Thermosets casting resins

Casting is, of course, possible when the material is fluid enough. This is the case with some thermosets (casting resins), which, together with a second component, can be cast into a mould and then cured at a higher temperature. 

Plastic, rubber, and non-iron metal processing (extrusion aid and release additive for plastics and rubber e.g., PUR, thermosets, casting resins, high melting point mold release agents and additives)... 

For prototyping or for limited production runs, liquid resin casting offers simplicity of process, relatively low investment in equipment, and fast results. Thermoset casting resins may be epoxies, polyesters, phenolics, etc. The resins harden by a polymerization or cross-linking reaction. Such resins are often poured into open molds or cavities. Because pouring is done at atmospheric pressure, molds are simple, often made of soft metals (Fig. 6.2). 

The commercial possibiUties for epoxy resins were first recognized by DeTrey Emres in Switzerland and DeVoe and Raynolds in the United States (1,2). In 1936, DeTrey Emres produced a low melting bisphenol A-based epoxy resin that gave a thermoset composition with phthaUc anhydride. Apphcation of the hardened composition was foreseen in dental products, but initial attempts to market the resin were unsuccessful. The patents were hcensed to CIBA AG of Basel, Switzerland (now CIBA-GEIGY), and in 1946 the first epoxy adhesive was shown at the Swiss Industries Eair and samples of casting resin were offered to the electrical industry. 

Casting resin ( monomer ) with no added peroxide hardener (free radical initiator) does not polymerize at any appreciable rate. Increasing the concentration of hardener should increase the rate of polymerization but not change the properties of the final cured resin. Increasing the temperature should increase the rates of initiation and polymerization. Polystyrene is a linear thermoplastic that dissolves in acetone. The cured casting resin is an extensively crosslinked thermoset material that is insoluble in everything. 

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. 

Atlac . [Reichhold/Reactive Polymers] Thermoset polyester resins for fiberglass-reinforced structures, glass-reinforced coatings, mortars in pulp and paper, caustic-chlorine, metal treatment, filament winding, centrifugal casting of large tanks and pipe. 

Polylite . [Reichhold ReichhoIdChemie AG] Thermoset polyester resins cast-ing resin producing a Corian lode-alike prod. 

Chem. Descrip. Aluminum hydroxide CAS 21645-51-2 EINECS/ELINCS 244-492-7 Uses Filler, flame retardant for thermoset plastics, polyester (concrete, artificial marble), epoxy casting resins, crosslinked elastomer cables, carpetbacking latexes, urea/phenolic chipboard, paints, varnishes... 

The materials in this group are linear copolyesters. One of the dicarboxylic acids is an aliphatic unsaturated diacid. The unsaturation is introduced into the polymer backbone for the purpose of subsequent crosslinking. Unsaturated polyester technology was developed for use in glass fiber laminates, thermosetting molding compositions, casting resins, and solventless lacquers. 

Other differences, both in kind and degree, combine to make the thermosetting resins as a class useful in many industrial applications for which the thermoplastics are chemically unsuited. The thermosetting epoxy resins possess a number of unusually valuable properties immediately amenable to use in the formulation of adhesives, sealing liquids, cold solders, castings, laminates, and coatings. The more important of these properties include ... 

ABS Resins Molded, Extruded Medium impact Phenolics High Shock Chopped Fabric or Cord Filled Phenolics Molded General Woodflour and Flock Filled Polyester, Thermoset Cast Rigid 0.08—0.18 0.097—0.170 0.097—0.3 0.10—0.12... 

Olefin Copolymers Molded EVA (ethylene vinyl acetate) Olefin Copolymers Molded lonomer ABS Resins Molded, Extruded Medium impact Polyester Thermosets Cast Rigid 0.003 0.003 0.003—0.006 0.003—0.04... 

Diallyl Phthalate n (diallyl o-phthalate, DAP). In the monomeric form, DAP is a colorless liquid ester with a viscosity about equal to that of kerosene, widely used as a crosslinking monomer for unsaturated polyester resins, and as a polymerizable plasticizer for many resins. If polymerizes easily, either gradually or rapidly, increasing in viscosity until it finally becomes a clear, infusible solid. The name DAP is used for both the monomeric and polymeric forms. In the partly polymerized form, DAP is used in the production of thermosetting molding powders, casting resins, and laminates. 

Delicate electrical components are often encapsulated or potted by casting a thermosetting liquid resin (usually an epoxy) around them. The casting of acrylic sheet from monomer or syrup is described in Chapter 12. 

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