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[复制链接] 只看楼主 倒序阅读 楼主  发表于: 2013-12-29
Understanding the Basics of Chemical-Resistant Polyesters and Vinyl Esters

Gary  R.  Hall
Consultant
Gary R. Hall, now retired, was manager of research and development at Sauereisen, Inc. (Pittsburgh, PA). He was with Sauereisen for 45 years. Hall is active in NACE, ASTM, and the American Institute of Chemical Engineers. He is a contributing editor for JPCL and also is a recipient of one of JPCL’s 2012 Top Thinker awards.


Outside view of Bunker C crude oil storage tank with a floating roof. Surface preparation of the tank interior will be followed by application of a vinyl ester coating.
All photos courtesy of Sauereisen


Unsaturated polyester resins based on maleic and fumaric acids have been known since the 1920s. In the late 1930s, the modern form of these resins was introduced when Charleton Ellis combined styrene with unsaturated polyester.

Polyester and vinyl ester resins have been used in severe chemical environments for 50 years in the form of mortars for chemical-resistant brickwork and in fiberglass reinforced plastic (FRP). These successes led to the development of chemical-resistant coatings and linings based upon these resins that offer superior resistance to a broad range of chemicals, especially acids, and to higher temperatures than most other coating types like epoxies and polyurethanes.1

The terms “coatings” and “linings” are used throughout this article. For the purposes of this article, linings are composed of glass fabric, mat, or woven roving saturated with the chosen resin. They are applied in sheets of fiberglass reinforcement saturated in resin, which are then laid against the substrate and rolled in place using a ribbed roller. Coatings are usually thinner than linings and are applied as a mixture by brush, roller, airless spray, and plural component spray.

This article describes the basic chemistry of polyesters and vinyl esters, properties, concerns with the materials, and application methods.

Basic Chemistry
Unsaturated polyesters are formed by the reaction of a dibasic organic acid, such as phthalic or maleic acid, and an alcohol or polyol such as ethylene glycol. Unsaturated polyester resin (usually called a “polyester resin” or “polyester”) is a thermoset that can be cured from a liquid state under the proper conditions. A wide range of polyesters, including partially aromatic and aromatic versions, can be made by using different acids, glycols, alcohols, and monomers, each with different properties (Fig. 1).

Polyester resins used in coatings are typically pale-colored, viscous liquids consisting of the polyester dissolved in a monomer, usually styrene. Styrene reduces the viscosity of the resin, making it easier to handle. Styrene is called a reactive diluent because it is involved in the curing of the polyester resin, as well as in reducing viscosity. They cure through a free radical mechanism. The free radicals are produced by reaction of an organic peroxide, such as methyl ethyl ketone peroxide (MEKP), and a reducing agent, typically a cobalt salt. This type of free radical initiation is known as a redox (reduction-oxidation) reaction. When added to the resin, the MEKP splits into two free radicals [RO• + ROO•], each of which then react with the styrene, causing it to form another free radical.

These styrene radicals then react with the carbon-carbon double bonds (-C=C-) adjacent to the ester groups along the length of the polyester resin molecules forming cross-links between adjacent polymer molecules, without creating by-products. The uncured polyester molecule has multiple reactive sites along the length of the molecule. Multiple cross-link sites ensure that the molecules are tightly bonded to each other. This allows for high mechanical strength and excellent chemical resistance, but it also introduces rigidity to the cross-linked network. This irreversible reaction results in a dense and complex network of intertwined polymers with excellent chemical resistance. Polyester resins and vinyl ester resins are highly reactive, have a short shelf life, and will gel or set on their own upon standing. Warm temperatures hasten this reaction. Inhibitors are often added during manufacture to prolong storage life. Refrigeration is also often recommended. Even with the use of inhibitors and refrigeration, the shelf life of polyester and vinyl ester resins is typically three months or less.

Saturated dicarbonic acids are used in polyesters to control cross-link density and to optimize the properties of the cured polymer network. The three most commonly used dicarbonic acids and their contributions to the cured network are shown in the box on p. 36.

To formulate vinyl ester and polyester coatings, the coating manufacturer will add other materials, including initiator; accelerator; and typical coating raw materials such as thixotropes, fillers, and pigments. Flake glass and silane-treated micaceous iron oxide (MIO) are often preferred fillers because they beneficially reduce coating permeability. Fillers are often in the range of 45–50% by weight. There is also some evidence that flake glass will help limit the length of cracks that may form in the coating due to stresses in service.

