Speciality thermoset resins

Prestressed-brick linings can be used to protect the outer shell. In this case, the bricks are installed with a special thermosetting-resin mortar. After lining, the vessel is subjected to internal pressure and heat. This expands the steel vessel shell, and the mortar expands to take up the space. The pressure and temperature must be at least as high as the maximum that will be encountered in service. After the mortar has set, reduction of pressure and temperature will allow the vessel to contract, putting the brick in compression. The upper tem-... 

Molds and forms used for advanced FRP febrica-tions are constructed from specialized materials that closely match the thermal responses of the materials being molded and are typically custom-machined with exacting precision. Highly specialized thermosetting resins and advanced reinforcement materials such as... 

A variety of thermosetting resins are used in SMC. Polyesters represent the most volume and are available in systems that provide low shrinkage and low surface profile by means of special additives. Class A automotive surface requirements have resulted in the development of sophisticated systems that commercially produce auto body panels that can be taken direcdy from the mold and processed through standard automotive painting systems, without additional surface finishing. Vinyl ester and epoxy resins (qv) are also used in SMC for more stmcturaHy demanding appHcations. 

Thermoset resins covers an extremely wide range, including phenol formaldehyde polymers, aminopolymers, PUs, epoxies, and thermoset polyesters, which include the alkyd and unsaturated vinyl ester resins. Of special interest at the present time are those that comprise the resin component of liber-reinforced composites that are finding increasing use in commercial and defense sectors, where fire resistance is of paramount importance. Typical resins used are those listed in Table 2.4 along with typical, respective LOI values in descending order of increased inherent fire resistance. 

The decorative laminates described in the previous chapter are made with selected thermosetting resins while resins of this type can be moulded and extruded by methods similar to those outlined in the present and the next chapter the materials employed for these processes predominantly are thermoplastic. Many such plastics can be moulded and extruded under suitable conditions, the most important in terms of quantities used being those that combine properties satisfactory for the purpose with convenience in pro-cessing-especially the polyolefins (polyethylene and polypropylene), poly(vinyl chloride), and styrene polymers and blends. Other plastics with special qualities, such as better resistance to chemical attack, heat, impact, and wear, also are used—including acetals (polyformaldehyde or polyoxymethylene), polyamides, polycarbonates, thermoplastic polyesters like poly(ethylene terephtha-late) and poly(butylene terephthalate), and modified poly(phenylene oxide),... 

A special group of thermosetting resins prepared from polyhydric alcohols and polybasic acid or anhydrides - used mainly as lacquers. 

Most high performance applications in aircraft use epoxy-based resin systems. Silicones, phenolics and polyimides are limited to special high temperature or electrical applications. Although thermosetting resins such as epoxy are commonly used in filament winding, there has been recent research into using thermoplastic matrix materials [9]. 

The major thermosetting plastics, in order of decreasing market volume, are polyurethanes, phenol-formaldehyde, urea-formaldehyde, and polyesters. More specialized thermosets include melamine-formaldehyde, furans, vinyl esters, aUyls, epoxy resins, silicones, and polyimides. While they may sometimes compete with each other and with thermoplastics, for the most part, each of them has unique properties and fills unique markets and applications. 

Gas-injection molding n. A specialized technique for molding low-density structures in which a mixture containing cork particles, or glass or phenolic microspheres, glass fibers, and a thermosetting resin is injected into a mold by fluidizing it in a gas stream. 

Infusible ( )in- fyu-z9-b9l (1555) adj. Not capable of melting when heated, as are all cured thermosetting resins and a few special thermoplastics such as ultrahigh-molecular-weight polyethylene, polybenzimidazole, and aramid resins. 

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