Polyesters also chemical resistance

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. 

CPA. Copolymer alloy membranes (CPAs) are made by alloying high molecular weight polymeries, plasticizers, special stabilizers, biocides, and antioxidants with poly(vinyl chloride) (PVC). The membrane is typically reinforced with polyester and comes in finished thicknesses of 0.75—1.5 mm and widths of 1.5—1.8 m. The primary installation method is mechanically fastened, but some fully adhered systems are also possible. The CPA membranes can exhibit long-term flexibiHty by alleviating migration of the polymeric plasticizers, and are chemically resistant and compatible with many oils and greases, animal fats, asphalt, and coal-tar pitch. The physical characteristics of a CPA membrane have been described (15). 

The chemical resistance of polyester materials is well recognised to be limited because of the comparative ease of hydrolysis of the ester groups. Whereas this ease of hydrolysis was also observed in aliphatic polycarbonates produced by... 

Laminates have been prepared for the manufacture of chemical plant. They have better heat and chemical resistance than the polyester- epoxide- phenolic- or aminoplastic-based laminates but because of the low viscosity of the resins were not easy to handle. Because they were also somewhat brittle, furan-based laminates have been limited in their applications. 

GE introduced, in 2000, a new polyester carbonate based on resorcinol arylates called W-4. It is now marketed as Sollx. Sollx does not need to be painted, it offers good weather, chip, scratch, and chemical resistance and is being used as the fenders for the new Segway Human Transporter. It is also aimed at automotive uses including body panels. Sollx is coextruded into two layers clear and colored, to simulate automotive paint. It is then thermoformed and molded into the finished product. 

Chrome yellow pigments stabilized with a large amount of silicate play a major role in the production of colored plastics (e.g., PVC, polyethylene, or polyesters) with high temperature resistance. Incorporation into plastics also improves their chemical resistance to alkali, acid, sulfur dioxide, and hydrogen sulfide. 

Saran (Dow polyvinylidene dichloride) is a tough, chemically resistant plastic available in a variety of forms that are useful in the laboratory. Saran pipe or tubing can easily be welded to itself or sealed to glass and is useful for handling corrosive solutions. Thin Saran film, available commercially as a packaging material, is useful for windows, support films, etc. Mylar (du Pont polyethylene terephthalate) film and other polyester films are also useful for these purposes. Mylar is chemically inert and has excellent electrical properties for electrical insulation and for use as a dielectric medium in capacitors. Much thinner than these are films that can be made in the laboratory by allowing a dilute ethylene dichloride solution of Formvar (polyvinyl acetal) to spread on a water surface and dry. 

This type of lining was originally designed for the repair of sanitary services, and the first resins used belonged to the terephthalate polyester class. Interest at once centered on repairs to industrial waste lines and in some cases, it was obvious that better chemical resistance was required than that offered by this resin type. Although considerably more expensive, this same general system, but employing epoxy resins, is now also available. Of course, neither type resin is suitable for all waste exposures. 

Polymer concretes show excellent mechanical properties and chemical resistance compared with conventional cement concretes. Polymer concretes can be cured quickly by the use of curing agents. Thus, the applications of polymer concretes are being increased. One of the popular polymers for polymer concretes is unsaturated polyester (UPE) resin. The properties of UPE resin can be modified by changing its molecular features. For the synthesis of the resin, phthalic anhydride or isophthalic acid as well as maleic anhydride can be employed to modify the mechanical properties or hydrothermal resistance. Terephthalic acid which is also used for the synthesis of poly ethylene terephthalate (PET) enhances the thermal resistance of the cured UPE resin. However, the synthesis of unsaturated polyester resin from terephthalic acid is difficult. One method to synthesize unsaturated polyester from terephthalic acid is the use of recycled PET. 

The classic thermosets, such as ebonite, phenolics, ureas, melamines and polyesters as well as the epoxies, when reinforced with fiberglass or graphite fibers could also be classified as high performance thermosets. While these plastics cannot be readily extruded or injection molded, they are resistant to the effects of moderately high hostile environments. Phenolic resin mortars have been used for over a half century for the construction of chemical resistant vessels and for joining brick and tile used as linings in hot acid environments. (1.)... 

Choice of the fabric, i.e., polypropylene, polyester, nylon, etc., is dependent upon the resistance of the cloth to the solvent and wash liquor used. Chemical resistance charts should be referenced to choose the most suitable fabric. The temperature of the filtration must also be considered. 

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. 

Molten polyesters show low viscosity and small extmdate swell. For these reasons, they have been blended with amorphous polymers to improve the latter s processability and chemical resistance. Elastomers have also been added to polyesters to improve impact resistance. Blends of polyester (either PET or PBT) with polycarbonate, PC, are the most popular (viz., Bay/oF, BCT4201, Calibre , Dialoy P, Ektar MB (with PCTG), Idemitsu SC, MakroblencT, MB4300, NovadoF, Pocan , R2-9000, Sabre , SC 600, Stapron E, Ultra-blencF KR, Valox , Xenoy 1000, etc.). Presence of PC in PET/PC increases crystallization rate of PET, which translates into faster injection molding cycle and lower part distortion upon demolding than those observed for neat PET. 

The thermoplastic polyesters have been often blended with amorphous polymers to improve chemical resistance and processability. Elastomers have also been added to improve their impact resistance. 

Polyester mortars are used in oxidizing services such as nitric and chromic acid. They are, however, more expensive than furan and also exhibit a narrower range of chemical resistance. They are usually a three-component system consisting of a resin, a powder, and a curing agent. 

Electrical tapes or insulating tapes require adhesives that will not corrode wiring, joints, or components. They should resist deterioration resulting from age and exposure to heat. Occasionally, chemical resistance may also be required. PVC is still the most widely used backing, but other films, espedally polyester, are increasing in use. Rubber- or elastomer-based adhesives are suitable for service up to 130°C, acrylics to 155°C, while silicones, preferably on PTFE, can be used up to 180°C. 

The term TS polyester covers a very large chemical family, of which the unsaturated resins (covering orthophthalic, isophthalic, vinyl esters, and blends) form the largest single group of fiber reinforced TSs (RTSs). Polyesters offer a good balance of mechanical, electrical and chemical-resistance properties, at relatively low cost (Table 3.15). They also have good dimensional stability and are relatively easy to handle. They are... 

The standard corrosion grade isophthalic polyesters are made with 1 1 molar ratio of isophthalic acid to maleic anhydride or fumaric acid with propylene glycol. In general, the properties of isophthalic polyesters are superior to the lower-cost general purpose polyesters, not only in chemical resistance but also in physical properties. They can be formulated to be fire retardant or to protect against the effects of ultraviolet light. 

---