Fig. 1: Unsaturated polyester polymer.

Vinyl ester resins, a special subclass of polyesters, are similar to polyester resins in that both contain multiple ester groups and are cured in the same way. There are, however, some significant differences in the polyester resins and vinyl ester resins used to formulate corrosion-resistant coatings. The main difference is that a polyester resin molecule has several reactive ester sites along its length, while a vinyl ester resin has only two ester groups, both in the terminal or vinyl position. This has a significant effect upon the properties of the resulting cured polymer. Since the reactive sites in a vinyl ester resin are only found in the terminal positions of the chain, cross-linking can only occur at these sites, in contrast to several cross-link sites on a polyester chain. Terminal attachment between two polymer chains means that, unlike what occurs in polyester polymers, the entire polymer chain between reactive ester sites is not cross-linked to another polymer chain. The portion of the polymer chain that is not cross-linked is able to absorb shock and impact, making vinyl esters tougher and more resilient than polyesters.

Having only two ester groups per molecule imparts an additional advantage to vinyl esters. In aqueous environments, ester groups are susceptible to hydrolysis, which causes degradation of the polymer; thus, vinyl esters exhibit better resistance to water and many other chemicals than their polyester counterparts. For these reasons, vinyl esters are often used in highly corrosive environments where other resins fail. Vinyl esters will also function at higher temperatures than polyesters and epoxies. The structure of the polymer between the reactive sites has a profound effect upon the chemical and physical properties of the vinyl ester resin.

The vinyl ester resins most often used in chemical-resistant coatings have an epoxy backbone to which terminal ester end groups are attached. These resins are the reaction products of an addition reaction of an epoxy resin with an unsaturated carboxylic acid, which results in terminal double bonds. Several epoxy resins are used in commerce. The bisphenol a diglycidyl ether epoxy, typically called bis A epoxy, and the epoxylated phenol-formaldehyde novolac, typically called novolac epoxy, are the two most commonly used. The epoxy vinyl ester resins produced are frequently referred to as bis A epoxy vinyl ester resins and novolac epoxy vinyl ester resins respectively. Commonly used acids include acrylic acid, methacrylic acid, isophthalic acid, terephthalic acid, maleic anhydride, and fumaric acid. The physical and chemical properties of the resulting vinyl ester resin depend on the type of epoxy resin used, its molecular weight, and the acid used (Fig. 2).
Fig. 2: The physical and chemical properties of epoxy vinyl ester resins depend on the type of epoxy resin used, its molecular weight, and the acid used.


Other modifiers can be used to impart special properties. For example, toughened vinyl esters can be made by incorporating modified liquid rubbers like carboxy-terminated butadiene-acrylonitrile co-polymers (CTBN), epoxy-terminated butadiene-acrylonitrile rubber (ETBN), core shell rubbers, and certain vinyl-modified hybrid urethanes. Toughening vinyl ester resins is usually done to increase properties like temperature resistance, glass transition temperatures (Tg), heat distortion limits (HDT), water resistance, and fracture toughness. Generally, when additives are used to improve elongation and flexibility, chemical resistance will decrease. Flexibilized polyester and vinyl ester resins are typically limited to formulating primers and are rarely used as topcoats.

There is considerable interest in two newer technologies for curing vinyl ester resins. Styrene is a prohibited ingredient in some applications, such as in potable water or in contact with food, and for some customers due to health considerations.

Cobalt carboxylates have already been classified as “CMR2 Reprotoxic” by the European Chemical Agency (ECHA), which means they are carcinogenic, mutagenic reproductive toxins. In Europe, manufacturers must conform to a wide-ranging directive known as REACH (Registration, Evaluation, Authorization, and Restriction of Chemicals). European manufacturers are under pressure to eliminate cobalt (Co+2) from coatings and composites. All other cobalt compounds will eventually be evaluated, and those that are capable of forming the Co+2 ion will be prohibited. Cobalt napthanate and cobalt octoate will both form the Co+2 ion. This means that manufacturers must search for replacements for both cobalt salts and styrene. Other transition group metals such as copper, manganese, and iron have the ability to start the redox reaction needed to initiate the cure, without having carcinogenic or mutagenic characteristics. Other monomers may be used in place of styrene, some of which are neither hazardous air pollutants (HAPs) nor volatile organic compounds (VOCs), resulting in a “styrene-free” vinyl ester. These other monomers include tert-butyl styrene, vinyl toluene, diallyl phthalate, and trimethylolpropane triacrylate. The latter two are neither HAPs nor VOCs and are more expensive.

