途

Thermogravimetric analysis (TGA) was performed on RA Exp1, 2K Epoxy and moisture-cured urethane 1 & 2. The results indicate that RA Exp1 has comparatively higher decomposition temperature of 463.74 °C, whereas the decomposition temperature of other coatings ranges from 430-440 °C (Figure 7). This study confirms that the RA Exp1 can potentially be used in an environment where coatings are exposed to extreme conditions such as high heat i.e. 锅炉、化工加工设备、加压容器等.

High-Performance Two-Coat Corrosion Protection

这种新技术显著提高了金属基体的耐蚀性,例如:预处理过的铝, zinc-nickel treated cold rolled steel, lightly rusted steel and zinc phosphate treated cold rolled steel coated with RA Exp1. 结果表明,较好的抗面疱性, 根据ASTM B117的抗蠕变性能和整体抗腐蚀性能优于在此工作范围内测试的所有其他系统. The higher decomposition temperature per TGA analysis indicates a potential use of RA Exp1 for high temperature applications. 不同的乙烯基聚合反应和RA Exp1氧化固化的反应动力学还没有完全定义,仍然是一个研究的课题.

该技术的潜在应用包括:用于维护和维修的高性能防护涂料, 汽车再加工, 工业应用, 产品完成, 海上应用,如石油钻机和炼油厂, ACE行业, 还有锅炉, 化工加工设备和加压容器.

In conclusion, 这新一代的创新保护涂层和超疏水保护涂层提供了行业无与伦比的双涂层系统的腐蚀保护.

问阿特曼·福兹达3个问题

你推荐什么温度的固化达到最佳效果? Coating can be cured at ambient temperature similar to how most coatings are cured for maintenance and repair applications in the field but cure can also be accelerated by thermal bake. 环境赖斯- 7天后就可以获得全部的属性.

Did you test the laboratory results under reality conditions? 课题涂层已经应用 在多种基底上,如冷轧钢板, 磷酸锌冷轧钢材, 热轧钢, 2024 & 7075 Aluminum pretreated with hexavalent chrome sealer, Cadmium treated panels (used in aerospace) along with zinc-nickel treated substrates (used in aerospace and automotive). Acceler- ated properties such as UV-A exposure, ASTM B117 salt spray, Cleveland condensing humidity test 随着现实生活中暴露在一些温暖的气候地区附近的沿海地区,目前 being tested.

Are the high temperature loaded films you mentioned still corrosion resistant? Coated objects exposed to temperature in excess of 350–400 °C but less than 450 °C along with saturated steam exposure are performing well after few weeks of salt spray exposure (ongoing test). However, 这项试验是在受控的实验室条件下进行的. 现场评估仍是一个研究课题.

[1] MertenB.,CoatingevaluationbyElectro- chemical Impedance Spectroscopy (EIS) Report “ST-2016-7673-1” 2015.
[2] NACEInternational-http: / / inspectioneering. com/news/2016-03-08/5202/nace-study- estimates-global-cost-of-corrosion-at-25-trillion- ann. 2016
[3]辛普森J. et al. 2015 Rep. Prog. Phys. 78 086501.

特色照片:来源:尼古拉·扎布尔达夫-斯托克.adobe.com

Take Flight with Exterior Aerospace Coatings

航空航天涂料的外部应用要求一套苛刻的 性能属性 to provide acceptable performance from both a functional and aesthetic standpoint. In many cases the cost of a new commercial aircraft can be over $300 million with the expectation of lasting several decades with flight times of 4,每年工作时间在000小时或以上. 根据GMI, the aerospace coating market size is estimated to surpass $1 Billion in sales by 2024.

在勘探者知识中心了解制定航空航天外部涂层的挑战.

