Cast phenolic resins

TABLE 2.14 Properties of Cured Cast-Phenolic Resins... 

Steel castings have been declining while non-ferrous castings, mainly aluminum base, are gaining. The automotive industry is the major user of castings. Phenolic resins are the most common type of binder utilized (Table 32). 

It is likely that the quinone methide and related structures formed at these temperatures account for the dark colour of phenolic compression mouldings. It is to be noted that cast phenol-formaldehyde resins, which are hardened at much... 

The rotor (forged steel) may or may not be an integral part of the shaft. In any case the material for both rotor and shaft is usually a high-strength alloy cast iron. The rotor has radial slots machined along its entire length. The blades or vanes are of heat-treated phenolic resin, metal, or suitable material to withstand the gas and the pressure fit in these slots. 

Abrasion-resistant white cast irons, molybdenum in, 17 17 Abrasive Grain Association (AGA), silicon carbide standards by, 22 537, 538 Abrasive materials, phenolic resins in,... 

Finally, metal- and resin-bonded composites are also classified as particulate composites. Metal-bonded composites included structural parts, electrical contact materials, metal-cutting tools, and magnet materials and are formed by incorporating metallic or ceramic particulates such as WC, TiC, W, or Mo in metal matrixes through traditional powder metallurgical or casting techniques. Resin-bonded composites are composed of particulate fillers such as silica flour, wood flour, mica, or glass spheres in phenol-formaldehyde (Bakelite), epoxy, polyester, or thermoplastic matrixes. 

Cured phenolic resins have outstanding heat resistance, resistance to cold flow, good electric (insulation) properties, and good dimensional stability. Phenolic resins have good adhesive properties and are employed in the production of sandpaper, abrasive wheels, and brake linings. These resins are also used as casting resins. 

Superior toughness and mechanical properties The strength of properly formulated epoxy resins usually surpasses other types of casting resins. The cured epoxy resins [Structure (4.35)] are seven times tougher than the cured phenolic resins [Structure (4.36)] as is evident from Figure 4.15. The relative toughness is attributed to the distance between the crosslinking sites and presence of internal aliphatic chains. 

CA 73, 27154x (1970) (Cast expl charge contg air-filled phenolic resin microspheres or cork flour in various proportions to permit the selection of the deton rate. An adhesive or a hinder may he added)... 

A new approach was proposed for making effective helmets which could replace the former British army steel helmet. Essentially the new helmet used modified phenolic resins reinforced with nylon, and the crown cap inside was thermoformed from polyethylene. Formerly the crown cap was attached to the steel by rivets—not an appropriate method for fixing polyethylene to reinforced plastics. Instead a method was developed with a hot-melt adhesive based on ethylene-vinyl acetate copolymers cast as film on release paper. For assembly, the cast film is cut in advance to match the intricate shape required and activated by heat to bond under light pressure subsequently, a further heat activation is employed to fix the crown cap in place (Figure 52 illustrates this). 

Shell mold casting, which uses molds that are thin shells of sand bonded with a thermosetting phenolic resin. The shell is removed from the pattern and baked at 300--400°F (147-202°C) to completely set the resius. Finally the shells are assembled to complete the mold. 

Wijdenes and Geomini (170) examined the effects of the phenolic resin composition, its molecular weight distribution, solvent composition, and prebake temperature on the interfacial layer formation. They found that combined use of poly(p-vinylphenol) (structure 3.10) as matrix resin and cyclohexanone as the casting solvent in the diazoquinone resist formulation minimizes mixing of the two layers and yields a capped PCM structure without any plasma treatment. 

Phenolic and Other Tar Acid Resins Casting. Phenolic and other tar acid resins for casting are disclosed from 1934 to 1937, and phenol-formaldehyde for casting is disclosed from 1938 to 1941 and for 1943 (11). 

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