The use of ultraviolet light (UV) to cure vinyl ester coatings is gaining in interest and in importance. These coatings also use free radical initiators to initiate cure, but instead of MEKP, a photo initiator is added to the resin. When exposed to UV light, the photo initiators become “excited” and then decompose to generate the free radicals. Radiation-cured resins offer the potential to reduce air pollution and to reduce carcinogens in the environment because they are solvent free. In practice, UV-curable vinyl esters are somewhat limited in their applications because the uncured coating must be exposed to the proper wavelength of UV light at the required intensity. This generally requires placing the UV light source close to the freshly applied coating, while maintaining a uniform distance from the coating. This is not always possible, especially at construction sites.

Various types of fillers are typically added to polyester and vinyl ester coatings to impart distinct characteristics to the coatings and change specific properties of the coating, such as cost, permeation, abrasion resistance, and flexibility (Table 1).
Common Fillers and Properties Imparted
FillerCoating Properties
Graded & cleaned silicaLow cost, good permeation resistance, good abrasion resistance, reduces thermal expansion, most common filler used
Mineral fillersImproved abrasion resistance, improved fluoride resistance, non-skid; e.g., garnet, anthracite, granite
Carbon fillersElectrical conductivity, fluoride resistance
Carbon fiber veil & weaveFluoride resistance, reduces shrinkage, electrical conductivity
Chopped “C” glass fiberImproved flexural modulus of elasticity, chemical resistance, shock resistance, reduces thermal expansion
Chopped fiberglass matImproved chemical resistance, decreased shrinkage, reduces thermal expansion
Woven fiberglass fabricBidirectional reinforcement, improved strength, reduces thermal expansion
“C” glass veilExcellent chemical resistance, decreased shrinkage, reduces thermal expansion
Ceramic fillersSpecific properties such as lower thermal conductivity, fluoride and alkali resistance, abrasion resistance depending upon the filler (e.g., alumina, silicon carbide, vitreous silica, hollow ceramic and glass beads, etc.)
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你们都看英文的资料了啊,厉害
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只看该作者 板凳  发表于: 2013-12-29
The earliest linings were reinforced with chopped fiberglass or woven roving (woven fiberglass fabric). Later, silica and other mineral fillers were added to improve the release of the heat generated during cure, reduce shrinkage during cure, and reduce the coefficient of thermal expansion (cte) of the coating to better match the cte of the steel or concrete substrate. These earliest linings were either roll-applied or applied by trowel. Later developments included the use of mineral flakes, like mica, and glass flake, which decreased permeation by water vapor and slightly extended the maximum service temperature in wet environments.


Performance Critical Properties

Today’s industries present such diverse chemical and thermal environments that no single resin can withstand the many combinations possible. A variety of resin types is required. The resin chemistry will largely determine how a particular resin behaves in any given chemical/thermal environment. Different resins may well yield widely different results in the same environment. The type of resin chosen will be the principal factor in determining whether a coating will perform as expected.






Flexibility


As noted earlier, vinyl ester and polyester resins are relatively brittle, especially the polyester resins due to the greater number of cross-link sites along the polymer. Unfilled resins generally have a tensile elongation of about 2 to 5%, although some manufacturers offer modified resins with elongations as high 12%. These flexible resins are not as chemical resistant as the unmodified resins, nor do they have the thermal stability or mechanical properties required to function as a topcoat.
Flexibility and elongation properties of these materials are critical to designing a lining system that will not crack in service. It is not as simple as incorporating reinforcement, because reinforcement will reduce elongation capability. Special attention must be paid to areas of high strain, areas where the substrate tends to bend or flex, discontinuities, or localized areas where the temperature on the coating is significantly higher than or lower than the surrounding coating.
The coating manufacturer must be consulted to ensure that the coating has the necessary properties to withstand the intended service conditions.


Tank wall above floating roof before surface prep
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Adhesion
Vinyl ester and polyester coatings have good adhesion to a properly prepared substrate. Both concrete and metallic substrates will require a surface profile to ensure mechanical anchoring so the coating will remain bonded when exposed to the stresses generated during cure and operating conditions. Profile amplitudes, top of peaks to bottom of valleys between peaks, will vary with coating thickness. A minimum profile is about two mils, but can be as high as five mils for very thick liners. Many of these coatings will also use a primer to enhance adhesion.