  • 在120华氏度到- 70华氏度的快速温度变化下,能在几分钟内保持附着力和柔韧性
  • 耐液压油,包括Skydrol,柴油,润滑油和除冰液
  • 在高海拔地区暴露在强烈的紫外线下,可抵抗降解
  • Repeated dry hot and cold moist cycles
  • 优异的耐腐蚀性,因为飞机经常在海洋和工业环境中操作
  • High degree of flexibility and resistance to stress as a result of turbulence, 振动和翅膀弯曲
  • Abrasion and erosion resistance and paint from dirt and sand at sub and supersonic speeds
  • 红外(IR)反射率(军事应用)
  • 低密度(节省重量)
  • Icephobic
  • Low COF

Looking for materials for aerospace coatings formulations?

UL Prospector®有近100个树脂列表, pigments, adhesives, 以及用于航空航天涂料的基本配方. 获取技术数据,要求样品,并联系供应商.

寻找航空航天涂层材料


The substrate 机身和飞机蒙皮主要是AA 2024铝. AA 2024 is an alloy of copper and aluminum. 铜提供了一个增加的强度与重量的关系, 然而,它也不利于耐蚀性. 减重是新飞机设计的巨大推动力,因为它相当于节省燃料, 速度和范围. 复合材料、金属纤维层合板和铝锂合金的应用越来越广泛.

A number of 清洁/预处理类型 (historically hexavalent chrome-based) provide a thin protective layer to improve corrosion resistance as well as receptivity of subsequent coats as it increases surface tension and polarity of the surface.

  • 有机涂料 typically include a primer, pigmented basecoat and a clearcoat.
  • Primers 典型的有机溶剂和水性双组分环氧-多胺/聚酰胺类型是否含有扩展剂, additives, 催化剂,并进一步加强与缓蚀颜料.

常见的类型 corrosion 飞机上包括 filiform点蚀,晶间,剥离,应力开裂,电蚀 and 缝隙腐蚀. All these types of corrosion are exacerbated by moisture, salt, 热循环和直接接触金属的金属含量不同.

Common corrosion inhibitive pigments historically used in aerospace primers include barium chromate and strontium chromate. Epoxy resins for the most part are combinations of bisphenol A and bisphenol F types. 当与适当的交联剂(通常是胺或酰胺胺型)配制时,环氧基底漆具有极好的附着力, corrosion resistance and chemical resistance.

涂层铝的丝状腐蚀-在勘探者知识中心了解有关外部航空航天涂层.
Figure 1. 镀铝表面丝状腐蚀的图像
Cross-section of Aerospace Coating Layers - learn about exterior aerospace coatings in the 探勘者知识中心.
Figure 1a. Cross-section of Aerospace Coating Layers
Typical epoxy resins and epoxy functional reactive diluents used in aerospace primers. Learn more about aerospace exterior coatings in the 探勘者知识中心.
Figure 2. Typical epoxy resins and epoxy functional reactive diluents used in aerospace primers
具有氨基功能的环氧树脂的反应。在勘探者知识中心了解外部航空航天涂层.
Figure 3 Reactions of epoxy resins with amino functionalities

航空航天外观面漆 are two-component urethane types comprised of hydroxyl functional resins [polyesters, acrylics or fluorinated ethylene vinyl ethers (FEVE)] reacted with isocyanate prepolymer(s). Typical curing reactions are as follow:

Reactions of polyols with isocyanate functional cross-linkers - learn about exterior aerospace coatings in the 探勘者知识中心.
图4多元醇与异氰酸酯功能交联剂的反应

由于航空航天涂层系统的苛刻要求, 化学家使用化学计量过量的异氰酸酯交联剂来提供优良的耐化学性. 过量的异氰酸酯交联剂与水分反应脱羧形成聚脲. Typically a 50 percent or more stoichiometric excess of isocyanate is used to ensure a high degree of polyurea formation.

聚氨酯以其对Skydrol(一种飞机液压油)等腐蚀性液体的卓越耐蚀性而闻名. 聚酯多元醇are used primarily in the pigmented basecoat portion of the two component polyurethane coating, whereas 丙烯酸多元醇 and also FEVE-based多元醇 主要用于聚氨酯面漆的清漆部分吗.

