Polyesters also corrosion resistance

Isophthalic polyesters provide corrosion resistance in a wide variety of end uses. Recent excavations of 25-year-old FRP underground gasoline storage tanks offer evidence to the resin s resistance to internal chemical attack or external attack by water in the siuroimding soil. Isopolyester pipes and containment vaults also provide protection against failme from corrosion by acid media. Reference [2] provides information on FRP piping systems. 

In the early 1990s, at Newtown Square in Pennsylvania, Lyondell Chemical Company developed an interesting alternative to produce unsaturated polyesters. Based on this development, it became possible to produce a series of very flexible UPRs without sacrificing either mechanical or thermal properties. These products also showed good corrosion resistance when compared to conventional UPR resins. 

Velsicol Chemical LLC, formerly Velsicol Chemical Corporation, designs, manufactures, markets and distributes high performance specialty chemicals and industrial intermediates, primarily based on benzoic acid and the organic compound cyclopentadiene. Its products include chlorendic anhydride and hexachlorocyclopentadiene (HEX). Chlorendic anhydride is corrosion resistant, fire resistant and has high UV stability, and is used in the synthesis of flame retardant polymers such as polyurethanes, unsaturated polyester and epoxy resins. HEX, a reactive intermediate used in the manufacture of agricultural pesticides in the production of flame retardants for the wire and cable industry and in the preparation of chlorendic anhydride. The company s products are produced primarily at a plant in Memphis, Tennessee Velsicol also maintains the Memphis Environmental Center (MEC), which focuses on managing legacy environmental liabilities. The firm is owned by Arsenal Capital Partners, a private equity firm. 

Of finishes used outside, the polymers that can offer the best protection against acid deposition are those not containing acid-sensitive groups such as esters. Inclusion of acid resistant paint binders such as vinyls, urethane, and epoxies would produce acid resistance only if the other components are also acid resistant. Saponification of esters catalyzed by hydroxyls formed during corrosion of steel substrates may also degrade polyesters (7). 

In industrial filtration a common filter medium is canvas cloth, either duck or twill weave. Many different weights and patterns of weave are available for different services. Corrosive liquids require the use of other filter media, such as woolen cloth, metal cloth of monel or stainless steel, glass cloth, or paper. Synthetic fabrics like nylon, polypropylene, and various polyesters are also highly resistant chemically. 

In common with most plastics, polyester resins have good all-roimd resistance to chemical attack and corrosion, but all significant conditions must be known before a particular resin is specified. Improved corrosion-resistance is usually based on iso- or terephthalic acid and neopentyl glycol, giving good mechanical properties. These resins are also suitable for gel coats that are continuously stressed with warm water (such as... 

Halogenated resins consist of chlorinated or brominated polymers. The chlorinated polyester resins ciured at room temperature and reinforced with fiberglass possess unique physical, mechanical, and corrosion resistance properties. These are also known as chlorendic polyesters. 

Reinforced polyesters have been widely used in the boat building industry since the early sixties. Most yachts and power boats are now made of polyester resins and glass fibre. Reinforced polyester plastics are also widely used in pipe and container structures, owing to their good chemical and corrosion resistance. Polyesters have increased their role in vehicle and transportation equipment production, where many parts previously manufactured from metal have been replaced with components produced from reinforced plastics. 

The most common diacids are the phthalic acids, orthophthalic acid (phthalic anhydride is actually used) giving general purpose resins and isophthalic acid giving resins of improved corrosion resistance. Adipic acid is also used, but on a smaller scale and where chain flexibility is particularly required. The most commonly used glycol is propylene glycol because it does not lead to branching in the polyester chain and has no tendency to crystallise. Other diols are used to achieve special properties, e.g., propoxylated bis-phenols to confer corrosion resistance. Typically, the resin would incorporate the three components in the molar ratio, maleic anhydride phthalic anhydride propylene glycol (5 5 11). 

A special blend of polymers that produces an air-cure film which bonds polyester resins and coatings to epoxy resins and coatings. Can be spray, brush or roller applied. Also excellent for use as an air-cure coating for corrosion-resistant air-inhibited systems. 

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