Chemical Resistance
Because chemical resistance is the most important property for these materials to have, manufacturers spend large amounts of time and money evaluating the resistance of their products to an extremely wide range of chemicals and temperatures. A quick look at the chemical resistance charts that the coating and resin manufacturers publish will reveal hundreds of different chemicals and temperatures in which they have tested their products. Each of the different types of resin has a different resistance to a given chemical environment. There are some generalities that can be made, but there are many exceptions. It is imperative that the user consult the coating or resin manufacturer about each application to ensure that the wrong material is not used.

Bisphenol A epoxy vinyl esters are generally not as chemical resistant as novolac epoxy vinyl esters, but, again, exceptions exist. The novolac vinyl esters are not recommended for calcium or sodium hypochlorite exposure, whereas the bis A vinyl ester is recommended. It must be noted, however, that the bis A vinyl ester must use benzoyl peroxide as the initiator for hypochlorite exposures. MEKP-initiated systems will fail after a relatively brief exposure, especially at temperatures above 100 F (~38 C). Due to the improved chemical and thermal stability imparted to the polymer by the epoxy backbone, vinyl esters generally have better chemical resistance and temperature resistance than polyesters; however, there are several environments where the less expensive polyesters are preferred. The bis A fumarate polyesters exhibit resistance to a wide range of chemicals, including strong alkalies that will attack other polyesters and vinyl esters. Another class of polyesters is the chlorendic polyesters. These chlorinated polyesters have excellent resistance to strong mineral and oxidizing acids, for example, chromic acid. Chlorendic polyesters are the best choice for chromic acid exposures. They are not, however, recommended for alkaline exposures.

Vinyl ester and polyester resins offer resistance to aggressive chemicals at elevated temperatures. In some environments, especially wet ones, these resins can withstand temperatures up to 400 F (204 C), e.g., wet fossil fuel flue gas. As a result, these resins find uses as protective linings for concrete, tanks, secondary containment, flue gas ducts and stacks, floor and wall coatings, structural steel, and process vessels.

Always consult the manufacturer of the coating, because differences in formulations will affect how two coatings made from the same resin will perform. If time permits, ask the manufacturer to prepare cured samples that can be placed in the expected environment for evaluation and testing.

An additional comment is in order regarding chemical resistance charts published by coating and lining manufacturers and resin manufacturers. Most of these tests were conducted according to ASTM test methods, as they should be. However, the ASTM methods are not performance specifications; rather they are detailed instructions on how to conduct the tests. They do not establish pass/fail criteria. The decision as to whether a particular product is recommended for a given environment is left to the individual product manufacturer.

Areas of Concern
There are certain characteristics of polyester and vinyl ester based coatings and linings that require the exercise of caution when using them. One of the primary concerns is the high coefficient of thermal expansion (cte) of both types of resin. Unfilled and unreinforced polyester resins have a cte that is approximately 4 to more than 10 times as great as that of carbon steel and concrete. This large difference will cause problems whenever the temperature changes significantly or too rapidly. Problems could include disbondment, cracking and edge curling. Coating and lining manufacturers are very much aware of this situation and incorporate fillers and reinforcements in their linings and coatings to reduce the cte as much as possible. Fillers like glass fiber, glass flake, and silica have relatively low thermal expansion and are widely used for this purpose, as well as for their reinforcement properties.

Another problem area for these resins is the inherent shrinkage that occurs during cure, which can have undesired effects, such as cracking and disbondment of coatings and delamination in FRP linings shortly after the resin is fully cured.

When curing, these resins are exothermic. The heat developed during cure and the shrinkage occurring at the same time will result in a residual tensile stress that often results in disbondment and cracking. These thermal excursions and volume changes, both from thermal expansion and shrinkage, mandate that linings and coatings be reinforced to prevent premature failure.
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Under floating roof before surface prep
When curing these resins, one must be aware of the inhibiting effect of atmospheric oxygen and excessive atmospheric moisture on cure. Both oxygen and moisture inhibit the cure at the surface where the resin makes contact with the environment. Cross-linking is prevented, leaving a surface that is soft and lacking in chemical resistance. The thinner the coating, the more critical this effect becomes. Different resins are affected to different degrees, but all are affected. To overcome this problem, most coating manufacturers supply a “gel” coat or a specially formulated topcoat that has a small amount of a paraffin wax dissolved in styrene. As the coating or lining begins to cure, the paraffin migrates towards the air side surface. Since it cannot evaporate at ambient conditions, a thin film of paraffin is distributed over the air-exposed surface. The paraffin wax acts as a physical barrier to both oxygen and moisture, thus preventing cure inhibition. The paraffin will be removed by the chemical and/or thermal conditions once the lining is placed into service, leaving a properly cured and fully resistant lining in place.