Clearcoats are further fortified with both UV absorbers as well as hindered amine light stabilizers to further protect the coating system from degradation due to exposure to intense upper atmosphere UV light.

异氰酸酯交联剂 are typically derived from hexmethylene diisocyante (HMDI) and/or isophorone isocyanate (IPDI). The former type provides flexibility, whereas the latter can provide improved hardness.

由三个HMDI分子反应形成的缩二脲-在勘探者知识中心了解外部航空航天涂层.
图5三个HMDI分子反应生成双缩脲
Isocyanurate formed from the reaction of three HMDI molecules - 探勘者知识中心
图6三个HMDI分子反应生成异氰脲酸酯
Uretdione formed from two HMDI molecules, as used in exterior aerospace coatings
图7两个HMDI分子形成的脲二酮
异佛尔酮二异氰酸酯-在探矿者知识中心了解其在外部航空航天涂层中的使用
图8异佛尔酮二异氰酸酯

Isocyanurate以异氰酸酯为基础的交联剂在与合适的多元醇树脂体系反应时具有优良的耐候性,因此广泛应用于航空航天面漆中.

Recent innovations and project emphasis in aerospace coatings include chrome-free pretreatment-primers and chrome-free epoxy primers. Drag-reducing topcoats that provide a 1 percent improvement in fuel efficiency can lower fuel costs by $700 million a year, 根据国际航空运输协会(IATA). On average, airlines incur about $100 a minute per flight in total operating costs, IATA says. Therefore, 即使只节省一分钟的飞行时间,每年也能使整个行业的运营成本减少10亿美元以上,并显著减少环境排放.

进一步阅读:

References:

  • Active Protective Coatings, Springer et.al., 2016
  • 有机涂料 Science and Technology, 3rd 版,威克斯等.al, 2007

Get a Reaction with Urethane Coatings

聚氨酯涂料 have come a long way since their invention by Otto Bayer and coworkers in 1937. Depending on the choice of oligomeric and polymeric materials, 由于其通用性,这些涂料被用于各种要求高性能的应用. 它们可以是硬的或软的,柔性的或刚性的,耐化学药品,并提供极好的附着力.

Polyurethane properties and applications

  • Outstanding moisture and corrosion resistance
  • 柔性底漆和面漆
  • 耐候性(脂肪族多异氰酸酯配以合适的耐久多元醇)
  • Resistance to acid rain and other chemicals
  • One component
  • Two component
  • Waterborne one component bake finishes
  • 100% solids
  • 粉末涂料
  • Waterborne ambient cure two component finishes

Polymeric and isocyanate prepolymer components include one or more isocyanate prepolymers and one or more polymeric or oligomeric components containing hydroxy functionality or other active hydrogen group. 异氰酸酯是 活性与功能 其中包括:

  • Hydroxy
  • Amino
  • Imino
  • Ketimene
  • 羧基(形式有限公司2)
  • Urethanes
  • Ureas
  • Acetoacetylated树脂

The active hydrogen for exterior weatherable coatings is normally an aliphatic hydroxyl group in a polyester or acrylic polymer. 醇和酚与异氰酸酯反应生成 urethanes.


Need help finding polyurethane coatings?

勘探者可以帮助加快您的研究与技术数据表和访问全球设备供应商.

在这里搜索聚氨酯涂料


氨基甲酸乙酯的反应

下面的反应R1 and R2 可以是脂肪族还是芳香族.

R1-R2-aliphatic-or-aromatic formula - Learn more about polyurethane coatings

The urethane reaction is reversible at higher temperatures. For baking systems such as those using blocked isocyanates, 过高的烘烤温度会导致脆化, 变色、防潮、耐腐蚀性能下降.

As a general rule, reaction rates for urethane formation is in the following order:

primary hydroxyl > secondary hydroxyl > tertiary hydroxyl. 逆反应速率是正反应速率的倒数. 例如,叔羟基生成的聚氨酯就相对不稳定.

