Chemical resistance epoxy

Because of the low shrinkage and the excellent adhesion, mechanical properties, and chemical resistance, epoxies have a vast variety of applications, such as adhesives (epoxyamine), structural materials in high-performance composites (epoxy-amine) (e.g., aircraft primary structure), filament wound pressure vessels, and so forth. The main disadvantage of... 

There are several ways by which the formulator can moderately improve the heat or chemical resistance of room temperature curing epoxy adhesives. Using an elevated-temperature cure or a postcure will, of course, improve the temperature resistance by virtue of improved crosslink density. However, this section describes formulations that have been developed for moderately improved heat resistance after only a cure at room temperature. Optimal (heat-curing) high-temperature and chemically resistant epoxy adhesives are discussed in Chap. 15. 

The presence of reactive sites such as double bonds, hydroxyl and carboxyl groups and phenyl rings in aromatic anhydride and ester linkages all provide tremendous potential for the modification of oil-modified polyester. Epoxy resins are considered to be polyols, which react with the carboxylic functions of polyester resin. The modification of oil-modified polyesters with epoxy resins results in products with excellent adhesion properties and improved water and chemical resistance. Epoxy modified polyesters are less expensive than epoxy resins. 

These adhesives are products of reachon between an epoxy resin and liquid polysulfide polymer, usually catalyzed by an additional tertiary amine.They are available as two-part liquids or pastes that are usually cured at room or higher temperatures to rubbery solids that provide bonds with excellent flexibility and chemical resistance. Epoxy-polysulfide adhesive forms satisfactory bonds to different substrates. Shear strength and elevated-temperature properties are low, but resistance to peel and low temperature is acceptable. ... 

A Clear and rigid, unfilled room temperature cure, tough, strong, good heat distortion temperature and chemical resistant, epoxy laminating resin, a. 1.16 i. 190 C k. 265 m. 12.7... 

AR-Lon 6100. FDA and USDA excepted, the properties of AR-Lon 6100 markedly improve abrasion resistance and product fiow. The chemically resistant epoxy primer has excellent adhesion and fiexibility. The super-slick properties of polytef are combined with a urethane topcoat that provides additional impact protection and abrasion resistance. It is baked on at over 200°F (93°C). 

Chemical resistant epoxy vinyl ester resins serve the needs of a wide range of process in sulfur acid production at petrochemical enterprises with final FRP products, such as chimney liner, process pipes, ducts and scrubbers such as chimney liner, process pipes, ducts and scrubbers [1]. 

Bisphenol A. One mole of acetone condenses with two moles of phenol to form bisphenol A [80-05-07] which is used mainly in the production of polycarbonate and epoxy resins. Polycarbonates (qv) are high strength plastics used widely in automotive appHcations and appHances, multilayer containers, and housing appHcations. Epoxy resins (qv) are used in fiber-reinforced larninates, for encapsulating electronic components, and in advanced composites for aircraft—aerospace and automotive appHcations. Bisphenol A is also used for the production of corrosion- and chemical-resistant polyester resins, polysulfone resins, polyetherimide resins, and polyarylate resins. 

Epoxy phenoHc coatings either are made by blending of a soHd epoxy resin with a phenoHc resin or are the products of the precondensation of a mixture of two resins. A three-dimensional stmcture is formed during curing which combines the good adhesion properties of the epoxy resin with the high chemical resistance properties of the phenoHc resin. The balanced properties of epoxy phenoHc coatings have made them almost universal in their appHcation on food cans. 

The outstanding performance characteristics of the resins are conveyed by the bisphenol A moiety (toughness, rigidity, and elevated temperature performance), the ether linkages (chemical resistance), and the hydroxyl and epoxy groups (adhesive properties and formulation latitude, or reactivity with a wide variety of chemical curing agents) (see also Phenolic resins). 

The bisphenol A-derived epoxy resins are most frequendy cured with anhydrides, aUphatic amines, or polyamides, depending on desired end properties. Some of the outstanding properties are superior electrical properties, chemical resistance, heat resistance, and adhesion. Conventional epoxy resins range from low viscosity Hquids to soHd resins. 

Owing to relatively low viscosity, these resins offer advantages for 100% soHds (solvent-free) systems. Higher filler levels are possible because of the low viscosity. Faster bubble release is also achieved. Higher epoxy content and functionaHty of bisphenol F epoxy resins can provide improved chemical resistance compared to conventional epoxies. 

The multiepoxy functionality of the epoxy novolaks (2.2 to >5 epoxy groups per molecule) (3) produce more tightly cross-linked cured systems having improved elevated temperature performance and chemical resistance than the difunctional bisphenol A-based resins. 

The thermal stabiUty of epoxy phenol—novolak resins is useful in adhesives, stmctural and electrical laminates, coatings, castings, and encapsulations for elevated temperature service (Table 3). Filament-wound pipe and storage tanks, liners for pumps and other chemical process equipment, and corrosion-resistant coatings are typical appHcations using the chemically resistant properties of epoxy novolak resins. 

Polynuclear Phenol—Glycidyl Ether-Derived Resins. This is one of the first commercially available polyfunctional products. Its polyfunctionahty permits upgrading of thermal stabiUty, chemical resistance, and electrical and mechanical properties of bisphenol A—epoxy systems. It is used in mol ding compounds and adhesives. 

Powder Costings. Epoxy-based powder coatings exhibit useful properties such as exceUent adhesion, abrasion resistance, hardness, and chemical resistance. The appHcation possibUities are diverse, including refrigerator liners, oU filters, hospital equipment, primers, shelving, automobUe springs, and fire extinguishers. 

Structural Composites. Because of their exceUent adhesion, good mechanical, humidity, and chemical-resistance properties, epoxy resins are... 

Meta-phenylenediamine, a crystalline solid with a melting point of about 60°C, gives cured resins with a heat distortion temperature of 150°C and very good chemical resistance. It has a pot life of six hours for a 200 g batch at room temperature whilst complete cures require cure times of four to six hours at 150°C. About 14 pts phr are used with the liquid epoxies. The main disadvantages are the need to heat the components in order to mix them, the irritating nature of the amine and persistent yellow staining that can occur on skin and clothing. The hardener finds use in the manufacture of chemical-resistant laminates. 

Elevated temperatures are necessary for cure and the chemical resistance of the laminates is inferior to those from unmodified resins. Because of problems in handling, the polyamides have found only limited use with epoxy resins, mainly for coating and adhesive applications. 

Epoxy hardener will strongly affect chemical resistance. 

Epoxy resin paints, inferior to chlorinated rubber for resistance to strong acids, are excellent for dilute acids and strong alkalis. They produce a harder, more abrasion-resistant coating than does chlorinated rubber and are much better for resistance to fats, oils and many organic solvents. Table 3.50 gives data on the chemical resistance of epoxy resin coatings to different materials. 

Tabic 3.50. Chemical Resistance of Epoxy Resin Coatings [54]... 

Major uses of epoxy resins are coatings for appliance finishes, auto primers, adhesive, and in coatings for cans and drums. Interior coatings of drums used for chemicals and solvents manifests its chemical resistance. 

Two-component epoxy resin water thinned dispersions are now being used as floor sealers. They have good adhesion to concrete as well as good chemical resistance. However, the particle size of the dispersion is comparatively large (approximately 1-1.5 microns) and consequently penetration into good-quality concrete is minimal and an on-surface seal is obtained. However, with porous low-quality concrete substances, considerable binding/strengthening, etc. of the surface can be achieved with water-dispersible epoxy resin-based floor sealer. 

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