Polyester and vinyl ester linings and coatings are more sensitive than some other coatings to application conditions. If temperatures are outside of the specified range, cure problems may arise. If the substrate is not properly cleaned, the contaminants may interfere with cure of material adjacent to the substrate. Atmospheric contaminants, too, can interfere with cure. Installers must ensure that all of these potential problems are accounted for during application and approved by the coating manufacturer. These potential problems may require heating the application area and the substrate’s surface; cooling the application area and the substrate’s surface; dehumidifying the application area; or tenting it to protect it from weather, sunlight, and local air pollutants that may otherwise fall onto the substrate and the freshly applied lining/coating.

Start of vinyl ester coating on wall above floating roof

The user should be aware that there will be a small amount of styrene remaining in the cured resin. This will release from the coating/lining over time and if the cured system is smelled close up, the styrene odor will be noticeable for a brief period after cure.

Some applications will require a forced post cure in order to develop full chemical resistance and maximum mechanical properties. If required, a two-hour post cure at 120 F (49 C) is generally sufficient. Consult the coating/lining manufacturer for recommendations.

Polyester and vinyl ester coatings share concerns with other coatings, as well. For example, it is not advisable to apply any coating or lining on concrete or other porous surfaces in direct sunlight or in the presence of soluble salts on the substrate. UV radiation will damage many organic coatings, including polyesters and vinyl esters, causing photo degradation (e.g., chalking of coatings).

Application Methods
For surface preparation, environmental controls, and worker protection, much of what is needed for polyester and vinyl ester linings is needed for their coatings counterparts. But lining application differs from coating application, and each will be discussed separately.

Several types of linings incorporate combinations of trowel-applied protective barriers and some form of fiber glass reinforcement; stand-alone systems also exist.

These materials are aggregate-filled resins designed to be applied by hand trowel or by power trowel. The aggregate can be just about any of those listed in Table 1, or others. Silica is by far the most common filler, but where fluoride resistance is required or where improved abrasion resistance or some other characteristic is needed, other aggregates are used. These systems typically consist of a primer, followed by a trowel-applied layer than can range from ⅛-inch (~3-mm) to as much as ½-inch (~12.5-mm). Over this, one or more layers of a fiberglass fabric or veil may be laid to reinforce the liner. (If fluorides or strong alkalies are expected, either synthetic veil or carbon fiber should be substituted for the fiberglass.) These types of liners are generally used to protect concrete floors. They provide both chemical resistance and excellent mechanical properties, including abrasion resistance.

The fiberglass is then saturated with resin and rolled with a ribbed roller to eliminate air pockets and to ensure that the fiberglass is fully wet with the resin. A final top layer of the trowel-applied material is then applied and sealed with a gel coat. These systems are typically packaged as three-component units. The resin and initiator (MEKP, etc.) are first mixed together thoroughly. Next, the aggregate is mixed until uniformly dampened, at which point the mix is applied.

These same types of linings can be applied by a method called “pour and spread” or “broadcast.” The resin/initiator mixture is spread evenly over the floor with a screed rake to a uniform thickness. The aggregate is immediately spread, or broadcast, over the wet resin, either manually or by mechanical device. The aggregate is broadcast until the aggregate can no longer sink into the resin and the resin can no longer wet the aggregate (“broadcast to excess”). After the resin cures, all loose aggregate is removed with brooms or a shop vac. The surface is then sealed with a liberal coat of resin/initiator, pigmented as desired, and followed by a gel coat. This installation method is faster than troweling, but cannot be used on vertical surfaces and floors with a severe slope. These systems can be applied from 1/16-inch (~1.5-mm) to as thick as ½-inch (~12.5-mm).

Trowel-applied linings may also be filled with silane-treated micaceous iron oxide (MIO) or silane-treated glass flake. Flake-filled liners offer superior permeation resistance. These are usually three-component systems applied by trowel. Immediately after troweling, the surfaces are compacted by rolling with a short nap paint roller to help remove entrapped air near the surface and to help ensure that the flakes are lying flat. The flakes are typically up to ⅛-inch (~3-mm) in diameter. These flakes overlap each other in layers, creating a tortuous path that makes penetration by liquids much more difficult.