一旦形成,聚氨酯就可以与异氰酸酯进一步反应而形成 allophanates:

Allophonates formula - Learn more about polyurethane coatings

异氰酸酯和多元醇的其他环境固化反应如下:

isocyanate-polyol - Learn more about polyurethane coatings

正如上文所述, 在多元醇和异氰酸酯之间形成聚氨酯所需的交联反应涉及多个 竞争反应. 因为这个原因, two-component formulations with polyol in one component and isocyanate in a second component are normally formulated with a 10%或以上的化学计量量过量 of isocyanate to overcome 竞争反应 with moisture and other possible reactants.

聚氨酯催化剂

Catalysts for polyurethanes include tin based carboxylates such as dibutyl tin dilaurate, 二丁基辛酸锡或叔胺,如DABCO [N2(C2H4)3]. 的毒性问题, 也有基于十酸铋的无锡催化剂, 2-乙基己酸铋或其他金属羧酸盐.

异氰酸酯和uv—

有多个 aliphatic and aromatic polyisocyanates available for use in ambient cure two-component solvent born, 100%固体液体或粉末, 以及水性油漆. 了异氰酸酯 are used in single component baked coatings as they unblock at an elevated temperature to activate the isocyanate group. The reaction sequence is first unblocking and then addition. Polyurethanes formed from aromatic isocyanates are used primarily in primers and interior coatings due to poor light stability, 但具有优异的防潮、耐腐蚀性能.

常见的脂肪族和芳香族多异氰酸酯结构块包括:

polyisocyanate building blocks formulas - - Learn more about polyurethane coatings

HDI和IPDI用于合成高分子量的异氰酸酯预聚物,其中可能包括异氰尿酸酯, 阿洛泮酸和尿路二酮改善卫生, 处理和风化性能.

Isocyanates can be blocked to form a stable material for use as a crosslinker in single component polyurethane coatings. 了异氰酸酯 广泛用于粉末中吗, waterborne and high solids baking finishes for coil primers, 汽车涂料和电沉积涂料. Common blocking agents include 2-ethylhexanol, e-caprolactone, methyl ethyl ketoxime and 2-butoxy ethanol. 当与多元醇混合时, 封闭的异氰酸酯在达到解除封闭温度之前是稳定的,然后消除封闭剂并与多元醇反应形成聚氨酯.

水性双组分聚氨酯 coatings can be made using water dispersible isocyanates. 水分散性IPDI或HDI基异氰酸酯在商业上是可获得的,是由部分异氰酸酯基团与聚乙二醇单醚反应制成的. The polyisocyanate is then added into a separate dispersion containing the polyol to form separate dispersed particles that crosslink and form a film.

Iso-free技术

基于异氰酸酯的技术已经受到越来越严格的审查,因为接触异氰酸酯会导致哮喘和其他呼吸系统问题. 职业性哮喘已经取代石棉沉滞症成为新的与工作有关的肺部疾病的主要原因. 异佛尔酮免费技术 提供不暴露于游离异氰酸酯的聚氨酯形成. 在过去的几年里 isofree技术已经出现,不利用异氰酸酯交联剂形成聚氨酯,从而消除异氰酸酯暴露. 利用Isofree 2K技术 聚碳酸酯和聚醛 for example includes improved sprayable pot life and rapid cure and early hardness. Technologies that form polyurethanes without the use of an isocyanate crosslinker follow:

  1. Hexamethoxy methyl melamine + Polycarbonate → Polyurethane
polyurethane formula - Learn more about polyurethane coatings
  1. Polycarbonate + Polyamine → Polyurethane
polyurethane formula - Learn more about polyurethane coatings
  1. Polycarbamate + Polyaldehyde → Polyurethane
polyurethane formula - Learn more about polyurethane coatings

The formation of polyurethanes in reactions #1 and #2 are sluggish at room temperature, 而3号的反应速率 crosslinking reaction of a polycarbonate and a polyaldehyde 更温和的. Polyurethane formation by this reaction route provides a longer sprayable pot life and at the same time a faster reaction rate after application than that provided by the use of an isocyanate crosslinker.