Polyester and vinyl ester coatings for industrial applications may be applied by one of two generally preferred spray methods. Both use airless, high-pressure spray equipment to apply the coatings. In one method, called “hot potting,” the resin mixture and initiator are mixed together and then pumped through a material hose to the spray gun. The material is atomized at the spray gun as it is being applied to the substrate. Pressures at the gun tip are typically 5,500 to 6,300 psi.

The second method is plural-component spraying. Plural-component equipment pumps the resin side and the initiator through separate material hoses to the mixing point.

Spray-applied coatings will typically use smaller fillers so they can pass through the spray tip, which can have an opening as small as 0.029 inches (0.74 mm). This includes products made with glass or MIO flake. The flakes in spray-applied coatings do not align themselves parallel to the substrate as uniformly as in the trowel-applied systems but still improve permeation resistance and help provide crack resistance.

Other special fillers may be used, such as carbon for fluoride or alkali service, or glass fiber for flexural modulus and tensile strength improvement, or alumina for abrasion resistance.

Application by spray reduces the overall cost of the installation because the time required to apply the material is typically approximately 10% of the time required to hand apply a liner by trowel.

Because polyester and vinyl ester coatings and linings are relatively brittle, they will break if stretched too much. Thus, when placed over substrates that can move significantly, the coatings will crack. Concrete is famous for its tendency to crack with age. If a brittle coating or liner is placed over concrete that develops a crack, the coating above it will crack as well, a phenomenon called “reflection cracking.” To prevent reflection cracking in the coating, first coat the concrete with a highly flexible coating, such as a flexibilized epoxy, urethane, or rubber, called a crack-bridging membrane. The polyester/vinyl ester coating/liner is then placed over this membrane, which can accommodate the high strains generated by the crack opening as it moves and can thus prevent reflection cracking.

Environmental, Safety, and Health Considerations
Both styrene and cobalt have environmental, health, and safety (EHS) concerns. These concerns mandate that workers take precautions, in accordance with OSHA, EPA, and any other relevant federal, state, or local EHS regulations, when handling polyester and vinyl ester resins. For example, first among these precautions is use of a properly-fitted respirator in compliance with OSHA requirements. OSHA also requires additional protective equipment, including chemical-resistant gloves, face shield or protective goggles, long-sleeved shirt or a full body protective suit, and protective foot gear. If the application is indoors, local ventilation with sufficient capacity to withdraw the styrene vapors is required. All equipment should be electrically grounded to prevent sparking and accidental ignition of the styrene vapors.

The precautions above are not intended to be exhaustive. As with all coatings and linings, always consult the correct Safety Data Sheets (SDS) as well as the appropriate EHS resources (personnel and regulations) before applying polyesters or vinyl esters. Similarly, before you begin the work, take all of the protective measures required. If you become exposed to the product through inhalation, skin contact, or other means, follow all recommended medical procedures.

Summary
Polyester and vinyl ester coatings and linings have a long and successful history of corrosion resistance in a wide range of chemical and thermal environments. They possess high mechanical strength and adhesion as well as low permeation and excellent chemical resistance, even in elevated temperatures. A variety of coatings and linings utilize many different fillers and reinforcements that help impart specific properties. Care must be exercised in using these materials over substrates that move and over concrete that might have, or might develop, cracks. It is strongly recommended that the user consult with the coating/lining manufacturer for each application to ensure that the system will perform as expected and that operating conditions will not result in premature failure. Most important, protection of workers, the public, and the enviornoment must never be ignored.

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只看该作者 5楼 发表于: 2013-12-30
谢谢分享!!