Sources:

Prospector 知识中心 and Search Engine

Polyurethanes. (2017). The Essential Chemistry Industry – online.

马亨德拉,Vidhura. (2016). 用松木树脂制造泡沫. 10.13140/RG.2.1.2065.0004.

Wikepedia. Polyurethane.

John Argyropoulos, Nahrain Kamber, David Pierce, Paul Popa, Yanxiang Li and Paul Foley. Dow Isocyanate Free Polyurethane Coatings – Fundamental Chemistry and Performance Attributes, European Coatings Conference, April 21, 2015.

Zeno W. Wicks Jr., Frank N. Jones, Socrates Peter Pappas, Douglas A. Wicks. (2007). 有机涂料:科学与技术,第三版.

威利,琼斯e.al. (2017)《BOB娱乐体育(中国)》,《BOB娱乐体育(中国)》第三版.

涂层老化的原因及缺陷:涂层老化的评估与测试

外部风化可以对美学产生戏剧性的影响, 涂料的功能和物理特性,包括垩白, film erosion, cracking, color change, etching, blisters, peeling, spotting, 以及硬度损失, 灵活性(提高玻璃化转变温度, or Tg)、光泽度和附着力. Multiple 制定问题 influence the performance of coatings in a given exterior environment and include:

  • Resin Type
  • 交联剂类型
  • 颜料/颜色
  • Pigment type
  • 颜料与粘结剂比
  • 催化剂的存在
  • 添加剂的选择

需要帮助研究涂料的抗氧化剂和紫外线吸收剂?

勘探者可以帮助加快您的研究与技术数据表和访问数千种材料的全球供应商.

今天就创建你的免费帐户!


What impacts exterior coating weathering?

其中一些因素将比其他因素更详细地讨论它们对风化的影响程度. 影响外部风化的主要问题包括: 光致氧化 (氧气和光的存在)和 hydrolysis 由于水分、热量和光的影响. 前者可以在适当的使用下减轻到一定程度 UV absorbers 以减少聚合物基质暴露在紫外线下, antioxidants and hindered amine light stabilizers (HALS) to reduce the effects of associated oxidative degradation.

光氧化和水解都被温度的升高所加剧,因为两者都是热激活的. 空气中高湿度盐和/或酸雨环境(高硫酸盐, 硝酸盐)和臭氧加速树脂体系的水解和降解,并加速颜料因酸侵蚀而变色.

By far the major process that influences film degradation of polymeric coatings is 光致氧化. 氧化降解通过自催化过程从聚合物中提取氢进行. Accordingly, 达到优良的风化效果, 避免或至少尽量减少聚合物中更容易抽氢的官能团. 以下是活性亚甲基抗氧化降解功能基团的一般顺序 (- CH2)之间的双键或邻近胺基的最差:

活性亚甲基基团抗氧化降解功能基团的顺序-在勘探者知识中心了解更多关于涂层风化测试的信息.

Accordingly, 一般来说,含氟聚合物和硅氧烷比聚酯或聚氨酯更耐用,其次是芳香含量高的树脂体系, and amine groups being the least durable. The later types include aromatic epoxies.

的特点 紫外线稳定剂 包括吸收和猝灭. UV absorbers 通过吸收聚合物系统吸收的波长区域的辐射,从而起到屏蔽树脂降解的作用. Ideally 紫外线稳定剂 should have a high absorption in the UV region from 295 to 380nm to provide protection for the polymer from degradation. The most effective UV stabilizers are also more permanent thus ensuring longer life once incorporated into a paint system.

紫外线稳定剂将吸收的紫外线能量转化为热量,例如2 -羟基二苯甲酮:

2 -羟基二苯甲酮的化学公式-在勘探者知识中心了解更多关于测试涂层的风化情况.
Chemical formula for 2 – hydroxy benzophenone

Antioxidants 可分为两组预防剂(过氧化氢分解剂和破坏链的抗氧化剂). 过氧化物分解者包括硫化物和亚硫酸盐. 断链抗氧化剂破坏的链传播步骤 autoxidation. 有机材料与分子氧反应的过程称为 “autoxidation“. Autoxidation 是由热量引发的, 光(主要在紫外线区), 机械应力, 催化剂残留物, 或与杂质反应生成烷基自由基. 自由基可以, in turn, 反应并导致聚合物降解,如下图所示:

自氧化循环图像:降解-在知识中心了解更多关于如何测试涂层的风化情况.