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不过,全英文资料,对坛子里面绝大多数工程界朋友而言,是有一定难度的。不是每一个人都是科班出身的。哪怕就是欧阳本人,看英文资料的速度,远不如中文。英文资料,我还要边看边标记,否则全文理解上,我也不行。
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好东西,都起好费劲!
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只看该作者 8楼 发表于: 2014-01-09
了解基本的耐化学性聚酯和乙烯基酯
加里·霍尔
咨询顾问
加里·霍尔,现已退休,是研发部经理在该公司,公司(匹兹堡,PA)。他是该公司45年。霍尔在NACE,ASTM是积极的,和化学工程师学会。他是一个jpcl特约编辑,也是一jpcl 2012大思想家奖的收件人。
外观邦克原油储罐浮顶。罐的内表面制备随后将乙烯基酯涂料中的应用。
该公司的所有照片由
不饱和聚酯树脂的基础上,马来酸和富马酸已自20世纪20年代以来众所周知的。在20世纪30年代末,这些树脂的现代形式介绍了当查尔顿埃利斯结合苯乙烯与不饱和聚酯。
聚酯和乙烯基酯树脂已被用于在恶劣的化学环境50年在砂浆形成耐化学砖和玻璃纤维增强塑料(FRP)。这些成功的基于LED提供优越的耐广泛的化学品,这些树脂的耐化学腐蚀涂层和衬里的发展,特别是酸的,并且比大多数其他类型的环氧树脂和聚氨酯涂层的温度高1
术语“涂料”、“衬里”是本文中使用的。为本条的目的,衬板是由玻璃纤维毡,方格布,或饱和树脂的选择。它们适用于玻璃纤维加固饱和树脂片,然后放在基板和卷的地方使用网纹辊。涂料通常比薄衬和用于刷辊,无气喷涂,混合,和多组分喷射。
本文介绍了聚酯和乙烯基酯,基本的化学性质,与材料的关系,以及应用方法。
基础化学
不饱和聚酯树脂是由二元有机酸反应形成,如邻苯二甲酸、马来酸,和醇或多元醇如乙二醇。不饱和聚酯树脂(通常称为“树脂”或“聚酯”)是一种热固性可以治愈从液体状态,在适当的条件下。广泛的聚酯,包括部分芳香族和芳香的版本,可以通过使用不同的酸,使甘醇,醇,和单体,每个都有不同的属性(图1)。
用于涂料聚酯树脂通常是浅色的,粘稠的液体组成的聚酯溶解在苯乙烯单体,通常。苯乙烯降低树脂的粘度,使它更容易处理。苯乙烯是称为活性稀释剂,因为它涉及的聚酯树脂的固化,以及降低粘度。他们的治疗是通过自由基机理。自由基是由有机过氧化物反应产生,如过氧化甲乙酮(MEKP),和还原剂,一个典型的钴盐。这种类型的自由基引发被称为氧化还原(氧化还原)反应。当添加到树脂,的MEKP分裂成两个自由基[ RO•+房间•],其中每个然后与苯乙烯的反应,使其形成一个新的自由基。
这些苯乙烯基反应后再与碳碳双键(C = C)相邻的酯基团的聚酯树脂分子形成相邻的聚合物分子之间的交叉链接的长度,而不产生副产物。未固化的聚酯分子具有多个反应位点沿分子的长度。多重交叉链接网站确保分子紧密贴合的。这允许高机械强度和优异的耐化学性,但它也介绍了刚度对交联网络。这不可逆反应在一个密集的、复杂的网络相互交织的聚合物具有良好的耐化学性的结果。聚酯树脂和乙烯基酯树脂反应活性很高,有一个短的保质期,并将凝胶或自行设定在站。高温加速这个反应。抑制剂通常制造延长贮存寿命期间加入。制冷也经常建议。即使有抑制剂和制冷的使用,聚酯和乙烯基酯树脂的保质期通常是三个月或以下。
饱和二羧酸的酸是用聚酯控制交联密度和优化的固化的聚合物网络的性能。三种最常用的二羧酸的酸及其在固化网络的贡献是在36页所示的框。
制定的乙烯基酯和聚酯涂料,涂料制造商将加入其他的材料,包括引发剂;促进剂;和典型的涂层材料如thixotropes,填料,颜料。玻璃鳞片和硅烷处理过的云母氧化铁(MIO)往往是首选的填料,因为
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欧阳 小红花 +1 只能说鼓励你的积极性!但不宣扬你这样翻译软件翻译出来,没有任何条理性的杂乱无章的文字。 2014-01-09
欧阳 绿叶 +1 只能说鼓励你的积极性!但不宣扬你这样翻译软件翻译出来,没有任何条理性的杂乱无章的文字。 2014-01-09