受阻胺光稳定剂 (HALS)既是打破链的抗氧化剂,也是过渡金属的络合剂. For coatings that provide excellent durability, the rate of Hydrolysis 通常比光氧化低得多吗.

The rate of hydrolysis for functional groups is esters>carbonates>ureas>urethanes>ethers.

For crosslinked products, melamines hydrolyze at a faster rate than that of aliphatic urethanes.

As most systems used in exterior applications contain pigment (including basecoat/clearcoat systems used in exterior automotive topcoats); 颜料的选择,颜色以及颜料的体积浓度 (PVC) 所有这些都有助于油漆系统的耐久性. PVC的选择多少取决于光泽度, 颜色要求和可接受遮盖物所需的薄膜厚度(基板上的颜色均匀性).

In paint systems dependent on protection provided by pigment for light stability, 耐久性更多地依赖于PVC相对较小的变化. 颜色和风化作用之间的关系可能非常复杂. For example, darker colors tend to absorb more radiant energy and thus the heat absorption coefficient for darker colors not using solar reflective pigments is higher, contributing to higher temperatures of the coating exposed to exterior radiant energy:

有机涂层基材在阳光下使用常规颜料积累热量的图表-在勘探者知识中心了解更多关于涂层风化测试的信息.

Higher temperatures contribute to higher degradation rates, 然而,较深的颜色(棕色/黑色)吸收更多的紫外线/可见光能量,从而有助于保护聚合物系统免于降解. Accordingly the use of a resin system prone to oxidative degradation at higher temperatures will provide poor weathering especially in dark colors.

颜料的选择 在一类颜色可以有一个巨大的影响,耐久性在一类聚合物. Pigments used for color and hiding can be divided into two general classes including 无机和有机.

无机颜料 as a class are more resistant to degradation and chemicals than are organics. Some of the durable in有机颜料 include acid resistant aluminum flake, 云母氧化铁, yellow, 棕色和红色的氧化铁.

The most durable in有机颜料 are 陶瓷颜料. 陶瓷颜料 是混合金属氧化物. As these pigments are fully oxidized they are very resistant to chemicals and oxidation. 许多明亮的颜色需要 有机颜料,这些色素是必需的. Many 有机颜料 能否提供优异的抗外部降解性,并广泛应用于汽车底漆中.

如何评估涂层的耐候性

最好的方法是 评价风化 是自然曝光的颜色吗, environment, gloss level and exposure angle the coating will be used in. 由于这对于新涂层的引入是不实际的,加速风化是必要的.

South Florida weathering is normally the most accepted means to determine accelerated natural weathering of a coating. 例如:5度水平朝南用于汽车应用,45度或90度朝南或朝北用于建筑应用.

Marine environments are also commonly used for paint systems to evaluate corrosion protection or resistance to biological growth. Although South Florida weathering provides a good indication of the projected durability, there is always a desire to further reduce the time required to predict the durability of a coating to an environment high in UV, moisture, 和高温.

A few of the other commonly used methods to determine accelerated weathering include ASTM D 4587 (QUV weathering) and ASTM G155/ASTM D7869 (Xenon Arc). These accelerated weathering devices provide a combination of cycles of intense UV light, 温度高、湿度大. There are a number of articles detailing the correlation or lack thereof with natural weathering including new instruments and processes that profess to provide a better correlation to natural weathering.

Graph of Xenon with daylight filter - learn more about how to evaluate coating weathering in the 探勘者知识中心.
Chart of coating weathering results - learn more about how to evaluate coating weathering in the 探勘者知识中心.

来源和进一步阅读:

The Source for Chemical Coatings Consulting