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只看该作者 9楼 发表于: 2014-01-09
在浮顶前的表面准备
这些树脂固化时,必须考虑大气中的氧和大气水分过度治疗的抑制作用。氧气和水分的抑制在表面上的树脂与环境接触治疗。防止交叉连接,留下一个表面,耐化学性是软的,缺乏的。涂层越薄,更关键的这种效应就。不同树脂受到不同程度的影响,但受影响。为了克服这个问题,大多数涂料制造商提供一个“凝胶”的外衣或特制的面漆,有少量的石蜡溶解在苯乙烯。作为涂层或李宁开始治疗,石蜡向空气侧表面。因为它不能蒸发,在室温条件下,薄膜的石蜡分散在空气中暴露的表面。石蜡作为氧气和水分的物理屏障,从而防止治疗抑制。石蜡将被删除的化学和/或热条件一旦李宁投入服务,留下一个适当的养护和完全的耐药性李宁的地方。
聚酯和乙烯基酯衬里和涂层的应用条件比其他镀层更敏感。如果温度是指定的范围之外,治疗可能出现的问题。如果基板是不清洁的,污染物可能会干扰到相邻的衬底材料固化。大气污染物,也会干扰治疗。安装程序必须保证所有这些潜在的问题占在应用和涂料生产商的批准。这些潜在的问题可能需要加热的应用领域和衬底的表面;冷却的应用领域和衬底的表面;除湿应用领域;或露营来保护它免受天气,阳光,和当地的空气污染物,否则可能落在基板和新应用的李宁/涂层。
乙烯基酯涂层在墙上面浮顶开始
用户应该知道,会有少量苯乙烯残留在固化树脂。这将从涂层/李宁随着时间的推移,如果固化系统是闻到了关闭释放,苯乙烯气味会引人注目,在短时间内治愈后。
一些应用程序需要将强制治愈后为了充分的耐化学性和最大的机械性能。如果需要,在120小时后固化F(49 C)通常是足够的。咨询涂层/李宁制造商的建议。
聚酯和乙烯基酯涂料的关注份额与其他涂料,以及。例如,应适用于在阳光直接照射或可溶性盐对底物存在下的混凝土或其他多孔表面的任何涂层或李宁是不。紫外线辐射会伤害许多有机涂料,包括聚酯和乙烯基酯,造成光降解(例如,粉化的涂料)。
应用方法
表面处理,环境控制,工人的保护,什么是聚酯和乙烯基酯衬里需要的是他们的同行所需要的涂料。但李宁应用不同于涂料中的应用,每个将另行讨论。
用几种类型包括抹子应用保护屏障和某种形式的玻璃纤维增强的组合;独立的系统也存在。
这些材料是骨料填充树脂的设计是用手抹或用动力工具的应用。集合可以是那些在表1中列出,或其他。硅是目前最常用的填料,但在抗氟性是必需的或改进的耐磨性或其他一些特性是必要的,使用其他聚合。这些系统通常包括一个引物,其次是应用层泥铲比的范围可以从⅛英寸(~ 3mm)尽½英寸(~ 12.5毫米)。在这,一层或多层玻璃纤维织物或面纱可能把加强衬。(如果氟化物或强碱预计,无论是合成的面纱或碳纤维可以代替玻璃。)这些类型的内衬一般是用来保护混凝土地板。他们提供的耐化学性和优良的机械性能,如耐磨性。
玻璃纤维是饱和树脂和冷轧带肋辊消除空气的口袋,并确保充分湿玻璃纤维与树脂。最后一层抹灰应用材料分别应用与凝胶涂层密封。这些系统通常被封装为三单元。树脂、引发剂(过氧化甲乙酮,等)是第一个混合在一起,彻底。接下来,骨料混合至均匀了,此时的组合应用。
这些类型的内衬可以采用一种称为“倒和传播”或“广播”

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只看该作者 10楼 发表于: 2014-01-09
只能说鼓励你的积极性!但不宣扬你这样翻译软件翻译出来,没有任何条理性的杂乱无章的文字。

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只看该作者 11楼 发表于: 2014-01-09
这种英文,是需要专业英文的功底的,要是了解本身这方面的技术,当然更好
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只看该作者 12楼 发表于: 2019-05-15
告辞!

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只看该作者 13楼 发表于: 2019-05-15
一头雾水!还是看看欧阳的《乙烯基树脂及其应用》过瘾,如果会翻译加专业技术,那就锦上添花了,可惜本人英文水平不好,看起来要理解半天,希望本站能够多一些防腐蚀技术翻译大咖,分享国外的同行经验,那真是功德无量。
做一个能干能写的防腐蚀老兵(30多年的防腐蚀施工)